See attached Instructions Choose one of the psychological disorders covered in chapt

Psychology 2e

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Table of Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter 1: Introduction to Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.1 What Is Psychology? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2 History of Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3 Contemporary Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
1.4 Careers in Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Chapter 2: Psychological Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.1 Why Is Research Important? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.2 Approaches to Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.3 Analyzing Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
2.4 Ethics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Chapter 3: Biopsychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
3.1 Human Genetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.2 Cells of the Nervous System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
3.3 Parts of the Nervous System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.4 The Brain and Spinal Cord . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
3.5 The Endocrine System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Chapter 4: States of Consciousness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
4.1 What Is Consciousness? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
4.2 Sleep and Why We Sleep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
4.3 Stages of Sleep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.4 Sleep Problems and Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
4.5 Substance Use and Abuse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
4.6 Other States of Consciousness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

Chapter 5: Sensation and Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
5.1 Sensation versus Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
5.2 Waves and Wavelengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
5.3 Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
5.4 Hearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
5.5 The Other Senses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
5.6 Gestalt Principles of Perception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Chapter 6: Learning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
6.1 What Is Learning? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
6.2 Classical Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
6.3 Operant Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
6.4 Observational Learning (Modeling) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

Chapter 7: Thinking and Intelligence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
7.1 What Is Cognition? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
7.2 Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
7.3 Problem Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
7.4 What Are Intelligence and Creativity? . . . . . . . . . . . . . . . . . . . . . . . . . . 241
7.5 Measures of Intelligence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
7.6 The Source of Intelligence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252

Chapter 8: Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
8.1 How Memory Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
8.2 Parts of the Brain Involved with Memory . . . . . . . . . . . . . . . . . . . . . . . . . 272
8.3 Problems with Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
8.4 Ways to Enhance Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286

Chapter 9: Lifespan Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
9.1 What Is Lifespan Development? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296

9.2 Lifespan Theories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
9.3 Stages of Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
9.4 Death and Dying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331

Chapter 10: Emotion and Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
10.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
10.2 Hunger and Eating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348
10.3 Sexual Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
10.4 Emotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362

Chapter 11: Personality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
11.1 What Is Personality? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
11.2 Freud and the Psychodynamic Perspective . . . . . . . . . . . . . . . . . . . . . . . 383
11.3 Neo-Freudians: Adler, Erikson, Jung, and Horney . . . . . . . . . . . . . . . . . . . 389
11.4 Learning Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
11.5 Humanistic Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399
11.6 Biological Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400
11.7 Trait Theorists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
11.8 Cultural Understandings of Personality . . . . . . . . . . . . . . . . . . . . . . . . . 406
11.9 Personality Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408

Chapter 12: Social Psychology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
12.1 What Is Social Psychology? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
12.2 Self-presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
12.3 Attitudes and Persuasion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432
12.4 Conformity, Compliance, and Obedience . . . . . . . . . . . . . . . . . . . . . . . . 438
12.5 Prejudice and Discrimination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446
12.6 Aggression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452
12.7 Prosocial Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455

Chapter 13: Industrial-Organizational Psychology . . . . . . . . . . . . . . . . . . . . . . . . . 471
13.1 What Is Industrial and Organizational Psychology? . . . . . . . . . . . . . . . . . . . 472
13.2 Industrial Psychology: Selecting and Evaluating Employees . . . . . . . . . . . . . . 481
13.3 Organizational Psychology: The Social Dimension of Work . . . . . . . . . . . . . . 493
13.4 Human Factors Psychology and Workplace Design . . . . . . . . . . . . . . . . . . 503

Chapter 14: Stress, Lifestyle, and Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511
14.1 What Is Stress? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 512
14.2 Stressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 522
14.3 Stress and Illness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528
14.4 Regulation of Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 541
14.5 The Pursuit of Happiness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 548

Chapter 15: Psychological Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 563
15.1 What Are Psychological Disorders? . . . . . . . . . . . . . . . . . . . . . . . . . . . 564
15.2 Diagnosing and Classifying Psychological Disorders . . . . . . . . . . . . . . . . . . 568
15.3 Perspectives on Psychological Disorders . . . . . . . . . . . . . . . . . . . . . . . . 571
15.4 Anxiety Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 575
15.5 Obsessive-Compulsive and Related Disorders . . . . . . . . . . . . . . . . . . . . . 581
15.6 Posttraumatic Stress Disorder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 585
15.7 Mood Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 588
15.8 Schizophrenia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598
15.9 Dissociative Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
15.10 Disorders in Childhood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
15.11 Personality Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611

Chapter 16: Therapy and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629
16.1 Mental Health Treatment: Past and Present . . . . . . . . . . . . . . . . . . . . . . 630
16.2 Types of Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 636

This OpenStax book is available for free at http://cnx.org/content/col31502/1.4

16.3 Treatment Modalities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648
16.4 Substance-Related and Addictive Disorders: A Special Case . . . . . . . . . . . . . 652
16.5 The Sociocultural Model and Therapy Utilization . . . . . . . . . . . . . . . . . . . . 655

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 759

This OpenStax book is available for free at http://cnx.org/content/col31502/1.4

Preface

Welcome to Psychology 2e, an OpenStax resource. This textbook was written to increase student access to
high-quality learning materials, maintaining highest standards of academic rigor at little to no cost.

ABOUT OPENSTAX

OpenStax is a nonprofit based at Rice University, and it’s our mission to improve student access to
education. Our first openly licensed college textbook was published in 2012, and our library has since
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Through our partnerships with philanthropic foundations and our alliance with other educational
resource organizations, OpenStax is breaking down the most common barriers to learning and
empowering students and instructors to succeed.

ABOUT OPENSTAX RESOURCES
Customization

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means that you can distribute, remix, and build upon the content, as long as you provide attribution to
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Visit the Instructor Resources section of your book page on openstax.org for more information.

Art Attribution in Psychology 2e

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within the caption. Because the art is openly licensed, anyone may reuse the art as long as they provide the
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To maximize readability and content flow, some art does not include attribution in the text. If you reuse art
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Preface 1

ABOUT PSYCHOLOGY 2E

Psychology 2e is designed to meet scope and sequence requirements for the single-semester introduction to
psychology course. The book offers a comprehensive treatment of core concepts, grounded in both classic
studies and current and emerging research. The text also includes coverage of the DSM-5 in examinations
of psychological disorders. Psychology 2e incorporates discussions that reflect the diversity within the
discipline, as well as the diversity of cultures and communities across the globe.

Coverage and scope

The first edition of Psychology has been used by thousands of faculty and hundreds of thousands of
students since its publication in 2015. OpenStax mined our adopters’ extensive and helpful feedback to
identify the most significant revision needs while maintaining the organization that many instructors had
incorporated into their courses. Specific surveys, pre-revision reviews, and customization analysis, as well
as analytical data from OpenStax partners and online learning environments, all aided in planning the
revision.

The result is a book that thoroughly treats psychology’s foundational concepts while adding current and
meaningful coverage in specific areas. Psychology 2e retains its manageable scope and contains ample
features to draw learners into the discipline.

Structurally, the textbook remains similar to the first edition, with no chapter reorganization and very
targeted changes at the section level.

Chapter 1: Introduction to Psychology

Chapter 2: Psychological Research

Chapter 3: Biopsychology

Chapter 4: States of Consciousness

Chapter 5: Sensation and Perception

Chapter 6: Learning

Chapter 7: Thinking and Intelligence

Chapter 8: Memory

Chapter 9: Lifespan Development

Chapter 10: Motivation and Emotion

Chapter 11: Personality

Chapter 12: Social Psychology

Chapter 13: Industrial-Organizational Psychology

Chapter 14: Stress, Lifestyle, and Health

Chapter 15: Psychological Disorders

Chapter 16: Therapy and Treatment

CHANGES TO THE SECOND EDITION

OpenStax only undertakes second editions when significant modifications to the text are necessary. In the
case of Psychology 2e, user feedback indicated that we needed to focus on a few key areas, which we have
done in the following ways.

Content revisions for clarity, accuracy, and currency

The revision plan varied by chapter based on need. Some chapters were significantly updated for
conceptual coverage, research-informed data, and clearer language. In other chapters, the revisions

2 Preface

This OpenStax book is available for free at http://cnx.org/content/col31502/1.4

focused mostly on currency of examples and updates to statistics.

Over 210 new research references have been added or updated in order to improve the scholarly
underpinnings of the material and broaden the perspective for students. Dozens of examples and feature
boxes have been changed or added to better explain concepts and/or increase relevance for students.

Research replication and validity

To engage students in stronger critical analysis and inform them about research reproducibility,
substantial coverage has been added to the research chapter and strategically throughout the textbook
whenever key studies are discussed. This material is presented in a balanced way and provides instructors
with ample opportunity to discuss the importance of replication in a manner that best suits their course.

Diversity, representation, and inclusion

With the help of researchers and teachers who focus on diversity- and identity-related issues, OpenStax
has engaged in detailed diversity reviews to identify opportunities to improve the textbook. Reviewers
were asked to follow a framework to evaluate the book’s terminology, research citations, key contributors
to the field, photos and illustrations, and related aspects, commenting on the representation and
consideration of diverse groups. Significant additions and revisions were made in this regard, and the
review framework itself is available among the OpenStax Psychology 2e instructor resources.

Art and illustrations

Under the guidance of the authors and expert scientific illustrators, especially those well versed in creating
accessible art, the OpenStax team made changes throughout the art program in Psychology 2e.

Accessibility improvements

As with all OpenStax books, the first edition of Psychology was created with a focus on accessibility.
We have emphasized and improved that approach in the second edition. Our goal is to ensure that all
OpenStax websites and the web view versions of our learning materials follow accessible web design best
practices, so that they will meet the W3C-WAI Web Content Accessibility Guidelines (WCAG) 2.0 at Level
AA and Section 508 of the Rehabilitation Act. The WCAG 2.0 guidelines explain ways to make web content
more accessible for people with disabilities and more user-friendly for everyone.

To accommodate users of specific assistive technologies, all alternative text was reviewed and
revised for comprehensiveness and clarity.

All illustrations were revised to improve the color contrast, which is important for some visually
impaired students.

Overall, the OpenStax platform has been continually upgraded to improve accessibility.

To learn more about our commitment and progress, please view our accessibility statement
(https://openstax.org/accessibility-statement) .

A transition guide will be available on openstax.org to highlight the specific chapter-level changes to the
second edition.

Pedagogical foundation

Psychology 2e engages students through inquiry, self-reflection, and investigation. Features in the second
edition have been carefully updated to remain topical and relevant while deepening students’ relationship
to the material. They include the following:

Everyday Connection features tie psychological topics to everyday issues and behaviors that
students encounter in their lives and the world. Topics include the validity of scores on college

Preface 3

entrance exams, the opioid crisis, the impact of social status on stress and healthcare, and cognitive
mapping.

What Do You Think? features provide research-based information and ask students their views
on controversial issues. Topics include “Brain Dead and on Life Support,” “Violent Media and
Aggression,” and “Capital Punishment and Criminals with Intellectual Disabilities.”

Dig Deeper features discuss one specific aspect of a topic in greater depth so students can dig more
deeply into the concept. Examples include discussions on the distinction between evolutionary
psychology and behavioral genetics, recent findings on neuroplasticity, the field of forensic
psychology, and a presentation of research on strategies for coping with prejudice and
discrimination.

Connect the Concepts features revisit a concept learned in another chapter, expanding upon it
within a different context. Features include “Emotional Expression and Emotional Regulation,”
“Tweens, Teens, and Social Norms,” and “Conditioning and OCD.”

Art, interactives, and assessments that engage

Our art program is designed to enhance students’ understanding of psychological concepts through
simple, effective graphs, diagrams, and photographs. Psychology 2e also incorporates links to relevant
interactive exercises and animations that help bring topics to life. Selected assessment items touch directly
on students’ lives.

Link to Learning features direct students to online interactive exercises and animations that add a
fuller context to core content and provide an opportunity for application.

Personal Application Questions engage students in topics at a personal level to encourage
reflection and promote discussion.

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4 Preface

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ABOUT THE AUTHORS
Senior contributing authors

Rose M. Spielman (Content Lead)
Dr. Rose Spielman has been teaching psychology and working as a licensed clinical psychologist for
20 years. Her academic career has included positions at Quinnipiac University, Housatonic Community
College, and Goodwin College. As a licensed clinical psychologist, educator, and volunteer director, Rose
is able to connect with people from diverse backgrounds and facilitate treatment, advocacy, and education.
In her years of work as a teacher, therapist, and administrator, she has helped thousands of students
and clients and taught them to advocate for themselves and move their lives forward to become more
productive citizens and family members.

William J. Jenkins, Mercer University
Marilyn D. Lovett, Spelman College

Contributing Authors

Mara Aruguete, Lincoln University
Laura Bryant, Eastern Gateway Community College
Barbara Chappell, Walden University
Kathryn Dumper, Bainbridge State College
Arlene Lacombe, Saint Joseph’s University
Julie Lazzara, Paradise Valley Community College
Tammy McClain, West Liberty University
Barbara B. Oswald, Miami University
Marion Perlmutter, University of Michigan
Mark D. Thomas, Albany State University

Reviewers

Patricia G. Adams, Pitt Community College
Daniel Bellack, Trident Technical College
Christopher M. Bloom, Providence College
Jerimy Blowers, Cayuga Community College
Salena Brody, Collin College
David A. Caicedo, Borough of Manhattan Community College, CUNY
Bettina Casad, University of Missouri–St. Louis
Sharon Chacon, Northeast Wisconsin Technical College
James Corpening
Frank Eyetsemitan, Roger Williams University
Tamara Ferguson, Utah State University
Kathleen Flannery, Saint Anselm College
Johnathan Forbey, Ball State University
Laura Gaudet, Chadron State College
William Goggin, University of Southern Mississippi
Jeffery K. Gray, Charleston Southern University
Heather Griffiths, Fayetteville State University
Mark Holder, University of British Columbia
Rita Houge, Des Moines Area Community College
Colette Jacquot, Strayer University
John Johanson, Winona State University
Andrew Johnson, Park University
Shaila Khan, Tougaloo College

Preface 5

Cynthia Kreutzer, Georgia State University Perimeter College at Clarkston Campus
Carol Laman, Houston Community College
Dana C. Leighton, Texas A&M University—Texarkana
Thomas Malloy, Rhode Island College
Jan Mendoza, Golden West College
Christopher Miller, University of Minnesota
Lisa Moeller, Beckfield College
Amy T. Nusbaum, Heritage University
Jody Resko, Queensborough Community College (CUNY)
Hugh Riley, Baylor University
Juan Salinas, University of Texas at Austin
Brittney Schrick, Southern Arkansas University
Phoebe Scotland, College of the Rockies
Christine Selby, Husson University
Sally B. Seraphin, Centre College
Brian Sexton, Kean University
Nancy Simpson, Trident Technical College
Jason M. Smith, Federal Bureau of Prisons – FCC Hazelton
Robert Stennett, University of Georgia
Jennifer Stevenson, Ursinus College
Eric Weiser, Curry College
Jay L. Wenger, Harrisburg Area Community College
Alan Whitehead, Southern Virginia University
Valjean Whitlow, American Public University
Rachel Wu, University of California, Riverside
Alexandra Zelin, University of Tennessee at Chattanooga

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Chapter 1

Introduction to Psychology

Figure 1.1 Psychology is the scientific study of mind and behavior. (credit “background”: modification of work by
Nattachai Noogure; credit “top left”: modification of work by U.S. Navy; credit “top middle-left”: modification of work by
Peter Shanks; credit “top middle-right”: modification of work by “devinf”/Flickr; credit “top right”: modification of work
by Alejandra Quintero Sinisterra; credit “bottom left”: modification of work by Gabriel Rocha; credit “bottom middle-
left”: modification of work by Caleb Roenigk; credit “bottom middle-right”: modification of work by Staffan Scherz;
credit “bottom right”: modification of work by Czech Provincial Reconstruction Team)

Chapter Outline

1.1 What Is Psychology?

1.2 History of Psychology

1.3 Contemporary Psychology

1.4 Careers in Psychology

Introduction

Clive Wearing is an accomplished musician who lost his ability to form new memories when he became
sick at the age of 46. While he can remember how to play the piano perfectly, he cannot remember what
he ate for breakfast just an hour ago (Sacks, 2007). James Wannerton experiences a taste sensation that is
associated with the sound of words. His former girlfriend’s name tastes like rhubarb (Mundasad, 2013).
John Nash is a brilliant mathematician and Nobel Prize winner. However, while he was a professor at MIT,
he would tell people that the New York Times contained coded messages from extraterrestrial beings that
were intended for him. He also began to hear voices and became suspicious of the people around him.
Soon thereafter, Nash was diagnosed with schizophrenia and admitted to a state-run mental institution
(O’Connor & Robertson, 2002). Nash was the subject of the 2001 movie A Beautiful Mind. Why did these
people have these experiences? How does the human brain work? And what is the connection between
the brain’s internal processes and people’s external behaviors? This textbook will introduce you to various
ways that the field of psychology has explored these questions.

Chapter 1 | Introduction to Psychology 7

1.1 What Is Psychology?

Learning Objectives

By the end of this section, you will be able to:
• Define psychology
• Understand the merits of an education in psychology

What is creativity? Why do some people become homeless? What are prejudice and discrimination? What
is consciousness? The field of psychology explores questions like these. Psychology refers to the scientific
study of the mind and behavior. Psychologists use the scientific method to acquire knowledge. To apply
the scientific method, a researcher with a question about how or why something happens will propose
a tentative explanation, called a hypothesis, to explain the phenomenon. A hypothesis should fit into the
context of a scientific theory, which is a broad explanation or group of explanations for some aspect of the
natural world that is consistently supported by evidence over time. A theory is the best understanding we
have of that part of the natural world. The researcher then makes observations or carries out an experiment
to test the validity of the hypothesis. Those results are then published or presented at research conferences
so that others can replicate or build on the results.

Scientists test that which is perceivable and measurable. For example, the hypothesis that a bird sings
because it is happy is not a hypothesis that can be tested since we have no way to measure the happiness
of a bird. We must ask a different question, perhaps about the brain state of the bird, since this can be
measured. However, we can ask individuals about whether they sing because they are happy since they
are able to tell us. Thus, psychological science is empirical, based on measurable data.

In general, science deals only with matter and energy, that is, those things that can be measured, and it
cannot arrive at knowledge about values and morality. This is one reason why our scientific understanding
of the mind is so limited, since thoughts, at least as we experience them, are neither matter nor energy. The
scientific method is also a form of empiricism. An empirical method for acquiring knowledge is one based
on observation, including experimentation, rather than a method based only on forms of logical argument
or previous authorities.

It was not until the late 1800s that psychology became accepted as its own academic discipline. Before this
time, the workings of the mind were considered under the auspices of philosophy. Given that any behavior
is, at its roots, biological, some areas of psychology take on aspects of a natural science like biology. No
biological organism exists in isolation, and our behavior is influenced by our interactions with others.
Therefore, psychology is also a social science.

WHY STUDY PSYCHOLOGY?

Often, students take their first psychology course because they are interested in helping others and want
to learn more about themselves and why they act the way they do. Sometimes, students take a psychology
course because it either satisfies a general education requirement or is required for a program of study
such as nursing or pre-med. Many of these students develop such an interest in the area that they go
on to declare psychology as their major. As a result, psychology is one of the most popular majors on
college campuses across the United States (Johnson & Lubin, 2011). A number of well-known individuals
were psychology majors. Just a few famous names on this list are Facebook’s creator Mark Zuckerberg,
television personality and political satirist Jon Stewart, actress Natalie Portman, and filmmaker Wes
Craven (Halonen, 2011). About 6 percent of all bachelor degrees granted in the United States are in the
discipline of psychology (U.S. Department of Education, 2016).

An education in psychology is valuable for a number of reasons. Psychology students hone critical
thinking skills and are trained in the use of the scientific method. Critical thinking is the active application
of a set of skills to information for the understanding and evaluation of that information. The evaluation

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of information—assessing its reliability and usefulness— is an important skill in a world full of competing
“facts,” many of which are designed to be misleading. For example, critical thinking involves maintaining
an attitude of skepticism, recognizing internal biases, making use of logical thinking, asking appropriate
questions, and making observations. Psychology students also can develop better communication skills
during the course of their undergraduate coursework (American Psychological Association, 2011).
Together, these factors increase students’ scientific literacy and prepare students to critically evaluate the
various sources of information they encounter.

In addition to these broad-based skills, psychology students come to understand the complex factors
that shape one’s behavior. They appreciate the interaction of our biology, our environment, and our
experiences in determining who we are and how we will behave. They learn about basic principles that
guide how we think and behave, and they come to recognize the tremendous diversity that exists across
individuals and across cultural boundaries (American Psychological Association, 2011).

Watch a brief video about some questions to consider before deciding to major in psychology
(http://openstax.org/l/psycmajor) to learn more.

1.2 History of Psychology

Learning Objectives

By the end of this section, you will be able to:
• Understand the importance of Wundt and James in the development of psychology
• Appreciate Freud’s influence on psychology
• Understand the basic tenets of Gestalt psychology
• Appreciate the important role that behaviorism played in psychology’s history
• Understand basic tenets of humanism
• Understand how the cognitive revolution shifted psychology’s focus back to the mind

Psychology is a relatively young science with its experimental roots in the 19th century, compared, for
example, to human physiology, which dates much earlier. As mentioned, anyone interested in exploring
issues related to the mind generally did so in a philosophical context prior to the 19th century. Two
19th century scholars, Wilhelm Wundt and William James, are generally credited as being the founders
of psychology as a science and academic discipline that was distinct from philosophy. This section will
provide an overview of the shifts in paradigms that have influenced psychology from Wundt and James
through today.

WUNDT AND STRUCTURALISM

Wilhelm Wundt (1832–1920) was a German scientist who was the first person to be referred to as a
psychologist. His famous book entitled Principles of Physiological Psychology was published in 1873. Wundt
viewed psychology as a scientific study of conscious experience, and he believed that the goal of
psychology was to identify components of consciousness and how those components combined to result
in our conscious experience. Wundt used introspection (he called it “internal perception”), a process by
which someone examines their own conscious experience as objectively as possible, making the human
mind like any other aspect of nature that a scientist observed. He believed in the notion of

LINK TO LEARNING

Chapter 1 | Introduction to Psychology 9

voluntarism—that people have free will and should know the intentions of a psychological experiment
if they were participating (Danziger, 1980). Wundt considered his version experimental introspection;
he used instruments such as those that measured reaction time. He also wrote Volkerpsychologie in 1904
in which he suggested that psychology should include the study of culture, as it involves the study of
people. Edward Titchener, one of his students, went on to develop structuralism. Its focus was on the
contents of mental processes rather than their function (Pickren & Rutherford, 2010). Wundt established
his psychology laboratory at the University at Leipzig in 1879 (Figure 1.2). In this laboratory, Wundt
and his students conducted experiments on, for example, reaction times. A subject, sometimes in a room
isolated from the scientist, would receive a stimulus such as a light, image, or sound. The subject’s reaction
to the stimulus would be to push a button, and an apparatus would record the time to reaction. Wundt
could measure reaction time to one-thousandth of a second (Nicolas & Ferrand, 1999).

Figure 1.2 (a) Wilhelm Wundt is credited as one of the founders of psychology. He created the first laboratory for
psychological research. (b) This photo shows him seated and surrounded by fellow researchers and equipment in his
laboratory in Germany.

However, despite his efforts to train individuals in the process of introspection, this process remained
highly subjective, and there was very little agreement between individuals.

JAMES AND FUNCTIONALISM

William James (1842–1910) was the first American psychologist who espoused a different perspective on
how psychology should operate (Figure 1.3). James was introduced to Darwin’s theory of evolution by
natural selection and accepted it as an explanation of an organism’s characteristics. Key to that theory is
the idea that natural selection leads to organisms that are adapted to their environment, including their
behavior. Adaptation means that a trait of an organism has a function for the survival and reproduction
of the individual, because it has been naturally selected. As James saw it, psychology’s purpose was to
study the function of behavior in the world, and as such, his perspective was known as functionalism.
Functionalism focused on how mental activities helped an organism fit into its environment.
Functionalism has a second, more subtle meaning in that functionalists were more interested in the
operation of the whole mind rather than of its individual parts, which were the focus of structuralism. Like
Wundt, James believed that introspection could serve as one means by which someone might study mental
activities, but James also relied on more objective measures, including the use of various recording devices,
and examinations of concrete products of mental activities and of anatomy and physiology (Gordon, 1995).

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Figure 1.3 William James, shown here in a self-portrait, was the first American psychologist.

FREUD AND PSYCHOANALYTIC THEORY

Perhaps one of the most influential and well-known figures in psychology’s history was Sigmund Freud
(Figure 1.4). Freud (1856–1939) was an Austrian neurologist who was fascinated by patients suffering
from “hysteria” and neurosis. Hysteria was an ancient diagnosis for disorders, primarily of women with
a wide variety of symptoms, including physical symptoms and emotional disturbances, none of which
had an apparent physical cause. Freud theorized that many of his patients’ problems arose from the
unconscious mind. In Freud’s view, the unconscious mind was a repository of feelings and urges of which
we have no awareness. Gaining access to the unconscious, then, was crucial to the successful resolution
of the patient’s problems. According to Freud, the unconscious mind could be accessed through dream
analysis, by examinations of the first words that came to people’s minds, and through seemingly innocent
slips of the tongue. Psychoanalytic theory focuses on the role of a person’s unconscious, as well as early
childhood experiences, and this particular perspective dominated clinical psychology for several decades
(Thorne & Henley, 2005).

Figure 1.4 (a) Sigmund Freud was a highly influential figure in the history of psychology. (b) One of his many books,
A General Introduction to Psychoanalysis, shared his ideas about psychoanalytical therapy; it was published in 1922.

Chapter 1 | Introduction to Psychology 11

Freud’s ideas were influential, and you will learn more about them when you study lifespan development,
personality, and therapy. For instance, many therapists believe strongly in the unconscious and the
impact of early childhood experiences on the rest of a person’s life. The method of psychoanalysis, which
involves the patient talking about their experiences and selves, while not invented by Freud, was certainly
popularized by him and is still used today. Many of Freud’s other ideas, however, are controversial.
Drew Westen (1998) argues that many of the criticisms of Freud’s ideas are misplaced, in that they
attack his older ideas without taking into account later writings. Westen also argues that critics fail to
consider the success of the broad ideas that Freud introduced or developed, such as the importance
of childhood experiences in adult motivations, the role of unconscious versus conscious motivations in
driving our behavior, the fact that motivations can cause conflicts that affect behavior, the effects of mental
representations of ourselves and others in guiding our interactions, and the development of personality
over time. Westen identifies subsequent research support for all of these ideas.

More modern iterations of Freud’s clinical approach have been empirically demonstrated to be effective
(Knekt et al., 2008; Shedler, 2010). Some current practices in psychotherapy involve examining unconscious
aspects of the self and relationships, often through the relationship between the therapist and the client.
Freud’s historical significance and contributions to clinical practice merit his inclusion in a discussion of
the historical movements within psychology.

WERTHEIMER, KOFFKA, KÖHLER, AND GESTALT PSYCHOLOGY

Max Wertheimer (1880–1943), Kurt Koffka (1886–1941), and Wolfgang Köhler (1887–1967) were three
German psychologists who immigrated to the United States in the early 20th century to escape Nazi
Germany. These scholars are credited with introducing psychologists in the United States to various
Gestalt principles. The word Gestalt roughly translates to “whole;” a major emphasis of Gestalt
psychology deals with the fact that although a sensory experience can be broken down into individual
parts, how those parts relate to each other as a whole is often what the individual responds to in
perception. For example, a song may be made up of individual notes played by different instruments, but
the real nature of the song is perceived in the combinations of these notes as they form the melody, rhythm,
and harmony. In many ways, this particular perspective would have directly contradicted Wundt’s ideas
of structuralism (Thorne & Henley, 2005).

Unfortunately, in moving to the United States, these scientists were forced to abandon much of their
work and were unable to continue to conduct research on a large scale. These factors along with the
rise of behaviorism (described next) in the United States prevented principles of Gestalt psychology from
being as influential in the United States as they had been in their native Germany (Thorne & Henley,
2005). Despite these issues, several Gestalt principles are still very influential today. Considering the
human individual as a whole rather than as a sum of individually measured parts became an important
foundation in humanistic theory late in the century. The ideas of Gestalt have continued to influence
research on sensation and perception.

Structuralism, Freud, and the Gestalt psychologists were all concerned in one way or another with
describing and understanding inner experience. But other researchers had concerns that inner experience
could be a legitimate subject of scientific inquiry and chose instead to exclusively study behavior, the
objectively observable outcome of mental processes.

PAVLOV, WATSON, SKINNER, AND BEHAVIORISM

Early work in the field of behavior was conducted by the Russian physiologist Ivan Pavlov (1849–1936).
Pavlov studied a form of learning behavior called a conditioned reflex, in which an animal or human
produced a reflex (unconscious) response to a stimulus and, over time, was conditioned to produce the
response to a different stimulus that the experimenter associated with the original stimulus. The reflex
Pavlov worked with was salivation in response to the presence of food. The salivation reflex could be
elicited using a second stimulus, such as a specific sound, that was presented in association with the

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initial food stimulus several times. Once the response to the second stimulus was “learned,” the food
stimulus could be omitted. Pavlov’s “classical conditioning” is only one form of learning behavior studied
by behaviorists.

John B. Watson (1878–1958) was an influential American psychologist whose most famous work occurred
during the early 20th century at Johns Hopkins University (Figure 1.5). While Wundt and James were
concerned with understanding conscious experience, Watson thought that the study of consciousness
was flawed. Because he believed that objective analysis of the mind was impossible, Watson preferred to
focus directly on observable behavior and try to bring that behavior under control. Watson was a major
proponent of shifting the focus of psychology from the mind to behavior, and this approach of observing
and controlling behavior came to be known as behaviorism. A major object of study by behaviorists was
learned behavior and its interaction with inborn qualities of the organism. Behaviorism commonly used
animals in experiments under the assumption that what was learned using animal models could, to some
degree, be applied to human behavior. Indeed, Tolman (1938) stated, “I believe that everything important
in psychology (except … such matters as involve society and words) can be investigated in essence through
the continued experimental and theoretical analysis of the determiners of rat behavior at a choice-point in
a maze.”

Figure 1.5 John B. Watson is known as the father of behaviorism within psychology.

Behaviorism dominated experimental psychology for several decades, and its influence can still be felt
today (Thorne & Henley, 2005). Behaviorism is largely responsible for establishing psychology as a
scientific discipline through its objective methods and especially experimentation. In addition, it is used
in behavioral and cognitive-behavioral therapy. Behavior modification is commonly used in classroom
settings. Behaviorism has also led to research on environmental influences on human behavior.

B. F. Skinner (1904–1990) was an American psychologist (Figure 1.6). Like Watson, Skinner was a
behaviorist, and he concentrated on how behavior was affected by its consequences. Therefore, Skinner
spoke of reinforcement and punishment as major factors in driving behavior. As a part of his research,
Skinner developed a chamber that allowed the careful study of the principles of modifying behavior
through reinforcement and punishment. This device, known as an operant conditioning chamber (or more
familiarly, a Skinner box), has remained a crucial resource for researchers studying behavior (Thorne &
Henley, 2005).

Chapter 1 | Introduction to Psychology 13

Figure 1.6 (a) B. F. Skinner is famous for his research on operant conditioning. (b) Modified versions of the operant
conditioning chamber, or Skinner box, are still widely used in research settings today. (credit a: modification of work
by “Silly rabbit”/Wikimedia Commons)

The Skinner box is a chamber that isolates the subject from the external environment and has a behavior
indicator such as a lever or a button. When the animal pushes the button or lever, the box is able to
deliver a positive reinforcement of the behavior (such as food) or a punishment (such as a noise) or a token
conditioner (such as a light) that is correlated with either the positive reinforcement or punishment.

Skinner’s focus on positive and negative reinforcement of learned behaviors had a lasting influence in
psychology that has waned somewhat since the growth of research in cognitive psychology. Despite
this, conditioned learning is still used in human behavioral modification. Skinner’s two widely read and
controversial popular science books about the value of operant conditioning for creating happier lives
remain as thought-provoking arguments for his approach (Greengrass, 2004).

MASLOW, ROGERS, AND HUMANISM

During the early 20th century, American psychology was dominated by behaviorism and psychoanalysis.
However, some psychologists were uncomfortable with what they viewed as limited perspectives being
so influential to the field. They objected to the pessimism and determinism (all actions driven by the
unconscious) of Freud. They also disliked the reductionism, or simplifying nature, of behaviorism.
Behaviorism is also deterministic at its core, because it sees human behavior as entirely determined by
a combination of genetics and environment. Some psychologists began to form their own ideas that
emphasized personal control, intentionality, and a true predisposition for “good” as important for our self-
concept and our behavior. Thus, humanism emerged. Humanism is a perspective within psychology that
emphasizes the potential for good that is innate to all humans. Two of the most well-known proponents of
humanistic psychology are Abraham Maslow and Carl Rogers (O’Hara, n.d.).

Abraham Maslow (1908–1970) was an American psychologist who is best known for proposing a hierarchy
of human needs in motivating behavior (Figure 1.7). Although this concept will be discussed in more
detail in a later chapter, a brief overview will be provided here. Maslow asserted that so long as basic needs
necessary for survival were met (e.g., food, water, shelter), higher-level needs (e.g., social needs) would
begin to motivate behavior. According to Maslow, the highest-level needs relate to self-actualization, a
process by which we achieve our full potential. Obviously, the focus on the positive aspects of human
nature that are characteristic of the humanistic perspective is evident (Thorne & Henley, 2005). Humanistic
psychologists rejected, on principle, the research approach based on reductionist experimentation in the
tradition of the physical and biological sciences, because it missed the “whole” human being. Beginning
with Maslow and Rogers, there was an insistence on a humanistic research program. This program
has been largely qualitative (not measurement-based), but there exist a number of quantitative research
strains within humanistic psychology, including research on happiness, self-concept, meditation, and the
outcomes of humanistic psychotherapy (Friedman, 2008).

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Figure 1.7 Maslow’s hierarchy of needs is shown.

Carl Rogers (1902–1987) was also an American psychologist who, like Maslow, emphasized the potential
for good that exists within all people (Figure 1.8). Rogers used a therapeutic technique known as client-
centered therapy in helping his clients deal with problematic issues that resulted in their seeking
psychotherapy. Unlike a psychoanalytic approach in which the therapist plays an important role in
interpreting what conscious behavior reveals about the unconscious mind, client-centered therapy
involves the patient taking a lead role in the therapy session. Rogers believed that a therapist needed to
display three features to maximize the effectiveness of this particular approach: unconditional positive
regard, genuineness, and empathy. Unconditional positive regard refers to the fact that the therapist
accepts their client for who they are, no matter what he or she might say. Provided these factors, Rogers
believed that people were more than capable of dealing with and working through their own issues
(Thorne & Henley, 2005).

Figure 1.8 Carl Rogers, shown in this portrait, developed a client-centered therapy method that has been influential
in clinical settings. (credit: “Didius”/Wikimedia Commons)

Humanism has been influential to psychology as a whole. Both Maslow and Rogers are well-known names

Chapter 1 | Introduction to Psychology 15

among students of psychology (you will read more about both later in this text), and their ideas have
influenced many scholars. Furthermore, Rogers’ client-centered approach to therapy is still commonly
used in psychotherapeutic settings today (O’hara, n.d.)

View a brief video of Carl Rogers describing his therapeutic approach (http://openstax.org/l/
crogers1) to learn more.

THE COGNITIVE REVOLUTION

Behaviorism’s emphasis on objectivity and focus on external behavior had pulled psychologists’ attention
away from the mind for a prolonged period of time. The early work of the humanistic psychologists
redirected attention to the individual human as a whole, and as a conscious and self-aware being. By the
1950s, new disciplinary perspectives in linguistics, neuroscience, and computer science were emerging,
and these areas revived interest in the mind as a focus of scientific inquiry. This particular perspective
has come to be known as the cognitive revolution (Miller, 2003). By 1967, Ulric Neisser published the first
textbook entitled Cognitive Psychology, which served as a core text in cognitive psychology courses around
the country (Thorne & Henley, 2005).

Although no one person is entirely responsible for starting the cognitive revolution, Noam Chomsky
was very influential in the early days of this movement (Figure 1.9). Chomsky (1928–), an American
linguist, was dissatisfied with the influence that behaviorism had had on psychology. He believed that
psychology’s focus on behavior was short-sighted and that the field had to re-incorporate mental
functioning into its purview if it were to offer any meaningful contributions to understanding behavior
(Miller, 2003).

Figure 1.9 Noam Chomsky was very influential in beginning the cognitive revolution. In 2010, this mural honoring
him was put up in Philadelphia, Pennsylvania. (credit: Robert Moran)

European psychology had never really been as influenced by behaviorism as had American psychology;
and thus, the cognitive revolution helped reestablish lines of communication between European
psychologists and their American counterparts. Furthermore, psychologists began to cooperate with
scientists in other fields, like anthropology, linguistics, computer science, and neuroscience, among others.
This interdisciplinary approach often was referred to as the cognitive sciences, and the influence and
prominence of this particular perspective resonates in modern-day psychology (Miller, 2003).

LINK TO LEARNING

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Feminist Psychology

The science of psychology has had an impact on human wellbeing, both positive and negative. The dominant
influence of Western, white, and male academics in the early history of psychology meant that psychology
developed with the biases inherent in those individuals, which often had negative consequences for members
of society who were not white or male. Women, members of ethnic minorities in both the United States
and other countries, and individuals with sexual orientations other than straight had difficulties entering the
field of psychology and therefore influencing its development. They also suffered from the attitudes of white
male psychologists who were not immune to the nonscientific attitudes prevalent in the society in which they
developed and worked. Until the 1960s, the science of psychology was largely a “womanless” psychology
(Crawford & Marecek, 1989), meaning that few women were able to practice psychology, so they had little
influence on what was studied. In addition, the experimental subjects of psychology were mostly men, which
resulted from underlying assumptions that gender had no influence on psychology and that women were not
of sufficient interest to study.

An article by Naomi Weisstein, first published in 1968 (Weisstein, 1993), stimulated a feminist revolution
in psychology by presenting a critique of psychology as a science. She also specifically criticized male
psychologists for constructing the psychology of women entirely out of their own cultural biases and without
careful experimental tests to verify any of their characterizations of women. Weisstein used, as examples,
statements by prominent psychologists in the 1960s, such as this quote by Bruno Bettleheim: “We must start
with the realization that, as much as women want to be good scientists or engineers, they want first and
foremost to be womanly companions of men and to be mothers.” Weisstein’s critique formed the foundation
for the subsequent development of a feminist psychology that attempted to be free of the influence of male
cultural biases on our knowledge of the psychology of women.

Crawford & Marecek (1989) identify several feminist approaches to psychology that can be described as
feminist psychology. These include re-evaluating and discovering the contributions of women to the history
of psychology, studying psychological gender differences, and questioning the male bias present across the
practice of the scientific approach to knowledge.

MULTICULTURAL AND CROSS-CULTURAL PSYCHOLOGY

Culture has important impacts on individuals and social psychology, yet the effects of culture on
psychology are under-studied. There is a risk that psychological theories and data derived from white,
American settings could be assumed to apply to individuals and social groups from other cultures and this
is unlikely to be true (Betancourt & López, 1993). One weakness in the field of cross-cultural psychology
is that in looking for differences in psychological attributes across cultures, there remains a need to go
beyond simple descriptive statistics (Betancourt & López, 1993). In this sense, it has remained a descriptive
science, rather than one seeking to determine cause and effect. For example, a study of characteristics
of individuals seeking treatment for a binge eating disorder in Hispanic American, African American,
and Caucasian American individuals found significant differences between groups (Franko et al., 2012).
The study concluded that results from studying any one of the groups could not be extended to the
other groups, and yet potential causes of the differences were not measured. Multicultural psychologists
develop theories and conduct research with diverse populations, typically within one country. Cross-
cultural psychologists compare populations across countries, such as participants from the United States
compared to participants from China.

In 1920, Francis Cecil Sumner was the first African American to receive a PhD in psychology in the United
States. Sumner established a psychology degree program at Howard University, leading to the education
of a new generation of African American psychologists (Black, Spence, and Omari, 2004). Much of the
work of early psychologists from diverse backgrounds was dedicated to challenging intelligence testing
and promoting innovative educational methods for children. George I. Sanchez contested such testing with

DIG DEEPER

Chapter 1 | Introduction to Psychology 17

Mexican American children. As a psychologist of Mexican heritage, he pointed out that the language and
cultural barriers in testing were keeping children from equal opportunities (Guthrie, 1998). By 1940, he was
teaching with his doctoral degree at University of Texas at Austin and challenging segregated educational
practices (Romo, 1986).

Two famous African American researchers and psychologists are Mamie Phipps Clark and her husband,
Kenneth Clark. They are best known for their studies conducted on African American children and doll
preference, research that was instrumental in the Brown v. Board of Education Supreme Court desegregation
case. The Clarks applied their research to social services and opened the first child guidance center in
Harlem (American Psychological Association, 2019).

Listen to the podcast below describing the Clarks’ research and impact on the Supreme Court decision.

Listen to a podcast about the influence of an African American’s psychology research on the
historic Brown v. Board of Education civil rights case (http://openstax.org/l/crogers2) to learn more.

The American Psychological Association has several ethnically based organizations for professional
psychologists that facilitate interactions among members. Since psychologists belonging to specific ethnic
groups or cultures have the most interest in studying the psychology of their communities, these
organizations provide an opportunity for the growth of research on the interplay between culture and
psychology.

WOMEN IN PSYCHOLOGY

Although rarely given credit, women have been contributing to psychology since its inception as a field of
study. In 1894, Margaret Floy Washburn was the first woman awarded the doctoral degree in psychology.
She wrote The Animal Mind: A Textbook of Comparative Psychology, and it was the standard in the field for
over 20 years. In the mid 1890s, Mary Whiton Calkins completed all requirements toward the PhD in
psychology, but Harvard University refused to award her that degree because she was a woman. She had
been taught and mentored by William James, who tried and failed to convince Harvard to award her the
doctoral degree. Her memory research studied primacy and recency (Madigan & O’Hara, 1992), and she
also wrote about how structuralism and functionalism both explained self-psychology (Calkins, 1906).

Another influential woman, Mary Cover Jones, conducted a study she considered to be a sequel to
John B. Watson’s study of Little Albert (you’ll learn about this study in the chapter on Learning). Jones
unconditioned fear in Little Peter, who had been afraid of rabbits (Jones, 1924).

Ethnic minority women contributing to the field of psychology include Martha Bernal and Inez Beverly
Prosser; their studies were related to education. Bernal, the first Latina to earn her doctoral degree in
psychology (1962) conducted much of her research with Mexican American children. Prosser was the first
African American woman awarded the PhD in 1933 at the University of Cincinnati (Benjamin, Henry, &
McMahon, 2005).

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1.3 Contemporary Psychology

Learning Objectives

By the end of this section, you will be able to:
• Appreciate the diversity of interests and foci within psychology
• Understand basic interests and applications in each of the described areas of psychology
• Demonstrate familiarity with some of the major concepts or important figures in each of the

described areas of psychology

Contemporary psychology is a diverse field that is influenced by all of the historical perspectives described
in the preceding section. Reflective of the discipline’s diversity is the diversity seen within the American
Psychological Association (APA). The APA is a professional organization representing psychologists in
the United States. The APA is the largest organization of psychologists in the world, and its mission is to
advance and disseminate psychological knowledge for the betterment of people. There are 56 divisions
within the APA, representing a wide variety of specialties that range from Societies for the Psychology of
Religion and Spirituality to Exercise and Sport Psychology to Behavioral Neuroscience and Comparative
Psychology. Reflecting the diversity of the field of psychology itself, members, affiliate members, and
associate members span the spectrum from students to doctoral-level psychologists, and come from a
variety of places including educational settings, criminal justice, hospitals, the armed forces, and industry
(American Psychological Association, 2014). G. Stanley Hall was the first president of the APA. Before
he earned his doctoral degree, he was an adjunct instructor at Wilberforce University, a historically
black college/university (HBCU), while serving as faculty at Antioch College. Hall went on to work
under William James, earning his PhD. Eventually, he became the first president of Clark University in
Massachusetts when it was founded (Pickren & Rutherford, 2010).

The Association for Psychological Science (APS) was founded in 1988 and seeks to advance the scientific
orientation of psychology. Its founding resulted from disagreements between members of the scientific
and clinical branches of psychology within the APA. The APS publishes five research journals and
engages in education and advocacy with funding agencies. A significant proportion of its members
are international, although the majority is located in the United States. Other organizations provide
networking and collaboration opportunities for professionals of several ethnic or racial groups working
in psychology, such as the National Latina/o Psychological Association (NLPA), the Asian American
Psychological Association (AAPA), the Association of Black Psychologists (ABPsi), and the Society of
Indian Psychologists (SIP). Most of these groups are also dedicated to studying psychological and social
issues within their specific communities.

This section will provide an overview of the major subdivisions within psychology today in the order
in which they are introduced throughout the remainder of this textbook. This is not meant to be an
exhaustive listing, but it will provide insight into the major areas of research and practice of modern-day
psychologists.

Please visit this website about the divisions within the APA (http://openstax.org/l/biopsychology) to
learn more.

View these student resources (http://openstax.org/l/studentresource) also provided by the APA.

LINK TO LEARNING

Chapter 1 | Introduction to Psychology 19

BIOPSYCHOLOGY AND EVOLUTIONARY PSYCHOLOGY

As the name suggests, biopsychology explores how our biology influences our behavior. While biological
psychology is a broad field, many biological psychologists want to understand how the structure and
function of the nervous system is related to behavior (Figure 1.10). As such, they often combine the
research strategies of both psychologists and physiologists to accomplish this goal (as discussed in Carlson,
2013).

Figure 1.10 Biological psychologists study how the structure and function of the nervous system generate behavior.

The research interests of biological psychologists span a number of domains, including but not limited
to, sensory and motor systems, sleep, drug use and abuse, ingestive behavior, reproductive behavior,
neurodevelopment, plasticity of the nervous system, and biological correlates of psychological disorders.
Given the broad areas of interest falling under the purview of biological psychology, it will probably
come as no surprise that individuals from all sorts of backgrounds are involved in this research, including
biologists, medical professionals, physiologists, and chemists. This interdisciplinary approach is often
referred to as neuroscience, of which biological psychology is a component (Carlson, 2013).

While biopsychology typically focuses on the immediate causes of behavior based in the physiology of a
human or other animal, evolutionary psychology seeks to study the ultimate biological causes of behavior.
To the extent that a behavior is impacted by genetics, a behavior, like any anatomical characteristic of a
human or animal, will demonstrate adaption to its surroundings. These surroundings include the physical
environment and, since interactions between organisms can be important to survival and reproduction, the
social environment. The study of behavior in the context of evolution has its origins with Charles Darwin,
the co-discoverer of the theory of evolution by natural selection. Darwin was well aware that behaviors
should be adaptive and wrote books titled, The Descent of Man (1871) and The Expression of the Emotions in
Man and Animals (1872), to explore this field.

Evolutionary psychology, and specifically, the evolutionary psychology of humans, has enjoyed a
resurgence in recent decades. To be subject to evolution by natural selection, a behavior must have a
significant genetic cause. In general, we expect all human cultures to express a behavior if it is caused
genetically, since the genetic differences among human groups are small. The approach taken by most
evolutionary psychologists is to predict the outcome of a behavior in a particular situation based on

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evolutionary theory and then to make observations, or conduct experiments, to determine whether the
results match the theory. It is important to recognize that these types of studies are not strong evidence
that a behavior is adaptive, since they lack information that the behavior is in some part genetic and not
entirely cultural (Endler, 1986). Demonstrating that a trait, especially in humans, is naturally selected is
extraordinarily difficult; perhaps for this reason, some evolutionary psychologists are content to assume
the behaviors they study have genetic determinants (Confer et al., 2010).

One other drawback of evolutionary psychology is that the traits that we possess now evolved under
environmental and social conditions far back in human history, and we have a poor understanding of what
these conditions were. This makes predictions about what is adaptive for a behavior difficult. Behavioral
traits need not be adaptive under current conditions, only under the conditions of the past when they
evolved, about which we can only hypothesize.

There are many areas of human behavior for which evolution can make predictions. Examples include
memory, mate choice, relationships between kin, friendship and cooperation, parenting, social
organization, and status (Confer et al., 2010).

Evolutionary psychologists have had success in finding experimental correspondence between
observations and expectations. In one example, in a study of mate preference differences between men and
women that spanned 37 cultures, Buss (1989) found that women valued earning potential factors greater
than men, and men valued potential reproductive factors (youth and attractiveness) greater than women in
their prospective mates. In general, the predictions were in line with the predictions of evolution, although
there were deviations in some cultures.

SENSATION AND PERCEPTION

Scientists interested in both physiological aspects of sensory systems as well as in the psychological
experience of sensory information work within the area of sensation and perception (Figure 1.11). As
such, sensation and perception research is also quite interdisciplinary. Imagine walking between buildings
as you move from one class to another. You are inundated with sights, sounds, touch sensations, and
smells. You also experience the temperature of the air around you and maintain your balance as you make
your way. These are all factors of interest to someone working in the domain of sensation and perception.

Figure 1.11 When you look at this image, you may see a duck or a rabbit. The sensory information remains the
same, but your perception can vary dramatically.

As described in a later chapter that focuses on the results of studies in sensation and perception, our
experience of our world is not as simple as the sum total of all of the sensory information (or sensations)
together. Rather, our experience (or perception) is complex and is influenced by where we focus our
attention, our previous experiences, and even our cultural backgrounds.

COGNITIVE PSYCHOLOGY

As mentioned in the previous section, the cognitive revolution created an impetus for psychologists to
focus their attention on better understanding the mind and mental processes that underlie behavior. Thus,
cognitive psychology is the area of psychology that focuses on studying cognitions, or thoughts, and

Chapter 1 | Introduction to Psychology 21

their relationship to our experiences and our actions. Like biological psychology, cognitive psychology is
broad in its scope and often involves collaborations among people from a diverse range of disciplinary
backgrounds. This has led some to coin the term cognitive science to describe the interdisciplinary nature
of this area of research (Miller, 2003).

Cognitive psychologists have research interests that span a spectrum of topics, ranging from attention to
problem solving to language to memory. The approaches used in studying these topics are equally diverse.
Given such diversity, cognitive psychology is not captured in one chapter of this text per se; rather, various
concepts related to cognitive psychology will be covered in relevant portions of the chapters in this text
on sensation and perception, thinking and intelligence, memory, lifespan development, social psychology,
and therapy.

DEVELOPMENTAL PSYCHOLOGY

Developmental psychology is the scientific study of development across a lifespan. Developmental
psychologists are interested in processes related to physical maturation. However, their focus is not limited
to the physical changes associated with aging, as they also focus on changes in cognitive skills, moral
reasoning, social behavior, and other psychological attributes.

Early developmental psychologists focused primarily on changes that occurred through reaching
adulthood, providing enormous insight into the differences in physical, cognitive, and social capacities
that exist between very young children and adults. For instance, research by Jean Piaget (Figure 1.12)
demonstrated that very young children do not demonstrate object permanence. Object permanence refers
to the understanding that physical things continue to exist, even if they are hidden from us. If you were to
show an adult a toy, and then hide it behind a curtain, the adult knows that the toy still exists. However,
very young infants act as if a hidden object no longer exists. The age at which object permanence is
achieved is somewhat controversial (Munakata, McClelland, Johnson, and Siegler, 1997).

Figure 1.12 Jean Piaget is famous for his theories regarding changes in cognitive ability that occur as we move from
infancy to adulthood.

While Piaget was focused on cognitive changes during infancy and childhood as we move to adulthood,
there is an increasing interest in extending research into the changes that occur much later in life. This
may be reflective of changing population demographics of developed nations as a whole. As more and
more people live longer lives, the number of people of advanced age will continue to increase. Indeed,
it is estimated that there were just over 40 million people aged 65 or older living in the United States
in 2010. However, by 2020, this number is expected to increase to about 55 million. By the year 2050, it
is estimated that nearly 90 million people in this country will be 65 or older (Department of Health and

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Human Services, n.d.).

PERSONALITY PSYCHOLOGY

Personality psychology focuses on patterns of thoughts and behaviors that make each individual unique.
Several individuals (e.g., Freud and Maslow) that we have already discussed in our historical overview of
psychology, and the American psychologist Gordon Allport, contributed to early theories of personality.
These early theorists attempted to explain how an individual’s personality develops from his or her
given perspective. For example, Freud proposed that personality arose as conflicts between the conscious
and unconscious parts of the mind were carried out over the lifespan. Specifically, Freud theorized that
an individual went through various psychosexual stages of development. According to Freud, adult
personality would result from the resolution of various conflicts that centered on the migration of
erogenous (or sexual pleasure-producing) zones from the oral (mouth) to the anus to the phallus to the
genitals. Like many of Freud’s theories, this particular idea was controversial and did not lend itself to
experimental tests (Person, 1980).

More recently, the study of personality has taken on a more quantitative approach. Rather than explaining
how personality arises, research is focused on identifying personality traits, measuring these traits, and
determining how these traits interact in a particular context to determine how a person will behave in
any given situation. Personality traits are relatively consistent patterns of thought and behavior, and
many have proposed that five trait dimensions are sufficient to capture the variations in personality seen
across individuals. These five dimensions are known as the “Big Five” or the Five Factor model, and
include dimensions of conscientiousness, agreeableness, neuroticism, openness, and extraversion (Figure
1.13). Each of these traits has been demonstrated to be relatively stable over the lifespan (e.g., Rantanen,
Metsäpelto, Feldt, Pulkinnen, and Kokko, 2007; Soldz & Vaillant, 1999; McCrae & Costa, 2008) and is
influenced by genetics (e.g., Jang, Livesly, and Vernon, 1996).

Chapter 1 | Introduction to Psychology 23

Figure 1.13 Each of the dimensions of the Five Factor model is shown in this figure. The provided description would
describe someone who scored highly on that given dimension. Someone with a lower score on a given dimension
could be described in opposite terms.

SOCIAL PSYCHOLOGY

Social psychology focuses on how we interact with and relate to others. Social psychologists conduct
research on a wide variety of topics that include differences in how we explain our own behavior versus
how we explain the behaviors of others, prejudice, and attraction, and how we resolve interpersonal
conflicts. Social psychologists have also sought to determine how being among other people changes our
own behavior and patterns of thinking.

There are many interesting examples of social psychological research, and you will read about many of
these in a later chapter of this textbook. Until then, you will be introduced to one of the most controversial
psychological studies ever conducted. Stanley Milgram was an American social psychologist who is
most famous for research that he conducted on obedience. After the holocaust, in 1961, a Nazi war
criminal, Adolf Eichmann, who was accused of committing mass atrocities, was put on trial. Many people
wondered how German soldiers were capable of torturing prisoners in concentration camps, and they
were unsatisfied with the excuses given by soldiers that they were simply following orders. At the
time, most psychologists agreed that few people would be willing to inflict such extraordinary pain and
suffering, simply because they were obeying orders. Milgram decided to conduct research to determine
whether or not this was true (Figure 1.14). As you will read later in the text, Milgram found that nearly
two-thirds of his participants were willing to deliver what they believed to be lethal shocks to another

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person, simply because they were instructed to do so by an authority figure (in this case, a man dressed in
a lab coat). This was in spite of the fact that participants received payment for simply showing up for the
research study and could have chosen not to inflict pain or more serious consequences on another person
by withdrawing from the study. No one was actually hurt or harmed in any way, Milgram’s experiment
was a clever ruse that took advantage of research confederates, those who pretend to be participants in
a research study who are actually working for the researcher and have clear, specific directions on how
to behave during the research study (Hock, 2009). Milgram’s and others’ studies that involved deception
and potential emotional harm to study participants catalyzed the development of ethical guidelines for
conducting psychological research that discourage the use of deception of research subjects, unless it can
be argued not to cause harm and, in general, requiring informed consent of participants.

Figure 1.14 Stanley Milgram’s research demonstrated just how far people will go in obeying orders from an authority
figure. This advertisement was used to recruit subjects for his research.

INDUSTRIAL-ORGANIZATIONAL PSYCHOLOGY

Industrial-Organizational psychology (I-O psychology) is a subfield of psychology that applies
psychological theories, principles, and research findings in industrial and organizational settings. I-O
psychologists are often involved in issues related to personnel management, organizational structure,
and workplace environment. Businesses often seek the aid of I-O psychologists to make the best hiring
decisions as well as to create an environment that results in high levels of employee productivity and
efficiency. In addition to its applied nature, I-O psychology also involves conducting scientific research on
behavior within I-O settings (Riggio, 2013).

Chapter 1 | Introduction to Psychology 25

HEALTH PSYCHOLOGY

Health psychology focuses on how health is affected by the interaction of biological, psychological, and
sociocultural factors. This particular approach is known as the biopsychosocial model (Figure 1.15).
Health psychologists are interested in helping individuals achieve better health through public policy,
education, intervention, and research. Health psychologists might conduct research that explores the
relationship between one’s genetic makeup, patterns of behavior, relationships, psychological stress,
and health. They may research effective ways to motivate people to address patterns of behavior that
contribute to poorer health (MacDonald, 2013).

Figure 1.15 The biopsychosocial model suggests that health/illness is determined by an interaction of these three
factors.

SPORT AND EXERCISE PSYCHOLOGY

Researchers in sport and exercise psychology study the psychological aspects of sport performance,
including motivation and performance anxiety, and the effects of sport on mental and emotional
wellbeing. Research is also conducted on similar topics as they relate to physical exercise in general. The
discipline also includes topics that are broader than sport and exercise but that are related to interactions
between mental and physical performance under demanding conditions, such as fire fighting, military
operations, artistic performance, and surgery.

CLINICAL PSYCHOLOGY

Clinical psychology is the area of psychology that focuses on the diagnosis and treatment of psychological
disorders and other problematic patterns of behavior. As such, it is generally considered to be a more
applied area within psychology; however, some clinicians are also actively engaged in scientific research.
Counseling psychology is a similar discipline that focuses on emotional, social, vocational, and health-
related outcomes in individuals who are considered psychologically healthy.

As mentioned earlier, both Freud and Rogers provided perspectives that have been influential in shaping
how clinicians interact with people seeking psychotherapy. While aspects of the psychoanalytic theory are
still found among some of today’s therapists who are trained from a psychodynamic perspective, Roger’s
ideas about client-centered therapy have been especially influential in shaping how many clinicians
operate. Furthermore, both behaviorism and the cognitive revolution have shaped clinical practice in the
forms of behavioral therapy, cognitive therapy, and cognitive-behavioral therapy (Figure 1.16). Issues

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related to the diagnosis and treatment of psychological disorders and problematic patterns of behavior will
be discussed in detail in later chapters of this textbook.

Figure 1.16 Cognitive-behavioral therapists take cognitive processes and behaviors into account when providing
psychotherapy. This is one of several strategies that may be used by practicing clinical psychologists.

By far, this is the area of psychology that receives the most attention in popular media, and many people
mistakenly assume that all psychology is clinical psychology.

FORENSIC PSYCHOLOGY

Forensic psychology is a branch of psychology that deals questions of psychology as they arise in the
context of the justice system. For example, forensic psychologists (and forensic psychiatrists) will assess
a person’s competency to stand trial, assess the state of mind of a defendant, act as consultants on
child custody cases, consult on sentencing and treatment recommendations, and advise on issues such as
eyewitness testimony and children’s testimony (American Board of Forensic Psychology, 2014). In these
capacities, they will typically act as expert witnesses, called by either side in a court case to provide their
research- or experience-based opinions. As expert witnesses, forensic psychologists must have a good
understanding of the law and provide information in the context of the legal system rather than just within
the realm of psychology. Forensic psychologists are also used in the jury selection process and witness
preparation. They may also be involved in providing psychological treatment within the criminal justice
system. Criminal profilers are a relatively small proportion of psychologists that act as consultants to law
enforcement.

1.4 Careers in Psychology

Learning Objectives

By the end of this section, you will be able to:
• Understand educational requirements for careers in academic settings
• Understand the demands of a career in an academic setting
• Understand career options outside of academic settings

Psychologists can work in many different places doing many different things. In general, anyone wishing
to continue a career in psychology at a 4-year institution of higher education will have to earn a doctoral
degree in psychology for some specialties and at least a master’s degree for others. In most areas of
psychology, this means earning a PhD in a relevant area of psychology. Literally, PhD refers to a doctor
of philosophy degree, but here, philosophy does not refer to the field of philosophy per se. Rather,

Chapter 1 | Introduction to Psychology 27

philosophy in this context refers to many different disciplinary perspectives that would be housed in a
traditional college of liberal arts and sciences.

The requirements to earn a PhD vary from country to country and even from school to school, but usually,
individuals earning this degree must complete a dissertation. A dissertation is essentially a long research
paper or bundled published articles describing research that was conducted as a part of the candidate’s
doctoral training. In the United States, a dissertation generally has to be defended before a committee of
expert reviewers before the degree is conferred (Figure 1.17).

Figure 1.17 Doctoral degrees are generally conferred in formal ceremonies involving special attire and rites. (credit:
Public Affairs Office Fort Wainwright)

Once someone earns a PhD, they may seek a faculty appointment at a college or university. Being on the
faculty of a college or university often involves dividing time between teaching, research, and service to
the institution and profession. The amount of time spent on each of these primary responsibilities varies
dramatically from school to school, and it is not uncommon for faculty to move from place to place in
search of the best personal fit among various academic environments. The previous section detailed some
of the major areas that are commonly represented in psychology departments around the country; thus,
depending on the training received, an individual could be anything from a biological psychologist to a
clinical psychologist in an academic setting (Figure 1.18).

Figure 1.18 Individuals earning a PhD in psychology have a range of employment options.

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Use this interactive tool and explore different careers in psychology based on degree levels
(http://openstax.org/l/degreecareer) to learn more.

OTHER CAREERS IN ACADEMIC SETTINGS

Often times, schools offer more courses in psychology than their full-time faculty can teach. In these cases,
it is not uncommon to bring in an adjunct faculty member or instructor. Adjunct faculty members and
instructors usually have an advanced degree in psychology, but they often have primary careers outside
of academia and serve in this role as a secondary job. Alternatively, they may not hold the doctoral
degree required by most 4-year institutions and use these opportunities to gain experience in teaching.
Furthermore, many 2-year colleges and schools need faculty to teach their courses in psychology. In
general, many of the people who pursue careers at these institutions have master’s degrees in psychology,
although some PhDs make careers at these institutions as well.

Some people earning PhDs may enjoy research in an academic setting. However, they may not be
interested in teaching. These individuals might take on faculty positions that are exclusively devoted
to conducting research. This type of position would be more likely an option at large, research-focused
universities.

In some areas in psychology, it is common for individuals who have recently earned their PhD to seek out
positions in postdoctoral training programs that are available before going on to serve as faculty. In most
cases, young scientists will complete one or two postdoctoral programs before applying for a full-time
faculty position. Postdoctoral training programs allow young scientists to further develop their research
programs and broaden their research skills under the supervision of other professionals in the field.

CAREER OPTIONS OUTSIDE OF ACADEMIC SETTINGS

Individuals who wish to become practicing clinical psychologists have another option for earning a
doctoral degree, which is known as a PsyD. A PsyD is a doctor of psychology degree that is increasingly
popular among individuals interested in pursuing careers in clinical psychology. PsyD programs generally
place less emphasis on research-oriented skills and focus more on application of psychological principles
in the clinical context (Norcorss & Castle, 2002).

Regardless of whether earning a PhD or PsyD, in most states, an individual wishing to practice as
a licensed clinical or counseling psychologist may complete postdoctoral work under the supervision
of a licensed psychologist. Within the last few years, however, several states have begun to remove
this requirement, which would allow people to get an earlier start in their careers (Munsey, 2009).
After an individual has met the state requirements, their credentials are evaluated to determine whether
they can sit for the licensure exam. Only individuals that pass this exam can call themselves licensed
clinical or counseling psychologists (Norcross, n.d.). Licensed clinical or counseling psychologists can
then work in a number of settings, ranging from private clinical practice to hospital settings. It should
be noted that clinical psychologists and psychiatrists do different things and receive different types of
education. While both can conduct therapy and counseling, clinical psychologists have a PhD or a PsyD,
whereas psychiatrists have a doctor of medicine degree (MD). As such, licensed clinical psychologists can
administer and interpret psychological tests, while psychiatrists can prescribe medications.

Individuals earning a PhD can work in a variety of settings, depending on their areas of specialization.
For example, someone trained as a biopsychologist might work in a pharmaceutical company to help test
the efficacy of a new drug. Someone with a clinical background might become a forensic psychologist and
work within the legal system to make recommendations during criminal trials and parole hearings, or

LINK TO LEARNING

Chapter 1 | Introduction to Psychology 29

serve as an expert in a court case.

While earning a doctoral degree in psychology is a lengthy process, usually taking between 5–6 years of
graduate study (DeAngelis, 2010), there are a number of careers that can be attained with a master’s degree
in psychology. People who wish to provide psychotherapy can become licensed to serve as various types
of professional counselors (Hoffman, 2012). Relevant master’s degrees are also sufficient for individuals
seeking careers as school psychologists (National Association of School Psychologists, n.d.), in some
capacities related to sport psychology (American Psychological Association, 2014), or as consultants in
various industrial settings (Landers, 2011, June 14). Undergraduate coursework in psychology may be
applicable to other careers such as psychiatric social work or psychiatric nursing, where assessments and
therapy may be a part of the job.

As mentioned in the opening section of this chapter, an undergraduate education in psychology is
associated with a knowledge base and skill set that many employers find quite attractive. It should come as
no surprise, then, that individuals earning bachelor’s degrees in psychology find themselves in a number
of different careers, as shown in Table 1.1. Examples of a few such careers can involve serving as case
managers, working in sales, working in human resource departments, and teaching in high schools. The
rapidly growing realm of healthcare professions is another field in which an education in psychology is
helpful and sometimes required. For example, the Medical College Admission Test (MCAT) exam that
people must take to be admitted to medical school now includes a section on the psychological foundations
of behavior.

Top Occupations Employing Graduates with a BA in Psychology (Fogg, Harrington, Harrington,
& Shatkin, 2012)

Ranking Occupation

1 Mid- and top-level management (executive, administrator)

2 Sales

3 Social work

4 Other management positions

5 Human resources (personnel, training)

6 Other administrative positions

7 Insurance, real estate, business

8 Marketing and sales

9 Healthcare (nurse, pharmacist, therapist)

10 Finance (accountant, auditor)

Table 1.1

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The APA provides career information (http://openstax.org/l/careers) about various areas of
psychology.

LINK TO LEARNING

Chapter 1 | Introduction to Psychology 31

American Psychological Association (APA)

behaviorism

biopsychology

biopsychosocial model

clinical psychology

cognitive psychology

counseling psychology

developmental psychology

dissertation

empirical method

forensic psychology

functionalism

humanism

introspection

ology

personality psychology

personality trait

PhD

postdoctoral training program

psychoanalytic theory

psychology

PsyD

Key Terms

professional organization representing psychologists in the
United States

focus on observing and controlling behavior

study of how biology influences behavior

perspective that asserts that biology, psychology, and social factors interact to
determine an individual’s health

area of psychology that focuses on the diagnosis and treatment of psychological
disorders and other problematic patterns of behavior

study of cognitions, or thoughts, and their relationship to experiences and actions

area of psychology that focuses on improving emotional, social, vocational, and
other aspects of the lives of psychologically healthy individuals

scientific study of development across a lifespan

long research paper about research that was conducted as a part of the candidate’s doctoral
training

method for acquiring knowledge based on observation, including experimentation,
rather than a method based only on forms of logical argument or previous authorities

area of psychology that applies the science and practice of psychology to issues
within and related to the justice system

focused on how mental activities helped an organism adapt to its environment

perspective within psychology that emphasizes the potential for good that is innate to all
humans

process by which someone examines their own conscious experience in an attempt to
break it into its component parts

suffix that denotes “scientific study of”

study of patterns of thoughts and behaviors that make each individual unique

consistent pattern of thought and behavior

(doctor of philosophy) doctoral degree conferred in many disciplinary perspectives housed in a
traditional college of liberal arts and sciences

allows programs and broaden their research skills under the supervision
of other professionals in the field

focus on the role of the unconscious in affecting conscious behavior

scientific study of the mind and behavior

(doctor of psychology) doctoral degree that places less emphasis on research-oriented skills and
focuses more on application of psychological principles in the clinical context

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sport and exercise psychology

structuralism

area of psychology that focuses on the interactions between mental and
emotional factors and physical performance in sports, exercise, and other activities

understanding the conscious experience through introspection

Summary

1.1 What Is Psychology?
Psychology is defined as the scientific study of mind and behavior. Students of psychology develop critical
thinking skills, become familiar with the scientific method, and recognize the complexity of behavior.

1.2 History of Psychology
Before the time of Wundt and James, questions about the mind were considered by philosophers.
However, both Wundt and James helped create psychology as a distinct scientific discipline. Wundt was a
structuralist, which meant he believed that our cognitive experience was best understood by breaking that
experience into its component parts. He thought this was best accomplished by introspection.

William James was the first American psychologist, and he was a proponent of functionalism. This
particular perspective focused on how mental activities served as adaptive responses to an organism’s
environment. Like Wundt, James also relied on introspection; however, his research approach also
incorporated more objective measures as well.

Sigmund Freud believed that understanding the unconscious mind was absolutely critical to understand
conscious behavior. This was especially true for individuals that he saw who suffered from various
hysterias and neuroses. Freud relied on dream analysis, slips of the tongue, and free association as means
to access the unconscious. Psychoanalytic theory remained a dominant force in clinical psychology for
several decades.

Gestalt psychology was very influential in Europe. Gestalt psychology takes a holistic view of an
individual and his experiences. As the Nazis came to power in Germany, Wertheimer, Koffka, and Köhler
immigrated to the United States. Although they left their laboratories and their research behind, they did
introduce America to Gestalt ideas. Some of the principles of Gestalt psychology are still very influential
in the study of sensation and perception.

One of the most influential schools of thought within psychology’s history was behaviorism. Behaviorism
focused on making psychology an objective science by studying overt behavior and deemphasizing the
importance of unobservable mental processes. John Watson is often considered the father of behaviorism,
and B. F. Skinner’s contributions to our understanding of principles of operant conditioning cannot be
underestimated.

As behaviorism and psychoanalytic theory took hold of so many aspects of psychology, some began to
become dissatisfied with psychology’s picture of human nature. Thus, a humanistic movement within
psychology began to take hold. Humanism focuses on the potential of all people for good. Both Maslow
and Rogers were influential in shaping humanistic psychology.

During the 1950s, the landscape of psychology began to change. A science of behavior began to shift back
to its roots of focus on mental processes. The emergence of neuroscience and computer science aided this
transition. Ultimately, the cognitive revolution took hold, and people came to realize that cognition was
crucial to a true appreciation and understanding of behavior.

1.3 Contemporary Psychology
Psychology is a diverse discipline that is made up of several major subdivisions with unique perspectives.
Biological psychology involves the study of the biological bases of behavior. Sensation and perception
refer to the area of psychology that is focused on how information from our sensory modalities is
received, and how this information is transformed into our perceptual experiences of the world around
us. Cognitive psychology is concerned with the relationship that exists between thought and behavior,

Chapter 1 | Introduction to Psychology 33

and developmental psychologists study the physical and cognitive changes that occur throughout one’s
lifespan. Personality psychology focuses on individuals’ unique patterns of behavior, thought, and
emotion. Industrial and organizational psychology, health psychology, sport and exercise psychology,
forensic psychology, and clinical psychology are all considered applied areas of psychology. Industrial
and organizational psychologists apply psychological concepts to I-O settings. Health psychologists look
for ways to help people live healthier lives, and clinical psychology involves the diagnosis and treatment
of psychological disorders and other problematic behavioral patterns. Sport and exercise psychologists
study the interactions between thoughts, emotions, and physical performance in sports, exercise, and other
activities. Forensic psychologists carry out activities related to psychology in association with the justice
system.

1.4 Careers in Psychology
Generally, academic careers in psychology require doctoral degrees. However, there are a number of
nonacademic career options for people who have master’s degrees in psychology. While people with
bachelor’s degrees in psychology have more limited psychology-related career options, the skills acquired
as a function of an undergraduate education in psychology are useful in a variety of work contexts.

Review Questions

1. Which of the following was mentioned as a
skill to which psychology students would be
exposed?

a. critical thinking
b. use of the scientific method
c. critical evaluation of sources of information
d. all of the above

2. Before psychology became a recognized
academic discipline, matters of the mind were
undertaken by those in ________.

a. biology
b. chemistry
c. philosophy
d. physics

3. In the scientific method, a hypothesis is a(n)
________.

a. observation
b. measurement
c. test
d. proposed explanation

4. Based on your reading, which theorist would
have been most likely to agree with this statement:
Perceptual phenomena are best understood as a
combination of their components.

a. William James
b. Max Wertheimer
c. Carl Rogers
d. Noam Chomsky

5. ________ is most well-known for proposing his
hierarchy of needs.

a. Noam Chomsky
b. Carl Rogers
c. Abraham Maslow
d. Sigmund Freud

6. Rogers believed that providing genuineness,
empathy, and ________ in the therapeutic
environment for his clients was critical to their
being able to deal with their problems.

a. structuralism
b. functionalism
c. Gestalt
d. unconditional positive regard

7. The operant conditioning chamber (aka
________ box) is a device used to study the
principles of operant conditioning.

a. Skinner
b. Watson
c. James
d. Koffka

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8. A researcher interested in how changes in the
cells of the hippocampus (a structure in the brain
related to learning and memory) are related to
memory formation would be most likely to
identify as a(n) ________ psychologist.

a. biological
b. health
c. clinical
d. social

9. An individual’s consistent pattern of thought
and behavior is known as a(n) ________.

a. psychosexual stage
b. object permanence
c. personality
d. perception

10. In Milgram’s controversial study on
obedience, nearly ________ of the participants
were willing to administer what appeared to be
lethal electrical shocks to another person because
they were told to do so by an authority figure.

a. 1/3
b. 2/3
c. 3/4
d. 4/5

11. A researcher interested in what factors make
an employee best suited for a given job would
most likely identify as a(n) ________ psychologist.

a. personality
b. clinical
c. social
d. I-O

12. If someone wanted to become a psychology
professor at a 4-year college, they would probably
need a ________ degree in psychology.

a. bachelor of science
b. bachelor of art
c. master’s
d. PhD

13. The ________ places less emphasis on
research and more emphasis on application of
therapeutic skills.

a. PhD
b. PsyD
c. postdoctoral training program
d. dissertation

14. Which of the following degrees would be the
minimum required to teach psychology courses in
high school?

a. PhD
b. PsyD
c. master’s degree
d. bachelor’s degree

15. One would need at least a(n) ________ degree
to serve as a school psychologist.

a. associate’s
b. bachelor’s
c. master’s
d. doctoral

Critical Thinking Questions

16. Why do you think psychology courses like this one are often requirements of so many different
programs of study?

17. Why do you think many people might be skeptical about psychology being a science?

18. How did the object of study in psychology change over the history of the field since the 19th century?

19. In part, what aspect of psychology was the behaviorist approach to psychology a reaction to?

20. Given the incredible diversity among the various areas of psychology that were described in this
section, how do they all fit together?

21. What are the potential ethical concerns associated with Milgram’s research on obedience?

Chapter 1 | Introduction to Psychology 35

22. Why is an undergraduate education in psychology so helpful in a number of different lines of work?

23. Other than a potentially greater salary, what would be the reasons an individual would continue on
to get a graduate degree in psychology?

Personal Application Questions

24. Why are you taking this course? What do you hope to learn about during this course?

25. Freud is probably one of the most well-known historical figures in psychology. Where have you
encountered references to Freud or his ideas about the role that the unconscious mind plays in determining
conscious behavior?

26. Now that you’ve been briefly introduced to some of the major areas within psychology, which are you
most interested in learning more about? Why?

27. Which of the career options in the field of psychology is most appealing to you?

36 Chapter 1 | Introduction to Psychology

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Chapter 2

Psychological Research

Figure 2.1 How does television content impact children’s behavior? (credit: modification of work by
“antisocialtory”/Flickr)

Chapter Outline

2.1 Why Is Research Important?

2.2 Approaches to Research

2.3 Analyzing Findings

2.4 Ethics

Introduction

Have you ever wondered whether the violence you see on television affects your behavior? Are you more
likely to behave aggressively in real life after watching people behave violently in dramatic situations on
the screen? Or, could seeing fictional violence actually get aggression out of your system, causing you to be
more peaceful? How are children influenced by the media they are exposed to? A psychologist interested
in the relationship between behavior and exposure to violent images might ask these very questions.

Since ancient times, humans have been concerned about the effects of new technologies on our behaviors
and thinking processes. The Greek philosopher Socrates, for example, worried that writing—a new
technology at that time—would diminish people’s ability to remember because they could rely on written
records rather than committing information to memory. In our world of rapidly changing technologies,
questions about their effects on our daily lives and their resulting long-term impacts continue to emerge.
In addition to the impact of screen time (on smartphones, tablets, computers, and gaming), technology is
emerging in our vehicles (such as GPS and smart cars) and residences (with devices like Alexa or Google
Home and doorbell cameras). As these technologies become integrated into our lives, we are faced with
questions about their positive and negative impacts. Many of us find ourselves with a strong opinion on
these issues, only to find the person next to us bristling with the opposite view.

Chapter 2 | Psychological Research 37

How can we go about finding answers that are supported not by mere opinion, but by evidence that we
can all agree on? The findings of psychological research can help us navigate issues like this.

2.1 Why Is Research Important?

Learning Objectives

By the end of this section, you will be able to:
• Explain how scientific research addresses questions about behavior
• Discuss how scientific research guides public policy
• Appreciate how scientific research can be important in making personal decisions

Scientific research is a critical tool for successfully navigating our complex world. Without it, we would be
forced to rely solely on intuition, other people’s authority, and blind luck. While many of us feel confident
in our abilities to decipher and interact with the world around us, history is filled with examples of how
very wrong we can be when we fail to recognize the need for evidence in supporting claims. At various
times in history, we would have been certain that the sun revolved around a flat earth, that the earth’s
continents did not move, and that mental illness was caused by possession (Figure 2.2). It is through
systematic scientific research that we divest ourselves of our preconceived notions and superstitions and
gain an objective understanding of ourselves and our world.

Figure 2.2 Some of our ancestors, across the world and over the centuries, believed that trephination—the practice
of making a hole in the skull, as shown here—allowed evil spirits to leave the body, thus curing mental illness and
other disorders. (credit: “taiproject”/Flickr)

The goal of all scientists is to better understand the world around them. Psychologists focus their attention
on understanding behavior, as well as the cognitive (mental) and physiological (body) processes that
underlie behavior. In contrast to other methods that people use to understand the behavior of others,
such as intuition and personal experience, the hallmark of scientific research is that there is evidence to
support a claim. Scientific knowledge is empirical: It is grounded in objective, tangible evidence that can
be observed time and time again, regardless of who is observing.

While behavior is observable, the mind is not. If someone is crying, we can see behavior. However, the
reason for the behavior is more difficult to determine. Is the person crying due to being sad, in pain,
or happy? Sometimes we can learn the reason for someone’s behavior by simply asking a question, like
“Why are you crying?” However, there are situations in which an individual is either uncomfortable or
unwilling to answer the question honestly, or is incapable of answering. For example, infants would not
be able to explain why they are crying. In such circumstances, the psychologist must be creative in finding
ways to better understand behavior. This chapter explores how scientific knowledge is generated, and how

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important that knowledge is in forming decisions in our personal lives and in the public domain.

USE OF RESEARCH INFORMATION

Trying to determine which theories are and are not accepted by the scientific community can be difficult,
especially in an area of research as broad as psychology. More than ever before, we have an incredible
amount of information at our fingertips, and a simple internet search on any given research topic might
result in a number of contradictory studies. In these cases, we are witnessing the scientific community
going through the process of reaching a consensus, and it could be quite some time before a consensus
emerges. For example, the explosion in our use of technology has led researchers to question whether
this ultimately helps or hinders us. The use and implementation of technology in educational settings has
become widespread over the last few decades. Researchers are coming to different conclusions regarding
the use of technology. To illustrate this point, a study investigating a smartphone app targeting surgery
residents (graduate students in surgery training) found that the use of this app can increase student
engagement and raise test scores (Shaw & Tan, 2015). Conversely, another study found that the use of
technology in undergraduate student populations had negative impacts on sleep, communication, and
time management skills (Massimini & Peterson, 2009). Until sufficient amounts of research have been
conducted, there will be no clear consensus on the effects that technology has on a student’s acquisition of
knowledge, study skills, and mental health.

In the meantime, we should strive to think critically about the information we encounter by exercising a
degree of healthy skepticism. When someone makes a claim, we should examine the claim from a number
of different perspectives: what is the expertise of the person making the claim, what might they gain if the
claim is valid, does the claim seem justified given the evidence, and what do other researchers think of
the claim? This is especially important when we consider how much information in advertising campaigns
and on the internet claims to be based on “scientific evidence” when in actuality it is a belief or perspective
of just a few individuals trying to sell a product or draw attention to their perspectives.

We should be informed consumers of the information made available to us because decisions based on
this information have significant consequences. One such consequence can be seen in politics and public
policy. Imagine that you have been elected as the governor of your state. One of your responsibilities is
to manage the state budget and determine how to best spend your constituents’ tax dollars. As the new
governor, you need to decide whether to continue funding early intervention programs. These programs
are designed to help children who come from low-income backgrounds, have special needs, or face
other disadvantages. These programs may involve providing a wide variety of services to maximize the
children’s development and position them for optimal levels of success in school and later in life (Blann,
2005). While such programs sound appealing, you would want to be sure that they also proved effective
before investing additional money in these programs. Fortunately, psychologists and other scientists have
conducted vast amounts of research on such programs and, in general, the programs are found to be
effective (Neil & Christensen, 2009; Peters-Scheffer, Didden, Korzilius, & Sturmey, 2011). While not all
programs are equally effective, and the short-term effects of many such programs are more pronounced,
there is reason to believe that many of these programs produce long-term benefits for participants (Barnett,
2011). If you are committed to being a good steward of taxpayer money, you would want to look at
research. Which programs are most effective? What characteristics of these programs make them effective?
Which programs promote the best outcomes? After examining the research, you would be best equipped
to make decisions about which programs to fund.

Chapter 2 | Psychological Research 39

Watch this video about early childhood program effectiveness (http://openstax.org/l/programeffect)
to learn how scientists evaluate effectiveness and how best to invest money into programs that are most
effective.

Ultimately, it is not just politicians who can benefit from using research in guiding their decisions. We all
might look to research from time to time when making decisions in our lives. Imagine you just found out
that a close friend has breast cancer or that one of your young relatives has recently been diagnosed with
autism. In either case, you want to know which treatment options are most successful with the fewest side
effects. How would you find that out? You would probably talk with your doctor and personally review
the research that has been done on various treatment options—always with a critical eye to ensure that
you are as informed as possible.

In the end, research is what makes the difference between facts and opinions. Facts are observable realities,
and opinions are personal judgments, conclusions, or attitudes that may or may not be accurate. In the
scientific community, facts can be established only using evidence collected through empirical research.

NOTABLE RESEARCHERS

Psychological research has a long history involving important figures from diverse backgrounds. While
the introductory chapter discussed several researchers who made significant contributions to the
discipline, there are many more individuals who deserve attention in considering how psychology has
advanced as a science through their work (Figure 2.3). For instance, Margaret Floy Washburn (1871–1939)
was the first woman to earn a PhD in psychology. Her research focused on animal behavior and cognition
(Margaret Floy Washburn, PhD, n.d.). Mary Whiton Calkins (1863–1930) was a preeminent first-generation
American psychologist who opposed the behaviorist movement, conducted significant research into
memory, and established one of the earliest experimental psychology labs in the United States (Mary
Whiton Calkins, n.d.).

Francis Sumner (1895–1954) was the first African American to receive a PhD in psychology in 1920. His
dissertation focused on issues related to psychoanalysis. Sumner also had research interests in racial
bias and educational justice. Sumner was one of the founders of Howard University’s department of
psychology, and because of his accomplishments, he is sometimes referred to as the “Father of Black
Psychology.” Thirteen years later, Inez Beverly Prosser (1895–1934) became the first African American
woman to receive a PhD in psychology. Prosser’s research highlighted issues related to education in
segregated versus integrated schools, and ultimately, her work was very influential in the hallmark
Brown v. Board of Education Supreme Court ruling that segregation of public schools was unconstitutional
(Ethnicity and Health in America Series: Featured Psychologists, n.d.).

LINK TO LEARNING

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Figure 2.3 (a) Margaret Floy Washburn was the first woman to earn a doctorate degree in psychology. (b) The
outcome of Brown v. Board of Education was influenced by the research of psychologist Inez Beverly Prosser, who
was the first African American woman to earn a PhD in psychology.

Although the establishment of psychology’s scientific roots occurred first in Europe and the United States,
it did not take much time until researchers from around the world began to establish their own laboratories
and research programs. For example, some of the first experimental psychology laboratories in South
America were founded by Horatio Piñero (1869–1919) at two institutions in Buenos Aires, Argentina
(Godoy & Brussino, 2010). In India, Gunamudian David Boaz (1908–1965) and Narendra Nath Sen Gupta
(1889–1944) established the first independent departments of psychology at the University of Madras
and the University of Calcutta, respectively. These developments provided an opportunity for Indian
researchers to make important contributions to the field (Gunamudian David Boaz, n.d.; Narendra Nath
Sen Gupta, n.d.).

When the American Psychological Association (APA) was first founded in 1892, all of the members were
white males (Women and Minorities in Psychology, n.d.). However, by 1905, Mary Whiton Calkins was
elected as the first female president of the APA, and by 1946, nearly one-quarter of American psychologists
were female. Psychology became a popular degree option for students enrolled in the nation’s historically
black higher education institutions, increasing the number of black Americans who went on to become
psychologists. Given demographic shifts occurring in the United States and increased access to higher
educational opportunities among historically underrepresented populations, there is reason to hope that
the diversity of the field will increasingly match the larger population, and that the research contributions
made by the psychologists of the future will better serve people of all backgrounds (Women and Minorities
in Psychology, n.d.).

THE PROCESS OF SCIENTIFIC RESEARCH

Scientific knowledge is advanced through a process known as the scientific method. Basically, ideas (in the
form of theories and hypotheses) are tested against the real world (in the form of empirical observations),
and those empirical observations lead to more ideas that are tested against the real world, and so on. In this
sense, the scientific process is circular. The types of reasoning within the circle are called deductive and
inductive. In deductive reasoning, ideas are tested in the real world; in inductive reasoning, real-world
observations lead to new ideas (Figure 2.4). These processes are inseparable, like inhaling and exhaling,
but different research approaches place different emphasis on the deductive and inductive aspects.

Chapter 2 | Psychological Research 41

Figure 2.4 Psychological research relies on both inductive and deductive reasoning.

In the scientific context, deductive reasoning begins with a generalization—one hypothesis—that is then
used to reach logical conclusions about the real world. If the hypothesis is correct, then the logical
conclusions reached through deductive reasoning should also be correct. A deductive reasoning argument
might go something like this: All living things require energy to survive (this would be your hypothesis).
Ducks are living things. Therefore, ducks require energy to survive (logical conclusion). In this example,
the hypothesis is correct; therefore, the conclusion is correct as well. Sometimes, however, an incorrect
hypothesis may lead to a logical but incorrect conclusion. Consider this argument: all ducks are born with
the ability to see. Quackers is a duck. Therefore, Quackers was born with the ability to see. Scientists
use deductive reasoning to empirically test their hypotheses. Returning to the example of the ducks,
researchers might design a study to test the hypothesis that if all living things require energy to survive,
then ducks will be found to require energy to survive.

Deductive reasoning starts with a generalization that is tested against real-world observations; however,
inductive reasoning moves in the opposite direction. Inductive reasoning uses empirical observations to
construct broad generalizations. Unlike deductive reasoning, conclusions drawn from inductive reasoning
may or may not be correct, regardless of the observations on which they are based. For instance, you may
notice that your favorite fruits—apples, bananas, and oranges—all grow on trees; therefore, you assume
that all fruit must grow on trees. This would be an example of inductive reasoning, and, clearly, the
existence of strawberries, blueberries, and kiwi demonstrate that this generalization is not correct despite
it being based on a number of direct observations. Scientists use inductive reasoning to formulate theories,
which in turn generate hypotheses that are tested with deductive reasoning. In the end, science involves
both deductive and inductive processes.

For example, case studies, which you will read about in the next section, are heavily weighted on the
side of empirical observations. Thus, case studies are closely associated with inductive processes as
researchers gather massive amounts of observations and seek interesting patterns (new ideas) in the data.
Experimental research, on the other hand, puts great emphasis on deductive reasoning.

We’ve stated that theories and hypotheses are ideas, but what sort of ideas are they, exactly? A theory is a
well-developed set of ideas that propose an explanation for observed phenomena. Theories are repeatedly
checked against the world, but they tend to be too complex to be tested all at once; instead, researchers
create hypotheses to test specific aspects of a theory.

A hypothesis is a testable prediction about how the world will behave if our idea is correct, and it is
often worded as an if-then statement (e.g., if I study all night, I will get a passing grade on the test). The
hypothesis is extremely important because it bridges the gap between the realm of ideas and the real
world. As specific hypotheses are tested, theories are modified and refined to reflect and incorporate the
result of these tests Figure 2.5.

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Figure 2.5 The scientific method involves deriving hypotheses from theories and then testing those hypotheses. If
the results are consistent with the theory, then the theory is supported. If the results are not consistent, then the
theory should be modified and new hypotheses will be generated.

To see how this process works, let’s consider a specific theory and a hypothesis that might be generated
from that theory. As you’ll learn in a later chapter, the James-Lange theory of emotion asserts that
emotional experience relies on the physiological arousal associated with the emotional state. If you walked
out of your home and discovered a very aggressive snake waiting on your doorstep, your heart would
begin to race and your stomach churn. According to the James-Lange theory, these physiological changes
would result in your feeling of fear. A hypothesis that could be derived from this theory might be that a
person who is unaware of the physiological arousal that the sight of the snake elicits will not feel fear.

A scientific hypothesis is also falsifiable, or capable of being shown to be incorrect. Recall from the
introductory chapter that Sigmund Freud had lots of interesting ideas to explain various human behaviors
(Figure 2.6). However, a major criticism of Freud’s theories is that many of his ideas are not falsifiable;
for example, it is impossible to imagine empirical observations that would disprove the existence of the id,
the ego, and the superego—the three elements of personality described in Freud’s theories. Despite this,
Freud’s theories are widely taught in introductory psychology texts because of their historical significance
for personality psychology and psychotherapy, and these remain the root of all modern forms of therapy.

Chapter 2 | Psychological Research 43

Figure 2.6 Many of the specifics of (a) Freud’s theories, such as (b) his division of the mind into id, ego, and
superego, have fallen out of favor in recent decades because they are not falsifiable. In broader strokes, his views set
the stage for much of psychological thinking today, such as the unconscious nature of the majority of psychological
processes.

In contrast, the James-Lange theory does generate falsifiable hypotheses, such as the one described
above. Some individuals who suffer significant injuries to their spinal columns are unable to feel the
bodily changes that often accompany emotional experiences. Therefore, we could test the hypothesis by
determining how emotional experiences differ between individuals who have the ability to detect these
changes in their physiological arousal and those who do not. In fact, this research has been conducted and
while the emotional experiences of people deprived of an awareness of their physiological arousal may be
less intense, they still experience emotion (Chwalisz, Diener, & Gallagher, 1988).

Scientific research’s dependence on falsifiability allows for great confidence in the information that it
produces. Typically, by the time information is accepted by the scientific community, it has been tested
repeatedly.

2.2 Approaches to Research

Learning Objectives

By the end of this section, you will be able to:
• Describe the different research methods used by psychologists
• Discuss the strengths and weaknesses of case studies, naturalistic observation, surveys, and

archival research
• Compare longitudinal and cross-sectional approaches to research
• Compare and contrast correlation and causation

There are many research methods available to psychologists in their efforts to understand, describe,
and explain behavior and the cognitive and biological processes that underlie it. Some methods rely
on observational techniques. Other approaches involve interactions between the researcher and the
individuals who are being studied—ranging from a series of simple questions to extensive, in-depth
interviews—to well-controlled experiments.

Each of these research methods has unique strengths and weaknesses, and each method may only be

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appropriate for certain types of research questions. For example, studies that rely primarily on observation
produce incredible amounts of information, but the ability to apply this information to the larger
population is somewhat limited because of small sample sizes. Survey research, on the other hand,
allows researchers to easily collect data from relatively large samples. While this allows for results to
be generalized to the larger population more easily, the information that can be collected on any given
survey is somewhat limited and subject to problems associated with any type of self-reported data. Some
researchers conduct archival research by using existing records. While this can be a fairly inexpensive
way to collect data that can provide insight into a number of research questions, researchers using this
approach have no control on how or what kind of data was collected. All of the methods described thus
far are correlational in nature. This means that researchers can speak to important relationships that might
exist between two or more variables of interest. However, correlational data cannot be used to make claims
about cause-and-effect relationships.

Correlational research can find a relationship between two variables, but the only way a researcher can
claim that the relationship between the variables is cause and effect is to perform an experiment. In
experimental research, which will be discussed later in this chapter, there is a tremendous amount of
control over variables of interest. While this is a powerful approach, experiments are often conducted in
very artificial settings. This calls into question the validity of experimental findings with regard to how
they would apply in real-world settings. In addition, many of the questions that psychologists would like
to answer cannot be pursued through experimental research because of ethical concerns.

CLINICAL OR CASE STUDIES

In 2011, the New York Times published a feature story on Krista and Tatiana Hogan, Canadian twin girls.
These particular twins are unique because Krista and Tatiana are conjoined twins, connected at the head.
There is evidence that the two girls are connected in a part of the brain called the thalamus, which is
a major sensory relay center. Most incoming sensory information is sent through the thalamus before
reaching higher regions of the cerebral cortex for processing.

Watch this CBC video about Krista’s and Tatiana’s lives (http://openstax.org/l/hogans) to learn more.

The implications of this potential connection mean that it might be possible for one twin to experience the
sensations of the other twin. For instance, if Krista is watching a particularly funny television program,
Tatiana might smile or laugh even if she is not watching the program. This particular possibility has
piqued the interest of many neuroscientists who seek to understand how the brain uses sensory
information.

These twins represent an enormous resource in the study of the brain, and since their condition is very
rare, it is likely that as long as their family agrees, scientists will follow these girls very closely throughout
their lives to gain as much information as possible (Dominus, 2011).

Over time, it has become clear that while Krista and Tatiana share some sensory experiences and motor
control, they remain two distinct individuals, which provides tremendous insight into researchers
interested in the mind and the brain (Egnor, 2017).

In observational research, scientists are conducting a clinical or case study when they focus on one person
or just a few individuals. Indeed, some scientists spend their entire careers studying just 10–20 individuals.
Why would they do this? Obviously, when they focus their attention on a very small number of people,
they can gain a tremendous amount of insight into those cases. The richness of information that is collected

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Chapter 2 | Psychological Research 45

in clinical or case studies is unmatched by any other single research method. This allows the researcher to
have a very deep understanding of the individuals and the particular phenomenon being studied.

If clinical or case studies provide so much information, why are they not more frequent among
researchers? As it turns out, the major benefit of this particular approach is also a weakness. As mentioned
earlier, this approach is often used when studying individuals who are interesting to researchers because
they have a rare characteristic. Therefore, the individuals who serve as the focus of case studies are not like
most other people. If scientists ultimately want to explain all behavior, focusing attention on such a special
group of people can make it difficult to generalize any observations to the larger population as a whole.
Generalizing refers to the ability to apply the findings of a particular research project to larger segments of
society. Again, case studies provide enormous amounts of information, but since the cases are so specific,
the potential to apply what’s learned to the average person may be very limited.

NATURALISTIC OBSERVATION

If you want to understand how behavior occurs, one of the best ways to gain information is to simply
observe the behavior in its natural context. However, people might change their behavior in unexpected
ways if they know they are being observed. How do researchers obtain accurate information when people
tend to hide their natural behavior? As an example, imagine that your professor asks everyone in your
class to raise their hand if they always wash their hands after using the restroom. Chances are that almost
everyone in the classroom will raise their hand, but do you think hand washing after every trip to the
restroom is really that universal?

This is very similar to the phenomenon mentioned earlier in this chapter: many individuals do not feel
comfortable answering a question honestly. But if we are committed to finding out the facts about hand
washing, we have other options available to us.

Suppose we send a classmate into the restroom to actually watch whether everyone washes their hands
after using the restroom. Will our observer blend into the restroom environment by wearing a white
lab coat, sitting with a clipboard, and staring at the sinks? We want our researcher to be
inconspicuous—perhaps standing at one of the sinks pretending to put in contact lenses while secretly
recording the relevant information. This type of observational study is called naturalistic observation:
observing behavior in its natural setting. To better understand peer exclusion, Suzanne Fanger
collaborated with colleagues at the University of Texas to observe the behavior of preschool children
on a playground. How did the observers remain inconspicuous over the duration of the study? They
equipped a few of the children with wireless microphones (which the children quickly forgot about) and
observed while taking notes from a distance. Also, the children in that particular preschool (a “laboratory
preschool”) were accustomed to having observers on the playground (Fanger, Frankel, & Hazen, 2012).

It is critical that the observer be as unobtrusive and as inconspicuous as possible: when people know they
are being watched, they are less likely to behave naturally. If you have any doubt about this, ask yourself
how your driving behavior might differ in two situations: In the first situation, you are driving down a
deserted highway during the middle of the day; in the second situation, you are being followed by a police
car down the same deserted highway (Figure 2.7).

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Figure 2.7 Seeing a police car behind you would probably affect your driving behavior. (credit: Michael Gil)

It should be pointed out that naturalistic observation is not limited to research involving humans. Indeed,
some of the best-known examples of naturalistic observation involve researchers going into the field to
observe various kinds of animals in their own environments. As with human studies, the researchers
maintain their distance and avoid interfering with the animal subjects so as not to influence their natural
behaviors. Scientists have used this technique to study social hierarchies and interactions among animals
ranging from ground squirrels to gorillas. The information provided by these studies is invaluable in
understanding how those animals organize socially and communicate with one another. The
anthropologist Jane Goodall, for example, spent nearly five decades observing the behavior of
chimpanzees in Africa (Figure 2.8). As an illustration of the types of concerns that a researcher might
encounter in naturalistic observation, some scientists criticized Goodall for giving the chimps names
instead of referring to them by numbers—using names was thought to undermine the emotional
detachment required for the objectivity of the study (McKie, 2010).

Figure 2.8 (a) Jane Goodall made a career of conducting naturalistic observations of (b) chimpanzee behavior.
(credit “Jane Goodall”: modification of work by Erik Hersman; “chimpanzee”: modification of work by “Afrika
Force”/Flickr.com)

The greatest benefit of naturalistic observation is the validity, or accuracy, of information collected
unobtrusively in a natural setting. Having individuals behave as they normally would in a given situation
means that we have a higher degree of ecological validity, or realism, than we might achieve with
other research approaches. Therefore, our ability to generalize the findings of the research to real-world
situations is enhanced. If done correctly, we need not worry about people or animals modifying their
behavior simply because they are being observed. Sometimes, people may assume that reality programs
give us a glimpse into authentic human behavior. However, the principle of inconspicuous observation
is violated as reality stars are followed by camera crews and are interviewed on camera for personal
confessionals. Given that environment, we must doubt how natural and realistic their behaviors are.

The major downside of naturalistic observation is that they are often difficult to set up and control. In
our restroom study, what if you stood in the restroom all day prepared to record people’s hand washing
behavior and no one came in? Or, what if you have been closely observing a troop of gorillas for weeks
only to find that they migrated to a new place while you were sleeping in your tent? The benefit of realistic
data comes at a cost. As a researcher you have no control of when (or if) you have behavior to observe. In

Chapter 2 | Psychological Research 47

addition, this type of observational research often requires significant investments of time, money, and a
good dose of luck.

Sometimes studies involve structured observation. In these cases, people are observed while engaging in
set, specific tasks. An excellent example of structured observation comes from Strange Situation by Mary
Ainsworth (you will read more about this in the chapter on lifespan development). The Strange Situation is
a procedure used to evaluate attachment styles that exist between an infant and caregiver. In this scenario,
caregivers bring their infants into a room filled with toys. The Strange Situation involves a number of
phases, including a stranger coming into the room, the caregiver leaving the room, and the caregiver’s
return to the room. The infant’s behavior is closely monitored at each phase, but it is the behavior of the
infant upon being reunited with the caregiver that is most telling in terms of characterizing the infant’s
attachment style with the caregiver.

Another potential problem in observational research is observer bias. Generally, people who act as
observers are closely involved in the research project and may unconsciously skew their observations to
fit their research goals or expectations. To protect against this type of bias, researchers should have clear
criteria established for the types of behaviors recorded and how those behaviors should be classified. In
addition, researchers often compare observations of the same event by multiple observers, in order to test
inter-rater reliability: a measure of reliability that assesses the consistency of observations by different
observers.

SURVEYS

Often, psychologists develop surveys as a means of gathering data. Surveys are lists of questions to be
answered by research participants, and can be delivered as paper-and-pencil questionnaires, administered
electronically, or conducted verbally (Figure 2.9). Generally, the survey itself can be completed in a short
time, and the ease of administering a survey makes it easy to collect data from a large number of people.

Surveys allow researchers to gather data from larger samples than may be afforded by other research
methods. A sample is a subset of individuals selected from a population, which is the overall group of
individuals that the researchers are interested in. Researchers study the sample and seek to generalize their
findings to the population. Generally, researchers will begin this process by calculating various measures
of central tendency from the data they have collected. These measures provide an overall summary of what
a typical response looks like. There are three measures of central tendency: mode, median, and mean. The
mode is the most frequently occurring response, the median lies at the middle of a given data set, and the
mean is the arithmetic average of all data points. Means tend to be most useful in conducting additional
analyses like those described below; however, means are very sensitive to the effects of outliers, and so
one must be aware of those effects when making assessments of what measures of central tendency tell us
about a data set in question.

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Figure 2.9 Surveys can be administered in a number of ways, including electronically administered research, like
the survey shown here. (credit: Robert Nyman)

There is both strength and weakness of the survey in comparison to case studies. By using surveys, we
can collect information from a larger sample of people. A larger sample is better able to reflect the actual
diversity of the population, thus allowing better generalizability. Therefore, if our sample is sufficiently
large and diverse, we can assume that the data we collect from the survey can be generalized to the larger
population with more certainty than the information collected through a case study. However, given the
greater number of people involved, we are not able to collect the same depth of information on each person
that would be collected in a case study.

Another potential weakness of surveys is something we touched on earlier in this chapter: People don’t
always give accurate responses. They may lie, misremember, or answer questions in a way that they think
makes them look good. For example, people may report drinking less alcohol than is actually the case.

Any number of research questions can be answered through the use of surveys. One real-world example
is the research conducted by Jenkins, Ruppel, Kizer, Yehl, and Griffin (2012) about the backlash against
the US Arab-American community following the terrorist attacks of September 11, 2001. Jenkins and
colleagues wanted to determine to what extent these negative attitudes toward Arab-Americans still
existed nearly a decade after the attacks occurred. In one study, 140 research participants filled out a
survey with 10 questions, including questions asking directly about the participant’s overt prejudicial
attitudes toward people of various ethnicities. The survey also asked indirect questions about how likely
the participant would be to interact with a person of a given ethnicity in a variety of settings (such as,
“How likely do you think it is that you would introduce yourself to a person of Arab-American descent?”).
The results of the research suggested that participants were unwilling to report prejudicial attitudes
toward any ethnic group. However, there were significant differences between their pattern of responses
to questions about social interaction with Arab-Americans compared to other ethnic groups: they indicated
less willingness for social interaction with Arab-Americans compared to the other ethnic groups. This
suggested that the participants harbored subtle forms of prejudice against Arab-Americans, despite their
assertions that this was not the case (Jenkins et al., 2012).

ARCHIVAL RESEARCH

Some researchers gain access to large amounts of data without interacting with a single research
participant. Instead, they use existing records to answer various research questions. This type of research
approach is known as archival research. Archival research relies on looking at past records or data sets to
look for interesting patterns or relationships.

For example, a researcher might access the academic records of all individuals who enrolled in college
within the past ten years and calculate how long it took them to complete their degrees, as well as course
loads, grades, and extracurricular involvement. Archival research could provide important information

Chapter 2 | Psychological Research 49

about who is most likely to complete their education, and it could help identify important risk factors for
struggling students (Figure 2.10).

Figure 2.10 A researcher doing archival research examines records, whether archived as a (a) hardcopy or (b)
electronically. (credit “paper files”: modification of work by “Newtown graffiti”/Flickr; “computer”: modification of work
by INPIVIC Family/Flickr)

In comparing archival research to other research methods, there are several important distinctions. For
one, the researcher employing archival research never directly interacts with research participants.
Therefore, the investment of time and money to collect data is considerably less with archival research.
Additionally, researchers have no control over what information was originally collected. Therefore,
research questions have to be tailored so they can be answered within the structure of the existing data sets.
There is also no guarantee of consistency between the records from one source to another, which might
make comparing and contrasting different data sets problematic.

LONGITUDINAL AND CROSS-SECTIONAL RESEARCH

Sometimes we want to see how people change over time, as in studies of human development and
lifespan. When we test the same group of individuals repeatedly over an extended period of time, we
are conducting longitudinal research. Longitudinal research is a research design in which data-gathering
is administered repeatedly over an extended period of time. For example, we may survey a group of
individuals about their dietary habits at age 20, retest them a decade later at age 30, and then again at age
40.

Another approach is cross-sectional research. In cross-sectional research, a researcher compares multiple
segments of the population at the same time. Using the dietary habits example above, the researcher might
directly compare different groups of people by age. Instead of studying a group of people for 20 years
to see how their dietary habits changed from decade to decade, the researcher would study a group of
20-year-old individuals and compare them to a group of 30-year-old individuals and a group of 40-year-
old individuals. While cross-sectional research requires a shorter-term investment, it is also limited by
differences that exist between the different generations (or cohorts) that have nothing to do with age per
se, but rather reflect the social and cultural experiences of different generations of individuals make them
different from one another.

To illustrate this concept, consider the following survey findings. In recent years there has been significant
growth in the popular support of same-sex marriage. Many studies on this topic break down survey
participants into different age groups. In general, younger people are more supportive of same-sex
marriage than are those who are older (Jones, 2013). Does this mean that as we age we become less open to
the idea of same-sex marriage, or does this mean that older individuals have different perspectives because
of the social climates in which they grew up? Longitudinal research is a powerful approach because the
same individuals are involved in the research project over time, which means that the researchers need to
be less concerned with differences among cohorts affecting the results of their study.

Often longitudinal studies are employed when researching various diseases in an effort to understand

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particular risk factors. Such studies often involve tens of thousands of individuals who are followed
for several decades. Given the enormous number of people involved in these studies, researchers can
feel confident that their findings can be generalized to the larger population. The Cancer Prevention
Study-3 (CPS-3) is one of a series of longitudinal studies sponsored by the American Cancer Society aimed
at determining predictive risk factors associated with cancer. When participants enter the study, they
complete a survey about their lives and family histories, providing information on factors that might cause
or prevent the development of cancer. Then every few years the participants receive additional surveys
to complete. In the end, hundreds of thousands of participants will be tracked over 20 years to determine
which of them develop cancer and which do not.

Clearly, this type of research is important and potentially very informative. For instance, earlier
longitudinal studies sponsored by the American Cancer Society provided some of the first scientific
demonstrations of the now well-established links between increased rates of cancer and smoking
(American Cancer Society, n.d.) (Figure 2.11).

Figure 2.11 Longitudinal research like the CPS-3 help us to better understand how smoking is associated with
cancer and other diseases. (credit: CDC/Debora Cartagena)

As with any research strategy, longitudinal research is not without limitations. For one, these studies
require an incredible time investment by the researcher and research participants. Given that some
longitudinal studies take years, if not decades, to complete, the results will not be known for a considerable
period of time. In addition to the time demands, these studies also require a substantial financial
investment. Many researchers are unable to commit the resources necessary to see a longitudinal project
through to the end.

Research participants must also be willing to continue their participation for an extended period of time,
and this can be problematic. People move, get married and take new names, get ill, and eventually die.
Even without significant life changes, some people may simply choose to discontinue their participation
in the project. As a result, the attrition rates, or reduction in the number of research participants due to
dropouts, in longitudinal studies are quite high and increases over the course of a project. For this reason,
researchers using this approach typically recruit many participants fully expecting that a substantial
number will drop out before the end. As the study progresses, they continually check whether the sample
still represents the larger population, and make adjustments as necessary.

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2.3 Analyzing Findings

Learning Objectives

By the end of this section, you will be able to:
• Explain what a correlation coefficient tells us about the relationship between variables
• Recognize that correlation does not indicate a cause-and-effect relationship between

variables
• Discuss our tendency to look for relationships between variables that do not really exist
• Explain random sampling and assignment of participants into experimental and control

groups
• Discuss how experimenter or participant bias could affect the results of an experiment
• Identify independent and dependent variables

Did you know that as sales in ice cream increase, so does the overall rate of crime? Is it possible that
indulging in your favorite flavor of ice cream could send you on a crime spree? Or, after committing crime
do you think you might decide to treat yourself to a cone? There is no question that a relationship exists
between ice cream and crime (e.g., Harper, 2013), but it would be pretty foolish to decide that one thing
actually caused the other to occur.

It is much more likely that both ice cream sales and crime rates are related to the temperature outside.
When the temperature is warm, there are lots of people out of their houses, interacting with each other,
getting annoyed with one another, and sometimes committing crimes. Also, when it is warm outside, we
are more likely to seek a cool treat like ice cream. How do we determine if there is indeed a relationship
between two things? And when there is a relationship, how can we discern whether it is attributable to
coincidence or causation?

CORRELATIONAL RESEARCH

Correlation means that there is a relationship between two or more variables (such as ice cream
consumption and crime), but this relationship does not necessarily imply cause and effect. When two
variables are correlated, it simply means that as one variable changes, so does the other. We can measure
correlation by calculating a statistic known as a correlation coefficient. A correlation coefficient is a
number from -1 to +1 that indicates the strength and direction of the relationship between variables. The
correlation coefficient is usually represented by the letter r.

The number portion of the correlation coefficient indicates the strength of the relationship. The closer
the number is to 1 (be it negative or positive), the more strongly related the variables are, and the more
predictable changes in one variable will be as the other variable changes. The closer the number is to zero,
the weaker the relationship, and the less predictable the relationships between the variables becomes. For
instance, a correlation coefficient of 0.9 indicates a far stronger relationship than a correlation coefficient of
0.3. If the variables are not related to one another at all, the correlation coefficient is 0. The example above
about ice cream and crime is an example of two variables that we might expect to have no relationship to
each other.

The sign—positive or negative—of the correlation coefficient indicates the direction of the relationship
(Figure 2.12). A positive correlation means that the variables move in the same direction. Put another
way, it means that as one variable increases so does the other, and conversely, when one variable decreases
so does the other. A negative correlation means that the variables move in opposite directions. If two
variables are negatively correlated, a decrease in one variable is associated with an increase in the other
and vice versa.

The example of ice cream and crime rates is a positive correlation because both variables increase when

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temperatures are warmer. Other examples of positive correlations are the relationship between an
individual’s height and weight or the relationship between a person’s age and number of wrinkles. One
might expect a negative correlation to exist between someone’s tiredness during the day and the number
of hours they slept the previous night: the amount of sleep decreases as the feelings of tiredness increase.
In a real-world example of negative correlation, student researchers at the University of Minnesota found
a weak negative correlation (r = -0.29) between the average number of days per week that students got
fewer than 5 hours of sleep and their GPA (Lowry, Dean, & Manders, 2010). Keep in mind that a negative
correlation is not the same as no correlation. For example, we would probably find no correlation between
hours of sleep and shoe size.

As mentioned earlier, correlations have predictive value. Imagine that you are on the admissions
committee of a major university. You are faced with a huge number of applications, but you are able
to accommodate only a small percentage of the applicant pool. How might you decide who should be
admitted? You might try to correlate your current students’ college GPA with their scores on standardized
tests like the SAT or ACT. By observing which correlations were strongest for your current students, you
could use this information to predict relative success of those students who have applied for admission
into the university.

Figure 2.12 Scatterplots are a graphical view of the strength and direction of correlations. The stronger the
correlation, the closer the data points are to a straight line. In these examples, we see that there is (a) a positive
correlation between weight and height, (b) a negative correlation between tiredness and hours of sleep, and (c) no
correlation between shoe size and hours of sleep.

Manipulate this interactive scatterplot (http://openstax.org/l/scatplot) to practice your understanding
of positive and negative correlation.

Correlation Does Not Indicate Causation

Correlational research is useful because it allows us to discover the strength and direction of relationships
that exist between two variables. However, correlation is limited because establishing the existence of a
relationship tells us little about cause and effect. While variables are sometimes correlated because one
does cause the other, it could also be that some other factor, a confounding variable, is actually causing the
systematic movement in our variables of interest. In the ice cream/crime rate example mentioned earlier,
temperature is a confounding variable that could account for the relationship between the two variables.

Even when we cannot point to clear confounding variables, we should not assume that a correlation
between two variables implies that one variable causes changes in another. This can be frustrating when a

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cause-and-effect relationship seems clear and intuitive. Think back to our discussion of the research done
by the American Cancer Society and how their research projects were some of the first demonstrations of
the link between smoking and cancer. It seems reasonable to assume that smoking causes cancer, but if we
were limited to correlational research, we would be overstepping our bounds by making this assumption.

Unfortunately, people mistakenly make claims of causation as a function of correlations all the time. Such
claims are especially common in advertisements and news stories. For example, recent research found
that people who eat cereal on a regular basis achieve healthier weights than those who rarely eat cereal
(Frantzen, Treviño, Echon, Garcia-Dominic, & DiMarco, 2013; Barton et al., 2005). Guess how the cereal
companies report this finding. Does eating cereal really cause an individual to maintain a healthy weight,
or are there other possible explanations, such as, someone at a healthy weight is more likely to regularly
eat a healthy breakfast than someone who is obese or someone who avoids meals in an attempt to diet
(Figure 2.13)? While correlational research is invaluable in identifying relationships among variables, a
major limitation is the inability to establish causality. Psychologists want to make statements about cause
and effect, but the only way to do that is to conduct an experiment to answer a research question. The next
section describes how scientific experiments incorporate methods that eliminate, or control for, alternative
explanations, which allow researchers to explore how changes in one variable cause changes in another
variable.

Figure 2.13 Does eating cereal really cause someone to be a healthy weight? (credit: Tim Skillern)

Illusory Correlations

The temptation to make erroneous cause-and-effect statements based on correlational research is not
the only way we tend to misinterpret data. We also tend to make the mistake of illusory correlations,
especially with unsystematic observations. Illusory correlations, or false correlations, occur when people
believe that relationships exist between two things when no such relationship exists. One well-known
illusory correlation is the supposed effect that the moon’s phases have on human behavior. Many people
passionately assert that human behavior is affected by the phase of the moon, and specifically, that people
act strangely when the moon is full (Figure 2.14).

Figure 2.14 Many people believe that a full moon makes people behave oddly. (credit: Cory Zanker)

There is no denying that the moon exerts a powerful influence on our planet. The ebb and flow of the
ocean’s tides are tightly tied to the gravitational forces of the moon. Many people believe, therefore, that

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it is logical that we are affected by the moon as well. After all, our bodies are largely made up of water.
A meta-analysis of nearly 40 studies consistently demonstrated, however, that the relationship between
the moon and our behavior does not exist (Rotton & Kelly, 1985). While we may pay more attention to
odd behavior during the full phase of the moon, the rates of odd behavior remain constant throughout the
lunar cycle.

Why are we so apt to believe in illusory correlations like this? Often we read or hear about them and
simply accept the information as valid. Or, we have a hunch about how something works and then look
for evidence to support that hunch, ignoring evidence that would tell us our hunch is false; this is known
as confirmation bias. Other times, we find illusory correlations based on the information that comes most
easily to mind, even if that information is severely limited. And while we may feel confident that we can
use these relationships to better understand and predict the world around us, illusory correlations can
have significant drawbacks. For example, research suggests that illusory correlations—in which certain
behaviors are inaccurately attributed to certain groups—are involved in the formation of prejudicial
attitudes that can ultimately lead to discriminatory behavior (Fiedler, 2004).

CAUSALITY: CONDUCTING EXPERIMENTS AND USING THE DATA

As you’ve learned, the only way to establish that there is a cause-and-effect relationship between two
variables is to conduct a scientific experiment. Experiment has a different meaning in the scientific context
than in everyday life. In everyday conversation, we often use it to describe trying something for the first
time, such as experimenting with a new hair style or a new food. However, in the scientific context, an
experiment has precise requirements for design and implementation.

The Experimental Hypothesis

In order to conduct an experiment, a researcher must have a specific hypothesis to be tested. As you’ve
learned, hypotheses can be formulated either through direct observation of the real world or after careful
review of previous research. For example, if you think that the use of technology in the classroom has
negative impacts on learning, then you have basically formulated a hypothesis—namely, that the use of
technology in the classroom should be limited because it decreases learning. How might you have arrived
at this particular hypothesis? You may have noticed that your classmates who take notes on their laptops
perform at lower levels on class exams than those who take notes by hand, or those who receive a lesson
via a computer program versus via an in-person teacher have different levels of performance when tested
(Figure 2.15).

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Figure 2.15 How might the use of technology in the classroom impact learning? (credit: modification of work by
Nikolay Georgiev/Pixabay)

These sorts of personal observations are what often lead us to formulate a specific hypothesis, but
we cannot use limited personal observations and anecdotal evidence to rigorously test our hypothesis.
Instead, to find out if real-world data supports our hypothesis, we have to conduct an experiment.

Designing an Experiment

The most basic experimental design involves two groups: the experimental group and the control group.
The two groups are designed to be the same except for one difference— experimental manipulation. The
experimental group gets the experimental manipulation—that is, the treatment or variable being tested (in
this case, the use of technology)—and the control group does not. Since experimental manipulation is the
only difference between the experimental and control groups, we can be sure that any differences between
the two are due to experimental manipulation rather than chance.

In our example of how the use of technology should be limited in the classroom, we have the experimental
group learn algebra using a computer program and then test their learning. We measure the learning in
our control group after they are taught algebra by a teacher in a traditional classroom. It is important for
the control group to be treated similarly to the experimental group, with the exception that the control
group does not receive the experimental manipulation.

We also need to precisely define, or operationalize, how we measure learning of algebra. An operational
definition is a precise description of our variables, and it is important in allowing others to understand
exactly how and what a researcher measures in a particular experiment. In operationalizing learning, we
might choose to look at performance on a test covering the material on which the individuals were taught
by the teacher or the computer program. We might also ask our participants to summarize the information
that was just presented in some way. Whatever we determine, it is important that we operationalize
learning in such a way that anyone who hears about our study for the first time knows exactly what we
mean by learning. This aids peoples’ ability to interpret our data as well as their capacity to repeat our
experiment should they choose to do so.

Once we have operationalized what is considered use of technology and what is considered learning in
our experiment participants, we need to establish how we will run our experiment. In this case, we might
have participants spend 45 minutes learning algebra (either through a computer program or with an in-
person math teacher) and then give them a test on the material covered during the 45 minutes.

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Ideally, the people who score the tests are unaware of who was assigned to the experimental or control
group, in order to control for experimenter bias. Experimenter bias refers to the possibility that a
researcher’s expectations might skew the results of the study. Remember, conducting an experiment
requires a lot of planning, and the people involved in the research project have a vested interest in
supporting their hypotheses. If the observers knew which child was in which group, it might influence
how they interpret ambiguous responses, such as sloppy handwriting or minor computational mistakes.
By being blind to which child is in which group, we protect against those biases. This situation is a
single-blind study, meaning that one of the groups (participants) are unaware as to which group they
are in (experiment or control group) while the researcher who developed the experiment knows which
participants are in each group.

In a double-blind study, both the researchers and the participants are blind to group assignments. Why
would a researcher want to run a study where no one knows who is in which group? Because by doing
so, we can control for both experimenter and participant expectations. If you are familiar with the phrase
placebo effect, you already have some idea as to why this is an important consideration. The placebo effect
occurs when people’s expectations or beliefs influence or determine their experience in a given situation.
In other words, simply expecting something to happen can actually make it happen.

The placebo effect is commonly described in terms of testing the effectiveness of a new medication.
Imagine that you work in a pharmaceutical company, and you think you have a new drug that is effective
in treating depression. To demonstrate that your medication is effective, you run an experiment with two
groups: The experimental group receives the medication, and the control group does not. But you don’t
want participants to know whether they received the drug or not.

Why is that? Imagine that you are a participant in this study, and you have just taken a pill that you
think will improve your mood. Because you expect the pill to have an effect, you might feel better simply
because you took the pill and not because of any drug actually contained in the pill—this is the placebo
effect.

To make sure that any effects on mood are due to the drug and not due to expectations, the control group
receives a placebo (in this case a sugar pill). Now everyone gets a pill, and once again neither the researcher
nor the experimental participants know who got the drug and who got the sugar pill. Any differences in
mood between the experimental and control groups can now be attributed to the drug itself rather than to
experimenter bias or participant expectations (Figure 2.16).

Figure 2.16 Providing the control group with a placebo treatment protects against bias caused by expectancy.
(credit: Elaine and Arthur Shapiro)

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Independent and Dependent Variables

In a research experiment, we strive to study whether changes in one thing cause changes in another. To
achieve this, we must pay attention to two important variables, or things that can be changed, in any
experimental study: the independent variable and the dependent variable. An independent variable is
manipulated or controlled by the experimenter. In a well-designed experimental study, the independent
variable is the only important difference between the experimental and control groups. In our example of
how technology use in the classroom affects learning, the independent variable is the type of learning by
participants in the study (Figure 2.17). A dependent variable is what the researcher measures to see how
much effect the independent variable had. In our example, the dependent variable is the learning exhibited
by our participants.

Figure 2.17 In an experiment, manipulations of the independent variable are expected to result in changes in the
dependent variable. (credit: “classroom” modification of work by Nikolay Georgiev/Pixabay; credit “note taking”:
modification of work by KF/Wikimedia)

We expect that the dependent variable will change as a function of the independent variable. In other
words, the dependent variable depends on the independent variable. A good way to think about the
relationship between the independent and dependent variables is with this question: What effect does the
independent variable have on the dependent variable? Returning to our example, what is the effect of
being taught a lesson through a computer program versus through an in-person instructor?

Selecting and Assigning Experimental Participants

Now that our study is designed, we need to obtain a sample of individuals to include in our experiment.
Our study involves human participants so we need to determine who to include. Participants are the
subjects of psychological research, and as the name implies, individuals who are involved in psychological
research actively participate in the process. Often, psychological research projects rely on college students
to serve as participants. In fact, the vast majority of research in psychology subfields has historically
involved students as research participants (Sears, 1986; Arnett, 2008). But are college students truly
representative of the general population? College students tend to be younger, more educated, more
liberal, and less diverse than the general population. Although using students as test subjects is an
accepted practice, relying on such a limited pool of research participants can be problematic because it is
difficult to generalize findings to the larger population.

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Our hypothetical experiment involves high school students, and we must first generate a sample of
students. Samples are used because populations are usually too large to reasonably involve every member
in our particular experiment (Figure 2.18). If possible, we should use a random sample (there are other
types of samples, but for the purposes of this chapter, we will focus on random samples). A random
sample is a subset of a larger population in which every member of the population has an equal chance
of being selected. Random samples are preferred because if the sample is large enough we can be
reasonably sure that the participating individuals are representative of the larger population. This means
that the percentages of characteristics in the sample—sex, ethnicity, socioeconomic level, and any other
characteristics that might affect the results—are close to those percentages in the larger population.

In our example, let’s say we decide our population of interest is algebra students. But all algebra students
is a very large population, so we need to be more specific; instead we might say our population of interest
is all algebra students in a particular city. We should include students from various income brackets,
family situations, races, ethnicities, religions, and geographic areas of town. With this more manageable
population, we can work with the local schools in selecting a random sample of around 200 algebra
students who we want to participate in our experiment.

In summary, because we cannot test all of the algebra students in a city, we want to find a group of about
200 that reflects the composition of that city. With a representative group, we can generalize our findings
to the larger population without fear of our sample being biased in some way.

Figure 2.18 Researchers may work with (a) a large population or (b) a sample group that is a subset of the larger
population. (credit “crowd”: modification of work by James Cridland; credit “students”: modification of work by Laurie
Sullivan)

Now that we have a sample, the next step of the experimental process is to split the participants into
experimental and control groups through random assignment. With random assignment, all participants
have an equal chance of being assigned to either group. There is statistical software that will randomly
assign each of the algebra students in the sample to either the experimental or the control group.

Random assignment is critical for sound experimental design. With sufficiently large samples, random
assignment makes it unlikely that there are systematic differences between the groups. So, for instance, it
would be very unlikely that we would get one group composed entirely of males, a given ethnic identity,
or a given religious ideology. This is important because if the groups were systematically different before
the experiment began, we would not know the origin of any differences we find between the groups: Were
the differences preexisting, or were they caused by manipulation of the independent variable? Random
assignment allows us to assume that any differences observed between experimental and control groups
result from the manipulation of the independent variable.

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Use this online random number generator (http://openstax.org/l/rannumbers) to learn more about
random sampling and assignments.

Issues to Consider

While experiments allow scientists to make cause-and-effect claims, they are not without problems. True
experiments require the experimenter to manipulate an independent variable, and that can complicate
many questions that psychologists might want to address. For instance, imagine that you want to know
what effect sex (the independent variable) has on spatial memory (the dependent variable). Although you
can certainly look for differences between males and females on a task that taps into spatial memory, you
cannot directly control a person’s sex. We categorize this type of research approach as quasi-experimental
and recognize that we cannot make cause-and-effect claims in these circumstances.

Experimenters are also limited by ethical constraints. For instance, you would not be able to conduct an
experiment designed to determine if experiencing abuse as a child leads to lower levels of self-esteem
among adults. To conduct such an experiment, you would need to randomly assign some experimental
participants to a group that receives abuse, and that experiment would be unethical.

Interpreting Experimental Findings

Once data is collected from both the experimental and the control groups, a statistical analysis is
conducted to find out if there are meaningful differences between the two groups. A statistical analysis
determines how likely any difference found is due to chance (and thus not meaningful). For example, if
an experiment is done on the effectiveness of a nutritional supplement, and those taking a placebo pill
(and not the supplement) have the same result as those taking the supplement, then the experiment has
shown that the nutritional supplement is not effective. Generally, psychologists consider differences to be
statistically significant if there is less than a five percent chance of observing them if the groups did not
actually differ from one another. Stated another way, psychologists want to limit the chances of making
“false positive” claims to five percent or less.

The greatest strength of experiments is the ability to assert that any significant differences in the findings
are caused by the independent variable. This occurs because random selection, random assignment, and
a design that limits the effects of both experimenter bias and participant expectancy should create groups
that are similar in composition and treatment. Therefore, any difference between the groups is attributable
to the independent variable, and now we can finally make a causal statement. If we find that watching a
violent television program results in more violent behavior than watching a nonviolent program, we can
safely say that watching violent television programs causes an increase in the display of violent behavior.

Reporting Research

When psychologists complete a research project, they generally want to share their findings with other
scientists. The American Psychological Association (APA) publishes a manual detailing how to write
a paper for submission to scientific journals. Unlike an article that might be published in a magazine
like Psychology Today, which targets a general audience with an interest in psychology, scientific journals
generally publish peer-reviewed journal articles aimed at an audience of professionals and scholars who
are actively involved in research themselves.

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The Online Writing Lab (OWL) (http://openstax.org/l/owl) at Purdue University can walk you through
the APA writing guidelines.

A peer-reviewed journal article is read by several other scientists (generally anonymously) with expertise
in the subject matter. These peer reviewers provide feedback—to both the author and the journal
editor—regarding the quality of the draft. Peer reviewers look for a strong rationale for the research being
described, a clear description of how the research was conducted, and evidence that the research was
conducted in an ethical manner. They also look for flaws in the study’s design, methods, and statistical
analyses. They check that the conclusions drawn by the authors seem reasonable given the observations
made during the research. Peer reviewers also comment on how valuable the research is in advancing the
discipline’s knowledge. This helps prevent unnecessary duplication of research findings in the scientific
literature and, to some extent, ensures that each research article provides new information. Ultimately, the
journal editor will compile all of the peer reviewer feedback and determine whether the article will be
published in its current state (a rare occurrence), published with revisions, or not accepted for publication.

Peer review provides some degree of quality control for psychological research. Poorly conceived or
executed studies can be weeded out, and even well-designed research can be improved by the revisions
suggested. Peer review also ensures that the research is described clearly enough to allow other scientists
to replicate it, meaning they can repeat the experiment using different samples to determine reliability.
Sometimes replications involve additional measures that expand on the original finding. In any case,
each replication serves to provide more evidence to support the original research findings. Successful
replications of published research make scientists more apt to adopt those findings, while repeated failures
tend to cast doubt on the legitimacy of the original article and lead scientists to look elsewhere. For
example, it would be a major advancement in the medical field if a published study indicated that taking
a new drug helped individuals achieve a healthy weight without changing their diet. But if other scientists
could not replicate the results, the original study’s claims would be questioned.

In recent years, there has been increasing concern about a “replication crisis” that has affected a number of
scientific fields, including psychology. Some of the most well-known studies and scientists have produced
research that has failed to be replicated by others (as discussed in Shrout & Rodgers, 2018). In fact, even a
famous Nobel Prize-winning scientist has recently retracted a published paper because she had difficulty
replicating her results (Nobel Prize-winning scientist Frances Arnold retracts paper, 2020 January 3). These
kinds of outcomes have prompted some scientists to begin to work together and more openly, and some
would argue that the current “crisis” is actually improving the ways in which science is conducted and in
how its results are shared with others (Aschwanden, 2018).

The Vaccine-Autism Myth and Retraction of Published Studies

Some scientists have claimed that routine childhood vaccines cause some children to develop autism, and,
in fact, several peer-reviewed publications published research making these claims. Since the initial reports,
large-scale epidemiological research has suggested that vaccinations are not responsible for causing autism
and that it is much safer to have your child vaccinated than not. Furthermore, several of the original studies
making this claim have since been retracted.

A published piece of work can be rescinded when data is called into question because of falsification,

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fabrication, or serious research design problems. Once rescinded, the scientific community is informed that
there are serious problems with the original publication. Retractions can be initiated by the researcher who
led the study, by research collaborators, by the institution that employed the researcher, or by the editorial
board of the journal in which the article was originally published. In the vaccine-autism case, the retraction
was made because of a significant conflict of interest in which the leading researcher had a financial interest
in establishing a link between childhood vaccines and autism (Offit, 2008). Unfortunately, the initial studies
received so much media attention that many parents around the world became hesitant to have their children
vaccinated (Figure 2.19). Continued reliance on such debunked studies has significant consequences. For
instance, between January and October of 2019, there were 22 measles outbreaks across the United States
and more than a thousand cases of individuals contracting measles (Patel et al., 2019). This is likely due to
the anti-vaccination movements that have risen from the debunked research. For more information about how
the vaccine/autism story unfolded, as well as the repercussions of this story, take a look at Paul Offit’s book,
Autism’s False Prophets: Bad Science, Risky Medicine, and the Search for a Cure.

Figure 2.19 Some people still think vaccinations cause autism. (credit: modification of work by UNICEF
Sverige)

RELIABILITY AND VALIDITY

Reliability and validity are two important considerations that must be made with any type of data
collection. Reliability refers to the ability to consistently produce a given result. In the context of
psychological research, this would mean that any instruments or tools used to collect data do so in
consistent, reproducible ways. There are a number of different types of reliability. Some of these include
inter-rater reliability (the degree to which two or more different observers agree on what has been
observed), internal consistency (the degree to which different items on a survey that measure the same
thing correlate with one another), and test-retest reliability (the degree to which the outcomes of a
particular measure remain consistent over multiple administrations).

Unfortunately, being consistent in measurement does not necessarily mean that you have measured
something correctly. To illustrate this concept, consider a kitchen scale that would be used to measure the
weight of cereal that you eat in the morning. If the scale is not properly calibrated, it may consistently
under- or overestimate the amount of cereal that’s being measured. While the scale is highly reliable in

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producing consistent results (e.g., the same amount of cereal poured onto the scale produces the same
reading each time), those results are incorrect. This is where validity comes into play. Validity refers to
the extent to which a given instrument or tool accurately measures what it’s supposed to measure, and
once again, there are a number of ways in which validity can be expressed. Ecological validity (the degree
to which research results generalize to real-world applications), construct validity (the degree to which a
given variable actually captures or measures what it is intended to measure), and face validity (the degree
to which a given variable seems valid on the surface) are just a few types that researchers consider. While
any valid measure is by necessity reliable, the reverse is not necessarily true. Researchers strive to use
instruments that are both highly reliable and valid.

How Valid Are the SAT and ACT?

Standardized tests like the SAT and ACT are supposed to measure an individual’s aptitude for a college
education, but how reliable and valid are such tests? Research conducted by the College Board suggests that
scores on the SAT have high predictive validity for first-year college students’ GPA (Kobrin, Patterson, Shaw,
Mattern, & Barbuti, 2008). In this context, predictive validity refers to the test’s ability to effectively predict
the GPA of college freshmen. Given that many institutions of higher education require the SAT or ACT for
admission, this high degree of predictive validity might be comforting.

However, the emphasis placed on SAT or ACT scores in college admissions has generated some controversy
on a number of fronts. For one, some researchers assert that these tests are biased and place minority
students at a disadvantage and unfairly reduces the likelihood of being admitted into a college (Santelices &
Wilson, 2010). Additionally, some research has suggested that the predictive validity of these tests is grossly
exaggerated in how well they are able to predict the GPA of first-year college students. In fact, it has been
suggested that the SAT’s predictive validity may be overestimated by as much as 150% (Rothstein, 2004).
Many institutions of higher education are beginning to consider de-emphasizing the significance of SAT scores
in making admission decisions (Rimer, 2008).

Recent examples of high profile cheating scandals both domestically and abroad have only increased the
scrutiny being placed on these types of tests, and as of March 2019, more than 1000 institutions of higher
education have either relaxed or eliminated the requirements for SAT or ACT testing for admissions (Strauss,
2019, March 19).

2.4 Ethics

Learning Objectives

By the end of this section, you will be able to:
• Discuss how research involving human subjects is regulated
• Summarize the processes of informed consent and debriefing
• Explain how research involving animal subjects is regulated

Today, scientists agree that good research is ethical in nature and is guided by a basic respect for human
dignity and safety. However, as you will read in the feature box, this has not always been the case. Modern
researchers must demonstrate that the research they perform is ethically sound. This section presents how
ethical considerations affect the design and implementation of research conducted today.

RESEARCH INVOLVING HUMAN PARTICIPANTS

Any experiment involving the participation of human subjects is governed by extensive, strict guidelines

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designed to ensure that the experiment does not result in harm. Any research institution that receives
federal support for research involving human participants must have access to an institutional review
board (IRB). The IRB is a committee of individuals often made up of members of the institution’s
administration, scientists, and community members (Figure 2.20). The purpose of the IRB is to review
proposals for research that involves human participants. The IRB reviews these proposals with the
principles mentioned above in mind, and generally, approval from the IRB is required in order for the
experiment to proceed.

Figure 2.20 An institution’s IRB meets regularly to review experimental proposals that involve human participants.
(credit: International Hydropower Association/Flickr)

An institution’s IRB requires several components in any experiment it approves. For one, each participant
must sign an informed consent form before they can participate in the experiment. An informed consent
form provides a written description of what participants can expect during the experiment, including
potential risks and implications of the research. It also lets participants know that their involvement is
completely voluntary and can be discontinued without penalty at any time. Furthermore, the informed
consent guarantees that any data collected in the experiment will remain completely confidential. In cases
where research participants are under the age of 18, the parents or legal guardians are required to sign the
informed consent form.

View this example of a consent form (http://openstax.org/l/consentform) to learn more.

While the informed consent form should be as honest as possible in describing exactly what participants
will be doing, sometimes deception is necessary to prevent participants’ knowledge of the exact research
question from affecting the results of the study. Deception involves purposely misleading experiment
participants in order to maintain the integrity of the experiment, but not to the point where the deception
could be considered harmful. For example, if we are interested in how our opinion of someone is affected
by their attire, we might use deception in describing the experiment to prevent that knowledge from
affecting participants’ responses. In cases where deception is involved, participants must receive a full
debriefing upon conclusion of the study—complete, honest information about the purpose of the
experiment, how the data collected will be used, the reasons why deception was necessary, and
information about how to obtain additional information about the study.

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Ethics and the Tuskegee Syphilis Study

Unfortunately, the ethical guidelines that exist for research today were not always applied in the past. In 1932,
poor, rural, black, male sharecroppers from Tuskegee, Alabama, were recruited to participate in an experiment
conducted by the U.S. Public Health Service, with the aim of studying syphilis in black men (Figure 2.21). In
exchange for free medical care, meals, and burial insurance, 600 men agreed to participate in the study. A little
more than half of the men tested positive for syphilis, and they served as the experimental group (given that
the researchers could not randomly assign participants to groups, this represents a quasi-experiment). The
remaining syphilis-free individuals served as the control group. However, those individuals that tested positive
for syphilis were never informed that they had the disease.

While there was no treatment for syphilis when the study began, by 1947 penicillin was recognized as an
effective treatment for the disease. Despite this, no penicillin was administered to the participants in this
study, and the participants were not allowed to seek treatment at any other facilities if they continued in the
study. Over the course of 40 years, many of the participants unknowingly spread syphilis to their wives (and
subsequently their children born from their wives) and eventually died because they never received treatment
for the disease. This study was discontinued in 1972 when the experiment was discovered by the national
press (Tuskegee University, n.d.). The resulting outrage over the experiment led directly to the National
Research Act of 1974 and the strict ethical guidelines for research on humans described in this chapter. Why
is this study unethical? How were the men who participated and their families harmed as a function of this
research?

Figure 2.21 A participant in the Tuskegee Syphilis Study receives an injection.

Visit this website about the Tuskegee Syphilis Study (http://openstax.org/l/tuskegee) to learn more.

RESEARCH INVOLVING ANIMAL SUBJECTS

Many psychologists conduct research involving animal subjects. Often, these researchers use rodents
(Figure 2.22) or birds as the subjects of their experiments—the APA estimates that 90% of all animal
research in psychology uses these species (American Psychological Association, n.d.). Because many basic
processes in animals are sufficiently similar to those in humans, these animals are acceptable substitutes

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for research that would be considered unethical in human participants.

Figure 2.22 Rats, like the one shown here, often serve as the subjects of animal research.

This does not mean that animal researchers are immune to ethical concerns. Indeed, the humane and
ethical treatment of animal research subjects is a critical aspect of this type of research. Researchers must
design their experiments to minimize any pain or distress experienced by animals serving as research
subjects.

Whereas IRBs review research proposals that involve human participants, animal experimental proposals
are reviewed by an Institutional Animal Care and Use Committee (IACUC). An IACUC consists of
institutional administrators, scientists, veterinarians, and community members. This committee is charged
with ensuring that all experimental proposals require the humane treatment of animal research subjects. It
also conducts semi-annual inspections of all animal facilities to ensure that the research protocols are being
followed. No animal research project can proceed without the committee’s approval.

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archival research

attrition

cause-and-effect relationship

clinical or case study

confirmation bias

confounding variable

control group

correlation

correlation coefficient

cross-sectional research

debriefing

deception

deductive reasoning

dependent variable

double-blind study

empirical

experimental group

experimenter bias

fact

falsifiable

Key Terms

method of research using past records or data sets to answer various research
questions, or to search for interesting patterns or relationships

reduction in number of research participants as some drop out of the study over time

changes in one variable cause the changes in the other variable; can be
determined only through an experimental research design

observational research study focusing on one or a few people

tendency to ignore evidence that disproves ideas or beliefs

unanticipated outside factor that affects both variables of interest, often giving the
false impression that changes in one variable causes changes in the other variable, when, in actuality, the
outside factor causes changes in both variables

serves as a basis for comparison and controls for chance factors that might influence the
results of the study—by holding such factors constant across groups so that the experimental
manipulation is the only difference between groups

relationship between two or more variables; when two variables are correlated, one variable
changes as the other does

number from -1 to +1, indicating the strength and direction of the relationship
between variables, and usually represented by r

compares multiple segments of a population at a single time

when an experiment involved deception, participants are told complete and truthful
information about the experiment at its conclusion

purposely misleading experiment participants in order to maintain the integrity of the
experiment

results are predicted based on a general premise

variable that the researcher measures to see how much effect the independent
variable had

experiment in which both the researchers and the participants are blind to group
assignments

grounded in objective, tangible evidence that can be observed time and time again, regardless
of who is observing

group designed to answer the research question; experimental manipulation is the
only difference between the experimental and control groups, so any differences between the two are due
to experimental manipulation rather than chance

researcher expectations skew the results of the study

objective and verifiable observation, established using evidence collected through empirical research

able to be disproven by experimental results

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generalize

hypothesis

illusory correlation

independent variable

inductive reasoning

informed consent

Institutional Animal Care and Use Committee (IACUC)

Institutional Review Board (IRB)

inter-rater reliability

longitudinal research

naturalistic observation

negative correlation

observer bias

operational definition

opinion

participants

peer-reviewed journal article

placebo effect

population

positive correlation

random assignment

inferring that the results for a sample apply to the larger population

(plural: hypotheses) tentative and testable statement about the relationship between two or
more variables

seeing relationships between two things when in reality no such relationship exists

variable that is influenced or controlled by the experimenter; in a sound
experimental study, the independent variable is the only important difference between the experimental
and control group

conclusions are drawn from observations

process of informing a research participant about what to expect during an
experiment, any risks involved, and the implications of the research, and then obtaining the person’s
consent to participate

committee of administrators, scientists,
veterinarians, and community members that reviews proposals for research involving non-human
animals

committee of administrators, scientists, and community members that
reviews proposals for research involving human participants

measure of agreement among observers on how they record and classify a
particular event

studies in which the same group of individuals is surveyed or measured
repeatedly over an extended period of time

observation of behavior in its natural setting

two variables change in different directions, with one becoming larger as the other
becomes smaller; a negative correlation is not the same thing as no correlation

when observations may be skewed to align with observer expectations

description of what actions and operations will be used to measure the dependent
variables and manipulate the independent variables

personal judgments, conclusions, or attitudes that may or may not be accurate

subjects of psychological research

article read by several other scientists (usually anonymously) with
expertise in the subject matter, who provide feedback regarding the quality of the manuscript before it is
accepted for publication

people’s expectations or beliefs influencing or determining their experience in a given
situation

overall group of individuals that the researchers are interested in

two variables change in the same direction, both becoming either larger or smaller

method of experimental group assignment in which all participants have an equal
chance of being assigned to either group

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random sample

reliability

replicate

sample

single-blind study

statistical analysis

survey

theory

validity

subset of a larger population in which every member of the population has an equal
chance of being selected

consistency and reproducibility of a given result

repeating an experiment using different samples to determine the research’s reliability

subset of individuals selected from the larger population

experiment in which the researcher knows which participants are in the experimental
group and which are in the control group

determines how likely any difference between experimental groups is due to chance

list of questions to be answered by research participants—given as paper-and-pencil
questionnaires, administered electronically, or conducted verbally—allowing researchers to collect data
from a large number of people

well-developed set of ideas that propose an explanation for observed phenomena

accuracy of a given result in measuring what it is designed to measure

Summary

2.1 Why Is Research Important?
Scientists are engaged in explaining and understanding how the world around them works, and they are
able to do so by coming up with theories that generate hypotheses that are testable and falsifiable. Theories
that stand up to their tests are retained and refined, while those that do not are discarded or modified.
In this way, research enables scientists to separate fact from simple opinion. Having good information
generated from research aids in making wise decisions both in public policy and in our personal lives.

2.2 Approaches to Research
The clinical or case study involves studying just a few individuals for an extended period of time. While
this approach provides an incredible depth of information, the ability to generalize these observations to
the larger population is problematic. Naturalistic observation involves observing behavior in a natural
setting and allows for the collection of valid, true-to-life information from realistic situations. However,
naturalistic observation does not allow for much control and often requires quite a bit of time and money
to perform. Researchers strive to ensure that their tools for collecting data are both reliable (consistent and
replicable) and valid (accurate).

Surveys can be administered in a number of ways and make it possible to collect large amounts of data
quickly. However, the depth of information that can be collected through surveys is somewhat limited
compared to a clinical or case study.

Archival research involves studying existing data sets to answer research questions.

Longitudinal research has been incredibly helpful to researchers who need to collect data on how people
change over time. Cross-sectional research compares multiple segments of a population at a single time.

2.3 Analyzing Findings
A correlation is described with a correlation coefficient, r, which ranges from -1 to 1. The correlation
coefficient tells us about the nature (positive or negative) and the strength of the relationship between
two or more variables. Correlations do not tell us anything about causation—regardless of how strong
the relationship is between variables. In fact, the only way to demonstrate causation is by conducting an
experiment. People often make the mistake of claiming that correlations exist when they really do not.

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Researchers can test cause-and-effect hypotheses by conducting experiments. Ideally, experimental
participants are randomly selected from the population of interest. Then, the participants are randomly
assigned to their respective groups. Sometimes, the researcher and the participants are blind to group
membership to prevent their expectations from influencing the results.

In ideal experimental design, the only difference between the experimental and control groups is whether
participants are exposed to the experimental manipulation. Each group goes through all phases of the
experiment, but each group will experience a different level of the independent variable: the experimental
group is exposed to the experimental manipulation, and the control group is not exposed to the
experimental manipulation. The researcher then measures the changes that are produced in the dependent
variable in each group. Once data is collected from both groups, it is analyzed statistically to determine if
there are meaningful differences between the groups.

Psychologists report their research findings in peer-reviewed journal articles. Research published in this
format is checked by several other psychologists who serve as a filter separating ideas that are supported
by evidence from ideas that are not. Replication has an important role in ensuring the legitimacy of
published research. In the long run, only those findings that are capable of being replicated consistently
will achieve consensus in the scientific community.

2.4 Ethics
Ethics in research is an evolving field, and some practices that were accepted or tolerated in the past
would be considered unethical today. Researchers are expected to adhere to basic ethical guidelines when
conducting experiments that involve human participants. Any experiment involving human participants
must be approved by an IRB. Participation in experiments is voluntary and requires informed consent of
the participants. If any deception is involved in the experiment, each participant must be fully debriefed
upon the conclusion of the study.

Animal research is also held to a high ethical standard. Researchers who use animals as experimental
subjects must design their projects so that pain and distress are minimized. Animal research requires the
approval of an IACUC, and all animal facilities are subject to regular inspections to ensure that animals are
being treated humanely.

Review Questions

1. Scientific hypotheses are ________ and
falsifiable.

a. observable
b. original
c. provable
d. testable

2. ________ are defined as observable realities.
a. behaviors
b. facts
c. opinions
d. theories

3. Scientific knowledge is ________.
a. intuitive
b. empirical
c. permanent
d. subjective

4. A major criticism of Freud’s early theories
involves the fact that his theories ________.

a. were too limited in scope
b. were too outrageous
c. were too broad
d. were not testable

5. Sigmund Freud developed his theory of
human personality by conducting in-depth
interviews over an extended period of time with a
few clients. This type of research approach is
known as a(n): ________.

a. archival research
b. case study
c. naturalistic observation
d. survey

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6. ________ involves observing behavior in
individuals in their natural environments.

a. archival research
b. case study
c. naturalistic observation
d. survey

7. The major limitation of case studies is
________.

a. the superficial nature of the information
collected in this approach

b. the lack of control that the researcher has in
this approach

c. the inability to generalize the findings from
this approach to the larger population

d. the absence of inter-rater reliability

8. The benefit of naturalistic observation studies
is ________.

a. the honesty of the data that is collected in a
realistic setting

b. how quick and easy these studies are to
perform

c. the researcher’s capacity to make sure that
data is collected as efficiently as possible

d. the ability to determine cause and effect in
this particular approach

9. Using existing records to try to answer a
research question is known as ________.

a. naturalistic observation
b. survey research
c. longitudinal research
d. archival research

10. ________ involves following a group of
research participants for an extended period of
time.

a. archival research
b. longitudinal research
c. naturalistic observation
d. cross-sectional research

11. A(n) ________ is a list of questions developed
by a researcher that can be administered in paper
form.

a. archive
b. case Study
c. naturalistic observation
d. survey

12. Longitudinal research is complicated by high
rates of ________.

a. deception
b. observation
c. attrition
d. generalization

13. Height and weight are positively correlated.
This means that:

a. There is no relationship between height and
weight.

b. Usually, the taller someone is, the thinner
they are.

c. Usually, the shorter someone is, the heavier
they are.

d. As height increases, typically weight
increases.

14. Which of the following correlation coefficients
indicates the strongest relationship between two
variables?

a. –.90
b. –.50
c. +.80
d. +.25

15. Which statement best illustrates a negative
correlation between the number of hours spent
watching TV the week before an exam and the
grade on that exam?

a. Watching too much television leads to poor
exam performance.

b. Smart students watch less television.
c. Viewing television interferes with a

student’s ability to prepare for the
upcoming exam.

d. Students who watch more television
perform more poorly on their exams.

16. The correlation coefficient indicates the
weakest relationship when ________.

a. it is closest to 0
b. it is closest to -1
c. it is positive
d. it is negative

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17. ________ means that everyone in the
population has the same likelihood of being asked
to participate in the study.

a. operationalizing
b. placebo effect
c. random assignment
d. random sampling

18. The ________ is controlled by the
experimenter, while the ________ represents the
information collected and statistically analyzed by
the experimenter.

a. dependent variable; independent variable
b. independent variable; dependent variable
c. placebo effect; experimenter bias
d. experiment bias; placebo effect

19. Researchers must ________ important
concepts in their studies so others would have a
clear understanding of exactly how those concepts
were defined.

a. randomly assign
b. randomly select
c. operationalize
d. generalize

20. Sometimes, researchers will administer a(n)
________ to participants in the control group to
control for the effects that participant expectation
might have on the experiment.

a. dependent variable
b. independent variable
c. statistical analysis
d. placebo

21. ________ is to animal research as ________ is
to human research.

a. informed consent; deception
b. IACUC; IRB
c. IRB; IACUC
d. deception; debriefing

22. Researchers might use ________ when
providing participants with the full details of the
experiment could skew their responses.

a. informed consent
b. deception
c. ethics
d. debriefing

23. A person’s participation in a research project
must be ________.

a. random
b. rewarded
c. voluntary
d. public

24. Before participating in an experiment,
individuals should read and sign the ________
form.

a. informed consent
b. debriefing
c. IRB
d. ethics

Critical Thinking Questions

25. In this section, the D.A.R.E. program was described as an incredibly popular program in schools
across the United States despite the fact that research consistently suggests that this program is largely
ineffective. How might one explain this discrepancy?

26. The scientific method is often described as self-correcting and cyclical. Briefly describe your
understanding of the scientific method with regard to these concepts.

27. In this section, conjoined twins, Krista and Tatiana, were described as being potential participants in a
case study. In what other circumstances would you think that this particular research approach would be
especially helpful and why?

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28. Presumably, reality television programs aim to provide a realistic portrayal of the behavior displayed
by the characters featured in such programs. This section pointed out why this is not really the case. What
changes could be made in the way that these programs are produced that would result in more honest
portrayals of realistic behavior?

29. Which of the research methods discussed in this section would be best suited to research the
effectiveness of the D.A.R.E. program in preventing the use of alcohol and other drugs? Why?

30. Aside from biomedical research, what other areas of research could greatly benefit by both
longitudinal and archival research?

31. Earlier in this section, we read about research suggesting that there is a correlation between eating
cereal and weight. Cereal companies that present this information in their advertisements could lead
someone to believe that eating more cereal causes healthy weight. Why would they make such a claim and
what arguments could you make to counter this cause-and-effect claim?

32. Recently a study was published in the journal, Nutrition and Cancer, which established a negative
correlation between coffee consumption and breast cancer. Specifically, it was found that women
consuming more than 5 cups of coffee a day were less likely to develop breast cancer than women who
never consumed coffee (Lowcock, Cotterchio, Anderson, Boucher, & El-Sohemy, 2013). Imagine you see
a newspaper story about this research that says, “Coffee Protects Against Cancer.” Why is this headline
misleading and why would a more accurate headline draw less interest?

33. Sometimes, true random sampling can be very difficult to obtain. Many researchers make use of
convenience samples as an alternative. For example, one popular convenience sample would involve
students enrolled in Introduction to Psychology courses. What are the implications of using this sampling
technique?

34. Peer review is an important part of publishing research findings in many scientific disciplines. This
process is normally conducted anonymously; in other words, the author of the article being reviewed does
not know who is reviewing the article, and the reviewers are unaware of the author’s identity. Why would
this be an important part of this process?

35. Some argue that animal research is inherently flawed in terms of being ethical because unlike human
participants, animals do not consent to be involved in research. Do you agree with this perspective? Given
that animals do not consent to be involved in research projects, what sorts of extra precautions should be
taken to ensure that they receive the most humane treatment possible?

36. At the end of the last section, you were asked to design a basic experiment to answer some question
of interest. What ethical considerations should be made with the study you proposed to ensure that your
experiment would conform to the scientific community’s expectations of ethical research?

Personal Application Questions

37. Healthcare professionals cite an enormous number of health problems related to obesity, and many
people have an understandable desire to attain a healthy weight. There are many diet programs, services,
and products on the market to aid those who wish to lose weight. If a close friend was considering
purchasing or participating in one of these products, programs, or services, how would you make sure
your friend was fully aware of the potential consequences of this decision? What sort of information would
you want to review before making such an investment or lifestyle change yourself?

Chapter 2 | Psychological Research 73

38. A friend of yours is working part-time in a local pet store. Your friend has become increasingly
interested in how dogs normally communicate and interact with each other, and is thinking of visiting a
local veterinary clinic to see how dogs interact in the waiting room. After reading this section, do you think
this is the best way to better understand such interactions? Do you have any suggestions that might result
in more valid data?

39. As a college student, you are no doubt concerned about the grades that you earn while completing
your coursework. If you wanted to know how overall GPA is related to success in life after college, how
would you choose to approach this question and what kind of resources would you need to conduct this
research?

40. We all have a tendency to make illusory correlations from time to time. Try to think of an illusory
correlation that is held by you, a family member, or a close friend. How do you think this illusory
correlation came about and what can be done in the future to combat them?

41. Are there any questions about human or animal behavior that you would really like to answer?
Generate a hypothesis and briefly describe how you would conduct an experiment to answer your
question.

42. Take a few minutes to think about all of the advancements that our society has achieved as a function
of research involving animal subjects. How have you, a friend, or a family member benefited directly from
this kind of research?

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Chapter 3

Biopsychology

Figure 3.1 Different brain imaging techniques provide scientists with insight into different aspects of how the human
brain functions. Left to right, PET scan (positron emission tomography), CT scan (computerized tomography), and
fMRI (functional magnetic resonance imaging) are three types of scans. (credit “left”: modification of work by Health
and Human Services Department, National Institutes of Health; credit “center”: modification of work by
“Aceofhearts1968″/Wikimedia Commons; credit “right”: modification of work by Kim J, Matthews NL, Park S.)

Chapter Outline

3.1 Human Genetics

3.2 Cells of the Nervous System

3.3 Parts of the Nervous System

3.4 The Brain and Spinal Cord

3.5 The Endocrine System

Introduction

Have you ever taken a device apart to find out how it works? Many of us have done so, whether to attempt
a repair or simply to satisfy our curiosity. A device’s internal workings are often distinct from its user
interface on the outside. For example, we don’t think about microchips and circuits when we turn up
the volume on a mobile phone; instead, we think about getting the volume just right. Similarly, the inner
workings of the human body are often distinct from the external expression of those workings. It is the
job of psychologists to find the connection between these—for example, to figure out how the firings of
millions of neurons become a thought.

This chapter strives to explain the biological mechanisms that underlie behavior. These physiological and
anatomical foundations are the basis for many areas of psychology. In this chapter, you will learn how
genetics influence both physiological and psychological traits. You will become familiar with the structure
and function of the nervous system. And, finally, you will learn how the nervous system interacts with the
endocrine system.

Chapter 3 | Biopsychology 75

3.1 Human Genetics

Learning Objectives

By the end of this section, you will be able to:
• Explain the basic principles of the theory of evolution by natural selection
• Describe the differences between genotype and phenotype
• Discuss how gene-environment interactions are critical for expression of physical and

psychological characteristics

Psychological researchers study genetics in order to better understand the biological factors that contribute
to certain behaviors. While all humans share certain biological mechanisms, we are each unique. And
while our bodies have many of the same parts—brains and hormones and cells with genetic codes—these
are expressed in a wide variety of behaviors, thoughts, and reactions.

Why do two people infected by the same disease have different outcomes: one surviving and one
succumbing to the ailment? How are genetic diseases passed through family lines? Are there genetic
components to psychological disorders, such as depression or schizophrenia? To what extent might there
be a psychological basis to health conditions such as childhood obesity?

To explore these questions, let’s start by focusing on a specific genetic disorder, sickle cell anemia, and
how it might manifest in two affected sisters. Sickle-cell anemia is a genetic condition in which red blood
cells, which are normally round, take on a crescent-like shape (Figure 3.2). The changed shape of these
cells affects how they function: sickle-shaped cells can clog blood vessels and block blood flow, leading to
high fever, severe pain, swelling, and tissue damage.

Figure 3.2 Normal blood cells travel freely through the blood vessels, while sickle-shaped cells form blockages
preventing blood flow.

Many people with sickle-cell anemia—and the particular genetic mutation that causes it—die at an early
age. While the notion of “survival of the fittest” may suggest that people suffering from this disorder have
a low survival rate and therefore the disorder will become less common, this is not the case. Despite the
negative evolutionary effects associated with this genetic mutation, the sickle-cell gene remains relatively
common among people of African descent. Why is this? The explanation is illustrated with the following
scenario.

Imagine two young women—Luwi and Sena—sisters in rural Zambia, Africa. Luwi carries the gene for
sickle-cell anemia; Sena does not carry the gene. Sickle-cell carriers have one copy of the sickle-cell gene but
do not have full-blown sickle-cell anemia. They experience symptoms only if they are severely dehydrated
or are deprived of oxygen (as in mountain climbing). Carriers are thought to be immune from malaria
(an often deadly disease that is widespread in tropical climates) because changes in their blood chemistry

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and immune functioning prevent the malaria parasite from having its effects (Gong, Parikh, Rosenthal, &
Greenhouse, 2013). However, full-blown sickle-cell anemia, with two copies of the sickle-cell gene, does
not provide immunity to malaria.

While walking home from school, both sisters are bitten by mosquitos carrying the malaria parasite. Luwi
is protected against malaria because she carries the sickle-cell mutation. Sena, on the other hand, develops
malaria and dies just two weeks later. Luwi survives and eventually has children, to whom she may pass
on the sickle-cell mutation.

Visit this website about how a mutation in DNA leads to sickle cell anemia (http://openstax.org/l/
sickle1) to learn more.

Malaria is rare in the United States, so the sickle-cell gene benefits nobody: the gene manifests primarily
in minor health problems for carriers with one copy, or a severe full-blown disease with no health benefits
for carriers with two copies. However, the situation is quite different in other parts of the world. In parts of
Africa where malaria is prevalent, having the sickle-cell mutation does provide health benefits for carriers
(protection from malaria).

The story of malaria fits with Charles Darwin’s theory of evolution by natural selection (Figure 3.3). In
simple terms, the theory states that organisms that are better suited for their environment will survive and
reproduce, while those that are poorly suited for their environment will die off. In our example, we can see
that, as a carrier, Luwi’s mutation is highly adaptive in her African homeland; however, if she resided in
the United States (where malaria is rare), her mutation could prove costly—with a high probability of the
disease in her descendants and minor health problems of her own.

Figure 3.3 (a) In 1859, Charles Darwin proposed his theory of evolution by natural selection in his book, On the
Origin of Species. (b) The book contains just one illustration: this diagram that shows how species evolve over time
through natural selection.

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Two Perspectives on Genetics and Behavior

It’s easy to get confused about two fields that study the interaction of genes and the environment, such as the
fields of evolutionary psychology and behavioral genetics. How can we tell them apart?

In both fields, it is understood that genes not only code for particular traits, but also contribute to certain
patterns of cognition and behavior. Evolutionary psychology focuses on how universal patterns of behavior
and cognitive processes have evolved over time. Therefore, variations in cognition and behavior would make
individuals more or less successful in reproducing and passing those genes on to their offspring. Evolutionary
psychologists study a variety of psychological phenomena that may have evolved as adaptations, including
fear response, food preferences, mate selection, and cooperative behaviors (Confer et al., 2010).

Whereas evolutionary psychologists focus on universal patterns that evolved over millions of years, behavioral
geneticists study how individual differences arise, in the present, through the interaction of genes and the
environment. When studying human behavior, behavioral geneticists often employ twin and adoption studies
to research questions of interest. Twin studies compare the likelihood that a given behavioral trait is shared
among identical and fraternal twins; adoption studies compare those rates among biologically related relatives
and adopted relatives. Both approaches provide some insight into the relative importance of genes and
environment for the expression of a given trait.

Watch this interview with renowned evolutionary psychologist David Buss (http://openstax.org/l/
buss) to learn more about how a psychologist approaches evolution and how this approach fits within the
social sciences.

GENETIC VARIATION

Genetic variation, the genetic difference between individuals, is what contributes to a species’ adaptation
to its environment. In humans, genetic variation begins with an egg, about 100 million sperm, and
fertilization. Fertile women ovulate roughly once per month, releasing an egg from follicles in the ovary.
During the egg’s journey from the ovary through the fallopian tubes, to the uterus, a sperm may fertilize
the egg.

The egg and the sperm each contain 23 chromosomes. Chromosomes are long strings of genetic material
known as deoxyribonucleic acid (DNA). DNA is a helix-shaped molecule made up of nucleotide base
pairs. In each chromosome, sequences of DNA make up genes that control or partially control a number
of visible characteristics, known as traits, such as eye color, hair color, and so on. A single gene may have
multiple possible variations, or alleles. An allele is a specific version of a gene. So, a given gene may code
for the trait of hair color, and the different alleles of that gene affect which hair color an individual has.

When a sperm and egg fuse, their 23 chromosomes combine to create a zygote with 46 chromosomes
(23 pairs). Therefore, each parent contributes half the genetic information carried by the offspring; the
resulting physical characteristics of the offspring (called the phenotype) are determined by the interaction
of genetic material supplied by the parents (called the genotype). A person’s genotype is the genetic
makeup of that individual. Phenotype, on the other hand, refers to the individual’s inherited physical
characteristics, which are a combination of genetic and environmental influences (Figure 3.4).

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Figure 3.4 (a) Genotype refers to the genetic makeup of an individual based on the genetic material (DNA) inherited
from one’s parents. (b) Phenotype describes an individual’s observable characteristics, such as hair color, skin color,
height, and build. (credit a: modification of work by Caroline Davis; credit b: modification of work by Cory Zanker)

Most traits are controlled by multiple genes, but some traits are controlled by one gene. A characteristic
like cleft chin, for example, is influenced by a single gene from each parent. In this example, we will call
the gene for cleft chin “B,” and the gene for smooth chin “b.” Cleft chin is a dominant trait, which means
that having the dominant allele either from one parent (Bb) or both parents (BB) will always result in the
phenotype associated with the dominant allele. When someone has two copies of the same allele, they are
said to be homozygous for that allele. When someone has a combination of alleles for a given gene, they
are said to be heterozygous. For example, smooth chin is a recessive trait, which means that an individual
will only display the smooth chin phenotype if they are homozygous for that recessive allele (bb).

Imagine that a woman with a cleft chin mates with a man with a smooth chin. What type of chin will their
child have? The answer to that depends on which alleles each parent carries. If the woman is homozygous
for cleft chin (BB), her offspring will always have cleft chin. It gets a little more complicated, however, if
the mother is heterozygous for this gene (Bb). Since the father has a smooth chin—therefore homozygous
for the recessive allele (bb)—we can expect the offspring to have a 50% chance of having a cleft chin and a
50% chance of having a smooth chin (Figure 3.5).

Figure 3.5 (a) A Punnett square is a tool used to predict how genes will interact in the production of offspring. The
capital B represents the dominant allele, and the lowercase b represents the recessive allele. In the example of the
cleft chin, where B is cleft chin (dominant allele), wherever a pair contains the dominant allele, B, you can expect a
cleft chin phenotype. You can expect a smooth chin phenotype only when there are two copies of the recessive allele,
bb. (b) A cleft chin, shown here, is an inherited trait.

In sickle cell anemia, heterozygous carriers (like Luwi from the example) can develop blood resistance to
malaria infection while those who are homozygous (like Sena) have a potentially lethal blood disorder.
Sickle-cell anemia is just one of many genetic disorders caused by the pairing of two recessive genes.
For example, phenylketonuria (PKU) is a condition in which individuals lack an enzyme that normally

Chapter 3 | Biopsychology 79

converts harmful amino acids into harmless byproducts. If someone with this condition goes untreated, he
or she will experience significant deficits in cognitive function, seizures, and an increased risk of various
psychiatric disorders. Because PKU is a recessive trait, each parent must have at least one copy of the
recessive allele in order to produce a child with the condition (Figure 3.6).

So far, we have discussed traits that involve just one gene, but few human characteristics are controlled
by a single gene. Most traits are polygenic: controlled by more than one gene. Height is one example of a
polygenic trait, as are skin color and weight.

Figure 3.6 In this Punnett square, N represents the normal allele, and p represents the recessive allele that is
associated with PKU. If two individuals mate who are both heterozygous for the allele associated with PKU, their
offspring have a 25% chance of expressing the PKU phenotype.

Where do harmful genes that contribute to diseases like PKU come from? Gene mutations provide one
source of harmful genes. A mutation is a sudden, permanent change in a gene. While many mutations can
be harmful or lethal, once in a while, a mutation benefits an individual by giving that person an advantage
over those who do not have the mutation. Recall that the theory of evolution asserts that individuals best
adapted to their particular environments are more likely to reproduce and pass on their genes to future
generations. In order for this process to occur, there must be competition—more technically, there must
be variability in genes (and resultant traits) that allow for variation in adaptability to the environment.
If a population consisted of identical individuals, then any dramatic changes in the environment would
affect everyone in the same way, and there would be no variation in selection. In contrast, diversity in
genes and associated traits allows some individuals to perform slightly better than others when faced with
environmental change. This creates a distinct advantage for individuals best suited for their environments
in terms of successful reproduction and genetic transmission.

Human Diversity

This chapter focuses on biology. Later in this course you will learn about social psychology and issues of race,
prejudice, and discrimination. When we focus strictly on biology, race becomes a weak construct. After the

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sequencing of the human genome at the turn of the millennium, many scientists began to argue that race was
not a useful variable in genetic research and that its continued use represents a potential source of confusion
and harm. The racial categories that some believed to be helpful in studying genetic diversity in humans are
largely irrelevant. A person’s skin tone, eye color, and hair texture are functions of their genetic makeups, but
there is actually more genetic variation within a given racial category than there is between racial categories.
In some cases, focus on race has led to difficulties with misdiagnoses and/or under-diagnoses of diseases
ranging from sickle cell anemia to cystic fibrosis. Some argue that we need to distinguish between ancestry
and race and then focus on ancestry. This approach would facilitate greater understanding of human genetic
diversity (Yudell, Roberts, DeSalle, & Tishkoff, 2016).

GENE-ENVIRONMENT INTERACTIONS

Genes do not exist in a vacuum. Although we are all biological organisms, we also exist in an environment
that is incredibly important in determining not only when and how our genes express themselves, but
also in what combination. Each of us represents a unique interaction between our genetic makeup and our
environment; range of reaction is one way to describe this interaction. Range of reaction asserts that our
genes set the boundaries within which we can operate, and our environment interacts with the genes to
determine where in that range we will fall. For example, if an individual’s genetic makeup predisposes
her to high levels of intellectual potential and she is reared in a rich, stimulating environment, then she
will be more likely to achieve her full potential than if she were raised under conditions of significant
deprivation. According to the concept of range of reaction, genes set definite limits on potential, and
environment determines how much of that potential is achieved. Some disagree with this theory and
argue that genes do not set a limit on a person’s potential with reaction norms being determined by
the environment. For example, when individuals experience neglect or abuse early in life, they are more
likely to exhibit adverse psychological and/or physical conditions that can last throughout their lives.
These conditions may develop as a function of the negative environmental experiences in individuals from
dissimilar genetic backgrounds (Miguel, Pereira, Silveira, & Meaney, 2019; Short & Baram, 2019).

Another perspective on the interaction between genes and the environment is the concept of genetic
environmental correlation. Stated simply, our genes influence our environment, and our environment
influences the expression of our genes (Figure 3.7). Not only do our genes and environment interact,
as in range of reaction, but they also influence one another bidirectionally. For example, the child of an
NBA player would probably be exposed to basketball from an early age. Such exposure might allow the
child to realize his or her full genetic, athletic potential. Thus, the parents’ genes, which the child shares,
influence the child’s environment, and that environment, in turn, is well suited to support the child’s
genetic potential.

Chapter 3 | Biopsychology 81

Figure 3.7 Nature and nurture work together like complex pieces of a human puzzle. The interaction of our
environment and genes makes us the individuals we are. (credit “puzzle”: modification of work by Cory Zanker; credit
“houses”: modification of work by Ben Salter; credit “DNA”: modification of work by NHGRI)

In another approach to gene-environment interactions, the field of epigenetics looks beyond the genotype
itself and studies how the same genotype can be expressed in different ways. In other words, researchers
study how the same genotype can lead to very different phenotypes. As mentioned earlier, gene
expression is often influenced by environmental context in ways that are not entirely obvious. For instance,
identical twins share the same genetic information (identical twins develop from a single fertilized egg
that split, so the genetic material is exactly the same in each; in contrast, fraternal twins usually result from
two different eggs fertilized by different sperm, so the genetic material varies as with non-twin siblings).
But even with identical genes, there remains an incredible amount of variability in how gene expression
can unfold over the course of each twin’s life. Sometimes, one twin will develop a disease and the other
will not. In one example, Aliya, an identical twin, died from cancer at age 7, but her twin, now 19 years
old, has never had cancer. Although these individuals share an identical genotype, their phenotypes differ
as a result of how that genetic information is expressed over time and through their unique environmental
interactions. The epigenetic perspective is very different from range of reaction, because here the genotype
is not fixed and limited.

Watch this video about the epigenetics of twin studies (http://openstax.org/l/twinstudy) to learn
more.

Genes affect more than our physical characteristics. Indeed, scientists have found genetic linkages to
a number of behavioral characteristics, ranging from basic personality traits to sexual orientation to
spirituality (for examples, see Mustanski et al., 2005; Comings, Gonzales, Saucier, Johnson, & MacMurray,
2000). Genes are also associated with temperament and a number of psychological disorders, such as
depression and schizophrenia. So while it is true that genes provide the biological blueprints for our cells,
tissues, organs, and body, they also have a significant impact on our experiences and our behaviors.

Let’s look at the following findings regarding schizophrenia in light of our three views of gene-
environment interactions. Which view do you think best explains this evidence?

In a 2004 study by Tienari and colleagues, of people who were given up for adoption, adoptees whose
biological mothers had schizophrenia and who had been raised in a disturbed family environment were
much more likely to develop schizophrenia or another psychotic disorder than were any of the other

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groups in the study:

• Of adoptees whose biological mothers had schizophrenia (high genetic risk) and who were raised
in disturbed family environments, 36.8% were likely to develop schizophrenia.

• Of adoptees whose biological mothers had schizophrenia (high genetic risk) and who were raised
in healthy family environments, 5.8% were likely to develop schizophrenia.

• Of adoptees with a low genetic risk (whose mothers did not have schizophrenia) and who were
raised in disturbed family environments, 5.3% were likely to develop schizophrenia.

• Of adoptees with a low genetic risk (whose mothers did not have schizophrenia) and who were
raised in healthy family environments, 4.8% were likely to develop schizophrenia.

The study shows that adoptees with high genetic risk were most likely to develop schizophrenia if they
were raised in disturbed home environments. This research lends credibility to the notion that both genetic
vulnerability and environmental stress are necessary for schizophrenia to develop, and that genes alone
do not tell the full tale.

3.2 Cells of the Nervous System

Learning Objectives

By the end of this section, you will be able to:
• Identify the basic parts of a neuron
• Describe how neurons communicate with each other
• Explain how drugs act as agonists or antagonists for a given neurotransmitter system

Psychologists striving to understand the human mind may study the nervous system. Learning how the
body’s cells and organs function can help us understand the biological basis of human psychology. The
nervous system is composed of two basic cell types: glial cells (also known as glia) and neurons. Glial
cells are traditionally thought to play a supportive role to neurons, both physically and metabolically.
Glial cells provide scaffolding on which the nervous system is built, help neurons line up closely with
each other to allow neuronal communication, provide insulation to neurons, transport nutrients and waste
products, and mediate immune responses. For years, researchers believed that there were many more glial
cells than neurons; however, more recent work from Suzanna Herculano-Houzel’s laboratory has called
this long-standing assumption into question and has provided important evidence that there may be a
nearly 1:1 ratio of glia cells to neurons. This is important because it suggests that human brains are more
similar to other primate brains than previously thought (Azevedo et al, 2009; Hercaulano-Houzel, 2012;
Herculano-Houzel, 2009). Neurons, on the other hand, serve as interconnected information processors that
are essential for all of the tasks of the nervous system. This section briefly describes the structure and
function of neurons.

NEURON STRUCTURE

Neurons are the central building blocks of the nervous system, 100 billion strong at birth. Like all cells,
neurons consist of several different parts, each serving a specialized function (Figure 3.8). A neuron’s
outer surface is made up of a semipermeable membrane. This membrane allows smaller molecules
and molecules without an electrical charge to pass through it, while stopping larger or highly charged
molecules.

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Figure 3.8 This illustration shows a prototypical neuron, which is being myelinated by a glial cell.

The nucleus of the neuron is located in the soma, or cell body. The soma has branching extensions known
as dendrites. The neuron is a small information processor, and dendrites serve as input sites where signals
are received from other neurons. These signals are transmitted electrically across the soma and down a
major extension from the soma known as the axon, which ends at multiple terminal buttons. The terminal
buttons contain synaptic vesicles that house neurotransmitters, the chemical messengers of the nervous
system.

Axons range in length from a fraction of an inch to several feet. In some axons, glial cells form a fatty
substance known as the myelin sheath, which coats the axon and acts as an insulator, increasing the
speed at which the signal travels. The myelin sheath is not continuous and there are small gaps that
occur down the length of the axon. These gaps in the myelin sheath are known as the Nodes of Ranvier.
The myelin sheath is crucial for the normal operation of the neurons within the nervous system: the
loss of the insulation it provides can be detrimental to normal function. To understand how this works,
let’s consider an example. PKU, a genetic disorder discussed earlier, causes a reduction in myelin and
abnormalities in white matter cortical and subcortical structures. The disorder is associated with a variety
of issues including severe cognitive deficits, exaggerated reflexes, and seizures (Anderson & Leuzzi, 2010;
Huttenlocher, 2000). Another disorder, multiple sclerosis (MS), an autoimmune disorder, involves a large-
scale loss of the myelin sheath on axons throughout the nervous system. The resulting interference in
the electrical signal prevents the quick transmittal of information by neurons and can lead to a number
of symptoms, such as dizziness, fatigue, loss of motor control, and sexual dysfunction. While some
treatments may help to modify the course of the disease and manage certain symptoms, there is currently
no known cure for multiple sclerosis.

In healthy individuals, the neuronal signal moves rapidly down the axon to the terminal buttons, where
synaptic vesicles release neurotransmitters into the synaptic cleft (Figure 3.9). The synaptic cleft is a
very small space between two neurons and is an important site where communication between neurons
occurs. Once neurotransmitters are released into the synaptic cleft, they travel across it and bind with
corresponding receptors on the dendrite of an adjacent neuron. Receptors, proteins on the cell surface
where neurotransmitters attach, vary in shape, with different shapes “matching” different
neurotransmitters.

How does a neurotransmitter “know” which receptor to bind to? The neurotransmitter and the receptor
have what is referred to as a lock-and-key relationship—specific neurotransmitters fit specific receptors
similar to how a key fits a lock. The neurotransmitter binds to any receptor that it fits.

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Figure 3.9 (a) The synaptic cleft is the space between the terminal button of one neuron and the dendrite of another
neuron. (b) In this pseudo-colored image from a scanning electron microscope, a terminal button (green) has been
opened to reveal the synaptic vesicles (orange and blue) inside. Each vesicle contains about 10,000 neurotransmitter
molecules. (credit b: modification of work by Tina Carvalho, NIH-NIGMS; scale-bar data from Matt Russell)

NEURONAL COMMUNICATION

Now that we have learned about the basic structures of the neuron and the role that these structures play
in neuronal communication, let’s take a closer look at the signal itself—how it moves through the neuron
and then jumps to the next neuron, where the process is repeated.

We begin at the neuronal membrane. The neuron exists in a fluid environment—it is surrounded by
extracellular fluid and contains intracellular fluid (i.e., cytoplasm). The neuronal membrane keeps these
two fluids separate—a critical role because the electrical signal that passes through the neuron depends
on the intra- and extracellular fluids being electrically different. This difference in charge across the
membrane, called the membrane potential, provides energy for the signal.

The electrical charge of the fluids is caused by charged molecules (ions) dissolved in the fluid. The
semipermeable nature of the neuronal membrane somewhat restricts the movement of these charged
molecules, and, as a result, some of the charged particles tend to become more concentrated either inside
or outside the cell.

Between signals, the neuron membrane’s potential is held in a state of readiness, called the resting
potential. Like a rubber band stretched out and waiting to spring into action, ions line up on either side
of the cell membrane, ready to rush across the membrane when the neuron goes active and the membrane
opens its gates (i.e., a sodium-potassium pump that allows movement of ions across the membrane). Ions
in high-concentration areas are ready to move to low-concentration areas, and positive ions are ready to
move to areas with a negative charge.

In the resting state, sodium (Na+) is at higher concentrations outside the cell, so it will tend to move into
the cell. Potassium (K+), on the other hand, is more concentrated inside the cell, and will tend to move out
of the cell (Figure 3.10). In addition, the inside of the cell is slightly negatively charged compared to the
outside. This provides an additional force on sodium, causing it to move into the cell.

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Figure 3.10 At resting potential, Na+ (blue pentagons) is more highly concentrated outside the cell in the
extracellular fluid (shown in blue), whereas K+ (purple squares) is more highly concentrated near the membrane in
the cytoplasm or intracellular fluid. Other molecules, such as chloride ions (yellow circles) and negatively charged
proteins (brown squares), help contribute to a positive net charge in the extracellular fluid and a negative net charge
in the intracellular fluid.

From this resting potential state, the neuron receives a signal and its state changes abruptly (Figure
3.11). When a neuron receives signals at the dendrites—due to neurotransmitters from an adjacent neuron
binding to its receptors—small pores, or gates, open on the neuronal membrane, allowing Na+ ions,
propelled by both charge and concentration differences, to move into the cell. With this influx of positive
ions, the internal charge of the cell becomes more positive. If that charge reaches a certain level, called the
threshold of excitation, the neuron becomes active and the action potential begins.

Many additional pores open, causing a massive influx of Na+ ions and a huge positive spike in the
membrane potential, the peak action potential. At the peak of the spike, the sodium gates close and the
potassium gates open. As positively charged potassium ions leave, the cell quickly begins repolarization.
At first, it hyperpolarizes, becoming slightly more negative than the resting potential, and then it levels
off, returning to the resting potential.

Figure 3.11 During the action potential, the electrical charge across the membrane changes dramatically.

This positive spike constitutes the action potential: the electrical signal that typically moves from the cell
body down the axon to the axon terminals. The electrical signal moves down the axon with the impulses
jumping in a leapfrog fashion between the Nodes of Ranvier. The Nodes of Ranvier are natural gaps in the
myelin sheath. At each point, some of the sodium ions that enter the cell diffuse to the next section of the

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axon, raising the charge past the threshold of excitation and triggering a new influx of sodium ions. The
action potential moves all the way down the axon in this fashion until reaching the terminal buttons.

The action potential is an all-or-none phenomenon. In simple terms, this means that an incoming signal
from another neuron is either sufficient or insufficient to reach the threshold of excitation. There is no in-
between, and there is no turning off an action potential once it starts. Think of it like sending an email or
a text message. You can think about sending it all you want, but the message is not sent until you hit the
send button. Furthermore, once you send the message, there is no stopping it.

Because it is all or none, the action potential is recreated, or propagated, at its full strength at every point
along the axon. Much like the lit fuse of a firecracker, it does not fade away as it travels down the axon. It
is this all-or-none property that explains the fact that your brain perceives an injury to a distant body part
like your toe as equally painful as one to your nose.

As noted earlier, when the action potential arrives at the terminal button, the synaptic vesicles release
their neurotransmitters into the synaptic cleft. The neurotransmitters travel across the synapse and bind
to receptors on the dendrites of the adjacent neuron, and the process repeats itself in the new neuron
(assuming the signal is sufficiently strong to trigger an action potential). Once the signal is delivered,
excess neurotransmitters in the synaptic cleft drift away, are broken down into inactive fragments, or
are reabsorbed in a process known as reuptake. Reuptake involves the neurotransmitter being pumped
back into the neuron that released it, in order to clear the synapse (Figure 3.12). Clearing the synapse
serves both to provide a clear “on” and “off” state between signals and to regulate the production of
neurotransmitter (full synaptic vesicles provide signals that no additional neurotransmitters need to be
produced).

Figure 3.12 Reuptake involves moving a neurotransmitter from the synapse back into the axon terminal from which
it was released.

Neuronal communication is often referred to as an electrochemical event. The movement of the action
potential down the length of the axon is an electrical event, and movement of the neurotransmitter across
the synaptic space represents the chemical portion of the process. However, there are some specialized
connections between neurons that are entirely electrical. In such cases, the neurons are said to
communicate via an electrical synapse. In these cases, two neurons physically connect to one another via
gap junctions, which allows the current from one cell to pass into the next. There are far fewer electrical
synapses in the brain, but those that do exist are much faster than the chemical synapses that have been
described above (Connors & Long, 2004).

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Watch this video about neuronal communication (http://openstax.org/l/neuroncom) to learn more.

NEUROTRANSMITTERS AND DRUGS

There are several different types of neurotransmitters released by different neurons, and we can speak in
broad terms about the kinds of functions associated with different neurotransmitters (Table 3.1). Much
of what psychologists know about the functions of neurotransmitters comes from research on the effects
of drugs in psychological disorders. Psychologists who take a biological perspective and focus on the
physiological causes of behavior assert that psychological disorders like depression and schizophrenia are
associated with imbalances in one or more neurotransmitter systems. In this perspective, psychotropic
medications can help improve the symptoms associated with these disorders. Psychotropic medications
are drugs that treat psychiatric symptoms by restoring neurotransmitter balance.

Major Neurotransmitters and How They Affect Behavior

Neurotransmitter Involved in Potential Effect on Behavior

Acetylcholine Muscle action, memory Increased arousal, enhanced
cognition

Beta-endorphin Pain, pleasure Decreased anxiety, decreased
tension

Dopamine Mood, sleep, learning Increased pleasure, suppressed
appetite

Gamma-aminobutyric acid
(GABA)

Brain function, sleep Decreased anxiety, decreased
tension

Glutamate Memory, learning Increased learning, enhanced
memory

Norepinephrine Heart, intestines,
alertness

Increased arousal, suppressed
appetite

Serotonin Mood, sleep Modulated mood, suppressed
appetite

Table 3.1

Psychoactive drugs can act as agonists or antagonists for a given neurotransmitter system. Agonists
are chemicals that mimic a neurotransmitter at the receptor site. An antagonist, on the other hand,
blocks or impedes the normal activity of a neurotransmitter at the receptor. Agonists and antagonists
represent drugs that are prescribed to correct the specific neurotransmitter imbalances underlying a
person’s condition. For example, Parkinson’s disease, a progressive nervous system disorder, is associated
with low levels of dopamine. Therefore, a common treatment strategy for Parkinson’s disease involves
using dopamine agonists, which mimic the effects of dopamine by binding to dopamine receptors.

Certain symptoms of schizophrenia are associated with overactive dopamine neurotransmission. The

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antipsychotics used to treat these symptoms are antagonists for dopamine—they block dopamine’s effects
by binding its receptors without activating them. Thus, they prevent dopamine released by one neuron
from signaling information to adjacent neurons.

In contrast to agonists and antagonists, which both operate by binding to receptor sites, reuptake inhibitors
prevent unused neurotransmitters from being transported back to the neuron. This allows
neurotransmitters to remain active in the synaptic cleft for longer durations, increasing their effectiveness.
Depression, which has been consistently linked with reduced serotonin levels, is commonly treated with
selective serotonin reuptake inhibitors (SSRIs). By preventing reuptake, SSRIs strengthen the effect of
serotonin, giving it more time to interact with serotonin receptors on dendrites. Common SSRIs on the
market today include Prozac, Paxil, and Zoloft. The drug LSD is structurally very similar to serotonin,
and it affects the same neurons and receptors as serotonin. Psychotropic drugs are not instant solutions
for people suffering from psychological disorders. Often, an individual must take a drug for several
weeks before seeing improvement, and many psychoactive drugs have significant negative side effects.
Furthermore, individuals vary dramatically in how they respond to the drugs. To improve chances for
success, it is not uncommon for people receiving pharmacotherapy to undergo psychological and/or
behavioral therapies as well. Some research suggests that combining drug therapy with other forms of
therapy tends to be more effective than any one treatment alone (for one such example, see March et al.,
2007).

3.3 Parts of the Nervous System

Learning Objectives

By the end of this section, you will be able to:
• Describe the difference between the central and peripheral nervous systems
• Explain the difference between the somatic and autonomic nervous systems
• Differentiate between the sympathetic and parasympathetic divisions of the autonomic

nervous system

The nervous system can be divided into two major subdivisions: the central nervous system (CNS) and
the peripheral nervous system (PNS), shown in Figure 3.13. The CNS is comprised of the brain and spinal
cord; the PNS connects the CNS to the rest of the body. In this section, we focus on the peripheral nervous
system; later, we look at the brain and spinal cord.

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Figure 3.13 The nervous system is divided into two major parts: (a) the Central Nervous System and (b) the
Peripheral Nervous System.

PERIPHERAL NERVOUS SYSTEM

The peripheral nervous system is made up of thick bundles of axons, called nerves, carrying messages
back and forth between the CNS and the muscles, organs, and senses in the periphery of the body (i.e.,
everything outside the CNS). The PNS has two major subdivisions: the somatic nervous system and the
autonomic nervous system.

The somatic nervous system is associated with activities traditionally thought of as conscious or
voluntary. It is involved in the relay of sensory and motor information to and from the CNS; therefore,
it consists of motor neurons and sensory neurons. Motor neurons, carrying instructions from the CNS to
the muscles, are efferent fibers (efferent means “moving away from”). Sensory neurons, carrying sensory
information to the CNS, are afferent fibers (afferent means “moving toward”). A helpful way to remember
this is that efferent = exit and afferent = arrive. Each nerve is basically a bundle of neurons forming a two-
way superhighway, containing thousands of axons, both efferent and afferent.

The autonomic nervous system controls our internal organs and glands and is generally considered
to be outside the realm of voluntary control. It can be further subdivided into the sympathetic and
parasympathetic divisions (Figure 3.14). The sympathetic nervous system is involved in preparing the
body for stress-related activities; the parasympathetic nervous system is associated with returning the
body to routine, day-to-day operations. The two systems have complementary functions, operating in
tandem to maintain the body’s homeostasis. Homeostasis is a state of equilibrium, or balance, in which
biological conditions (such as body temperature) are maintained at optimal levels.

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Figure 3.14 The sympathetic and parasympathetic divisions of the autonomic nervous system have the opposite
effects on various systems.

The sympathetic nervous system is activated when we are faced with stressful or high-arousal situations.
The activity of this system was adaptive for our ancestors, increasing their chances of survival. Imagine,
for example, that one of our early ancestors, out hunting small game, suddenly disturbs a large bear
with her cubs. At that moment, his body undergoes a series of changes—a direct function of sympathetic
activation—preparing him to face the threat. His pupils dilate, his heart rate and blood pressure increase,
his bladder relaxes, his liver releases glucose, and adrenaline surges into his bloodstream. This
constellation of physiological changes, known as the fight or flight response, allows the body access to
energy reserves and heightened sensory capacity so that it might fight off a threat or run away to safety.

Watch this video about the Fight Flight Freeze response (http://openstax.org/l/response) to learn
more.

While it is clear that such a response would be critical for survival for our ancestors, who lived in a world
full of real physical threats, many of the high-arousal situations we face in the modern world are more
psychological in nature. For example, think about how you feel when you have to stand up and give a
presentation in front of a roomful of people, or right before taking a big test. You are in no real physical
danger in those situations, and yet you have evolved to respond to a perceived threat with the fight or
flight response. This kind of response is not nearly as adaptive in the modern world; in fact, we suffer

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negative health consequences when faced constantly with psychological threats that we can neither fight
nor flee. Recent research suggests that an increase in susceptibility to heart disease (Chandola, Brunner,
& Marmot, 2006) and impaired function of the immune system (Glaser & Kiecolt-Glaser, 2005) are among
the many negative consequences of persistent and repeated exposure to stressful situations. Some of this
tendency for stress reactivity can be wired by early experiences of trauma.

Once the threat has been resolved, the parasympathetic nervous system takes over and returns bodily
functions to a relaxed state. Our hunter’s heart rate and blood pressure return to normal, his pupils
constrict, he regains control of his bladder, and the liver begins to store glucose in the form of glycogen
for future use. These restorative processes are associated with activation of the parasympathetic nervous
system.

3.4 The Brain and Spinal Cord

Learning Objectives

By the end of this section, you will be able to:
• Explain the functions of the spinal cord
• Identify the hemispheres and lobes of the brain
• Describe the types of techniques available to clinicians and researchers to image or scan the

brain

The brain is a remarkably complex organ comprised of billions of interconnected neurons and glia. It is
a bilateral, or two-sided, structure that can be separated into distinct lobes. Each lobe is associated with
certain types of functions, but, ultimately, all of the areas of the brain interact with one another to provide
the foundation for our thoughts and behaviors. In this section, we discuss the overall organization of
the brain and the functions associated with different brain areas, beginning with what can be seen as an
extension of the brain, the spinal cord.

THE SPINAL CORD

It can be said that the spinal cord is what connects the brain to the outside world. Because of it, the brain
can act. The spinal cord is like a relay station, but a very smart one. It not only routes messages to and from
the brain, but it also has its own system of automatic processes, called reflexes.

The top of the spinal cord is a bundle of nerves that merges with the brain stem, where the basic processes
of life are controlled, such as breathing and digestion. In the opposite direction, the spinal cord ends just
below the ribs—contrary to what we might expect, it does not extend all the way to the base of the spine.

The spinal cord is functionally organized in 30 segments, corresponding with the vertebrae. Each segment
is connected to a specific part of the body through the peripheral nervous system. Nerves branch out
from the spine at each vertebra. Sensory nerves bring messages in; motor nerves send messages out to the
muscles and organs. Messages travel to and from the brain through every segment.

Some sensory messages are immediately acted on by the spinal cord, without any input from the brain.
Withdrawal from a hot object and the knee jerk are two examples. When a sensory message meets certain
parameters, the spinal cord initiates an automatic reflex. The signal passes from the sensory nerve to a
simple processing center, which initiates a motor command. Seconds are saved, because messages don’t
have to go the brain, be processed, and get sent back. In matters of survival, the spinal reflexes allow the
body to react extraordinarily fast.

The spinal cord is protected by bony vertebrae and cushioned in cerebrospinal fluid, but injuries still
occur. When the spinal cord is damaged in a particular segment, all lower segments are cut off from the
brain, causing paralysis. Therefore, the lower on the spine damage occurs, the fewer functions an injured

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individual will lose.

Neuroplasticity

Bob Woodruff, a reporter for ABC, suffered a traumatic brain injury after a bomb exploded next to the
vehicle he was in while covering a news story in Iraq. As a consequence of these injuries, Woodruff
experienced many cognitive deficits including difficulties with memory and language. However, over time
and with the aid of intensive amounts of cognitive and speech therapy, Woodruff has shown an incredible
recovery of function (Fernandez, 2008, October 16).

One of the factors that made this recovery possible was neuroplasticity. Neuroplasticity refers to how the
nervous system can change and adapt. Neuroplasticity can occur in a variety of ways including personal
experiences, developmental processes, or, as in Woodruff’s case, in response to some sort of damage or
injury that has occurred. Neuroplasticity can involve creation of new synapses, pruning of synapses that
are no longer used, changes in glial cells, and even the birth of new neurons. Because of neuroplasticity,
our brains are constantly changing and adapting, and while our nervous system is most plastic when we
are very young, as Woodruff’s case suggests, it is still capable of remarkable changes later in life.

THE TWO HEMISPHERES

The surface of the brain, known as the cerebral cortex, is very uneven, characterized by a distinctive
pattern of folds or bumps, known as gyri (singular: gyrus), and grooves, known as sulci (singular: sulcus),
shown in Figure 3.15. These gyri and sulci form important landmarks that allow us to separate the brain
into functional centers. The most prominent sulcus, known as the longitudinal fissure, is the deep groove
that separates the brain into two halves or hemispheres: the left hemisphere and the right hemisphere.

Figure 3.15 The surface of the brain is covered with gyri and sulci. A deep sulcus is called a fissure, such as the
longitudinal fissure that divides the brain into left and right hemispheres. (credit: modification of work by Bruce Blaus)

There is evidence of specialization of function—referred to as lateralization—in each hemisphere, mainly
regarding differences in language functions. The left hemisphere controls the right half of the body,
and the right hemisphere controls the left half of the body. Decades of research on lateralization of
function by Michael Gazzaniga and his colleagues suggest that a variety of functions ranging from cause-
and-effect reasoning to self-recognition may follow patterns that suggest some degree of hemispheric
dominance (Gazzaniga, 2005). For example, the left hemisphere has been shown to be superior for forming
associations in memory, selective attention, and positive emotions. The right hemisphere, on the other
hand, has been shown to be superior in pitch perception, arousal, and negative emotions (Ehret, 2006).
However, it should be pointed out that research on which hemisphere is dominant in a variety of different
behaviors has produced inconsistent results, and therefore, it is probably better to think of how the
two hemispheres interact to produce a given behavior rather than attributing certain behaviors to one

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hemisphere versus the other (Banich & Heller, 1998).

The two hemispheres are connected by a thick band of neural fibers known as the corpus callosum,
consisting of about 200 million axons. The corpus callosum allows the two hemispheres to communicate
with each other and allows for information being processed on one side of the brain to be shared with the
other side.

Normally, we are not aware of the different roles that our two hemispheres play in day-to-day functions,
but there are people who come to know the capabilities and functions of their two hemispheres quite well.
In some cases of severe epilepsy, doctors elect to sever the corpus callosum as a means of controlling the
spread of seizures (Figure 3.16). While this is an effective treatment option, it results in individuals who
have “split brains.” After surgery, these split-brain patients show a variety of interesting behaviors. For
instance, a split-brain patient is unable to name a picture that is shown in the patient’s left visual field
because the information is only available in the largely nonverbal right hemisphere. However, they are
able to recreate the picture with their left hand, which is also controlled by the right hemisphere. When the
more verbal left hemisphere sees the picture that the hand drew, the patient is able to name it (assuming
the left hemisphere can interpret what was drawn by the left hand).

Figure 3.16 (a, b) The corpus callosum connects the left and right hemispheres of the brain. (c) A scientist spreads
this dissected sheep brain apart to show the corpus callosum between the hemispheres. (credit c: modification of
work by Aaron Bornstein)

Much of what we know about the functions of different areas of the brain comes from studying changes in
the behavior and ability of individuals who have suffered damage to the brain. For example, researchers
study the behavioral changes caused by strokes to learn about the functions of specific brain areas. A
stroke, caused by an interruption of blood flow to a region in the brain, causes a loss of brain function in
the affected region. The damage can be in a small area, and, if it is, this gives researchers the opportunity
to link any resulting behavioral changes to a specific area. The types of deficits displayed after a stroke will
be largely dependent on where in the brain the damage occurred.

Consider Theona, an intelligent, self-sufficient woman, who is 62 years old. Recently, she suffered a stroke
in the front portion of her right hemisphere. As a result, she has great difficulty moving her left leg. (As you
learned earlier, the right hemisphere controls the left side of the body; also, the brain’s main motor centers
are located at the front of the head, in the frontal lobe.) Theona has also experienced behavioral changes.
For example, while in the produce section of the grocery store, she sometimes eats grapes, strawberries,
and apples directly from their bins before paying for them. This behavior—which would have been very
embarrassing to her before the stroke—is consistent with damage in another region in the frontal lobe—the
prefrontal cortex, which is associated with judgment, reasoning, and impulse control.

FOREBRAIN STRUCTURES

The two hemispheres of the cerebral cortex are part of the forebrain (Figure 3.17), which is the largest part
of the brain. The forebrain contains the cerebral cortex and a number of other structures that lie beneath
the cortex (called subcortical structures): thalamus, hypothalamus, pituitary gland, and the limbic system

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(a collection of structures). The cerebral cortex, which is the outer surface of the brain, is associated with
higher level processes such as consciousness, thought, emotion, reasoning, language, and memory. Each
cerebral hemisphere can be subdivided into four lobes, each associated with different functions.

Figure 3.17 The brain and its parts can be divided into three main categories: the forebrain, midbrain, and hindbrain.

Lobes of the Brain

The four lobes of the brain are the frontal, parietal, temporal, and occipital lobes (Figure 3.18). The frontal
lobe is located in the forward part of the brain, extending back to a fissure known as the central sulcus. The
frontal lobe is involved in reasoning, motor control, emotion, and language. It contains the motor cortex,
which is involved in planning and coordinating movement; the prefrontal cortex, which is responsible for
higher-level cognitive functioning; and Broca’s area, which is essential for language production.

Figure 3.18 The lobes of the brain are shown.

People who suffer damage to Broca’s area have great difficulty producing language of any form (Figure
3.18). For example, Padma was an electrical engineer who was socially active and a caring, involved
parent. About twenty years ago, she was in a car accident and suffered damage to her Broca’s area. She
completely lost the ability to speak and form any kind of meaningful language. There is nothing wrong
with her mouth or her vocal cords, but she is unable to produce words. She can follow directions but can’t
respond verbally, and she can read but no longer write. She can do routine tasks like running to the market
to buy milk, but she could not communicate verbally if a situation called for it.

Probably the most famous case of frontal lobe damage is that of a man by the name of Phineas Gage. On
September 13, 1848, Gage (age 25) was working as a railroad foreman in Vermont. He and his crew were

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using an iron rod to tamp explosives down into a blasting hole to remove rock along the railway’s path.
Unfortunately, the iron rod created a spark and caused the rod to explode out of the blasting hole, into
Gage’s face, and through his skull (Figure 3.19). Although lying in a pool of his own blood with brain
matter emerging from his head, Gage was conscious and able to get up, walk, and speak. But in the months
following his accident, people noticed that his personality had changed. Many of his friends described him
as no longer being himself. Before the accident, it was said that Gage was a well-mannered, soft-spoken
man, but he began to behave in odd and inappropriate ways after the accident. Such changes in personality
would be consistent with loss of impulse control—a frontal lobe function.

Beyond the damage to the frontal lobe itself, subsequent investigations into the rod’s path also identified
probable damage to pathways between the frontal lobe and other brain structures, including the limbic
system. With connections between the planning functions of the frontal lobe and the emotional processes
of the limbic system severed, Gage had difficulty controlling his emotional impulses.

However, there is some evidence suggesting that the dramatic changes in Gage’s personality were
exaggerated and embellished. Gage’s case occurred in the midst of a 19th century debate over
localization—regarding whether certain areas of the brain are associated with particular functions. On the
basis of extremely limited information about Gage, the extent of his injury, and his life before and after the
accident, scientists tended to find support for their own views, on whichever side of the debate they fell
(Macmillan, 1999).

Figure 3.19 (a) Phineas Gage holds the iron rod that penetrated his skull in an 1848 railroad construction accident.
(b) Gage’s prefrontal cortex was severely damaged in the left hemisphere. The rod entered Gage’s face on the left
side, passed behind his eye, and exited through the top of his skull, before landing about 80 feet away. (credit a:
modification of work by Jack and Beverly Wilgus)

The brain’s parietal lobe is located immediately behind the frontal lobe, and is involved in processing
information from the body’s senses. It contains the somatosensory cortex, which is essential for processing
sensory information from across the body, such as touch, temperature, and pain. The somatosensory cortex
is organized topographically, which means that spatial relationships that exist in the body are generally
maintained on the surface of the somatosensory cortex (Figure 3.20). For example, the portion of the cortex
that processes sensory information from the hand is adjacent to the portion that processes information
from the wrist.

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One fascinating example of neuroplasticity involves reorganization of the somatosensory cortex following
limb amputation. Check out this NPR segment about amputees’ experiences of “phantom limbs”
following amputation (http://openstax.org/l/phantomlimb) to learn more.

Figure 3.20 Spatial relationships in the body are mirrored in the organization of the somatosensory cortex.

The temporal lobe is located on the side of the head (temporal means “near the temples”), and is associated
with hearing, memory, emotion, and some aspects of language. The auditory cortex, the main area
responsible for processing auditory information, is located within the temporal lobe. Wernicke’s area,
important for speech comprehension, is also located here. Whereas individuals with damage to Broca’s
area have difficulty producing language, those with damage to Wernicke’s area can produce sensible
language, but they are unable to understand it (Figure 3.21).

Figure 3.21 Damage to either Broca’s area or Wernicke’s area can result in language deficits. The types of deficits
are very different, however, depending on which area is affected.

The occipital lobe is located at the very back of the brain, and contains the primary visual cortex, which is

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responsible for interpreting incoming visual information. The occipital cortex is organized retinotopically,
which means there is a close relationship between the position of an object in a person’s visual field and
the position of that object’s representation on the cortex. You will learn much more about how visual
information is processed in the occipital lobe when you study sensation and perception.

Other Areas of the Forebrain

Other areas of the forebrain, located beneath the cerebral cortex, include the thalamus and the limbic
system. The thalamus is a sensory relay for the brain. All of our senses, with the exception of smell, are
routed through the thalamus before being directed to other areas of the brain for processing (Figure 3.22).

Figure 3.22 The thalamus serves as the relay center of the brain where most senses are routed for processing.

The limbic system is involved in processing both emotion and memory. Interestingly, the sense of smell
projects directly to the limbic system; therefore, not surprisingly, smell can evoke emotional responses
in ways that other sensory modalities cannot. The limbic system is made up of a number of different
structures, but three of the most important are the hippocampus, the amygdala, and the hypothalamus
(Figure 3.23). The hippocampus is an essential structure for learning and memory. The amygdala is
involved in our experience of emotion and in tying emotional meaning to our memories. The
hypothalamus regulates a number of homeostatic processes, including the regulation of body
temperature, appetite, and blood pressure. The hypothalamus also serves as an interface between the
nervous system and the endocrine system and in the regulation of sexual motivation and behavior.

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Figure 3.23 The limbic system is involved in mediating emotional response and memory.

The Case of Henry Molaison (H.M.)

In 1953, Henry Gustav Molaison (H. M.) was a 27-year-old man who experienced severe seizures. In
an attempt to control his seizures, H. M. underwent brain surgery to remove his hippocampus and
amygdala. Following the surgery, H.M’s seizures became much less severe, but he also suffered some
unexpected—and devastating—consequences of the surgery: he lost his ability to form many types of new
memories. For example, he was unable to learn new facts, such as who was president of the United States.
He was able to learn new skills, but afterward he had no recollection of learning them. For example, while
he might learn to use a computer, he would have no conscious memory of ever having used one. He could
not remember new faces, and he was unable to remember events, even immediately after they occurred.
Researchers were fascinated by his experience, and he is considered one of the most studied cases in
medical and psychological history (Hardt, Einarsson, & Nader, 2010; Squire, 2009). Indeed, his case has
provided tremendous insight into the role that the hippocampus plays in the consolidation of new learning
into explicit memory.

Clive Wearing, an accomplished musician, lost the ability to form new memories when his hippocampus
was damaged through illness. Check out the first few minutes of this documentary video about this
man and his condition (http://openstax.org/l/wearing) to learn more.

MIDBRAIN AND HINDBRAIN STRUCTURES

The midbrain is comprised of structures located deep within the brain, between the forebrain and the
hindbrain. The reticular formation is centered in the midbrain, but it actually extends up into the forebrain
and down into the hindbrain. The reticular formation is important in regulating the sleep/wake cycle,
arousal, alertness, and motor activity.

The substantia nigra (Latin for “black substance”) and the ventral tegmental area (VTA) are also located
in the midbrain (Figure 3.24). Both regions contain cell bodies that produce the neurotransmitter
dopamine, and both are critical for movement. Degeneration of the substantia nigra and VTA is involved
in Parkinson’s disease. In addition, these structures are involved in mood, reward, and addiction (Berridge

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& Robinson, 1998; Gardner, 2011; George, Le Moal, & Koob, 2012).

Figure 3.24 The substantia nigra and ventral tegmental area (VTA) are located in the midbrain.

The hindbrain is located at the back of the head and looks like an extension of the spinal cord. It contains
the medulla, pons, and cerebellum (Figure 3.25). The medulla controls the automatic processes of the
autonomic nervous system, such as breathing, blood pressure, and heart rate. The word pons literally
means “bridge,” and as the name suggests, the pons serves to connect the hindbrain to the rest of the brain.
It also is involved in regulating brain activity during sleep. The medulla, pons, and various structures are
known as the brainstem, and aspects of the brainstem span both the midbrain and the hindbrain.

Figure 3.25 The pons, medulla, and cerebellum make up the hindbrain.

The cerebellum (Latin for “little brain”) receives messages from muscles, tendons, joints, and structures
in our ear to control balance, coordination, movement, and motor skills. The cerebellum is also thought
to be an important area for processing some types of memories. In particular, procedural memory, or
memory involved in learning and remembering how to perform tasks, is thought to be associated with the
cerebellum. Recall that H. M. was unable to form new explicit memories, but he could learn new tasks.
This is likely due to the fact that H. M.’s cerebellum remained intact.

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Brain Dead and on Life Support

What would you do if your spouse or loved one was declared brain dead but his or her body was being kept
alive by medical equipment? Whose decision should it be to remove a feeding tube? Should medical care
costs be a factor?

On February 25, 1990, a Florida woman named Terri Schiavo went into cardiac arrest, apparently triggered by
a bulimic episode. She was eventually revived, but her brain had been deprived of oxygen for a long time. Brain
scans indicated that there was no activity in her cerebral cortex, and she suffered from severe and permanent
cerebral atrophy. Basically, Schiavo was in a vegetative state. Medical professionals determined that she would
never again be able to move, talk, or respond in any way. To remain alive, she required a feeding tube, and
there was no chance that her situation would ever improve.

On occasion, Schiavo’s eyes would move, and sometimes she would groan. Despite the doctors’ insistence to
the contrary, her parents believed that these were signs that she was trying to communicate with them.

After 12 years, Schiavo’s husband argued that his wife would not have wanted to be kept alive with no
feelings, sensations, or brain activity. Her parents, however, were very much against removing her feeding
tube. Eventually, the case made its way to the courts, both in the state of Florida and at the federal level. By
2005, the courts found in favor of Schiavo’s husband, and the feeding tube was removed on March 18, 2005.
Schiavo died 13 days later.

Why did Schiavo’s eyes sometimes move, and why did she groan? Although the parts of her brain that
control thought, voluntary movement, and feeling were completely damaged, her brainstem was still intact. Her
medulla and pons maintained her breathing and caused involuntary movements of her eyes and the occasional
groans. Over the 15-year period that she was on a feeding tube, Schiavo’s medical costs may have topped $7
million (Arnst, 2003).

These questions were brought to popular conscience decades ago in the case of Terri Schiavo, and they
have persisted. In 2013, a 13-year-old girl who suffered complications after tonsil surgery was declared brain
dead. There was a battle between her family, who wanted her to remain on life support, and the hospital’s
policies regarding persons declared brain dead. In another complicated 2013–14 case in Texas, a pregnant
EMT professional declared brain dead was kept alive for weeks, despite her spouse’s directives, which were
based on her wishes should this situation arise. In this case, state laws designed to protect an unborn fetus
came into consideration until doctors determined the fetus unviable.

Decisions surrounding the medical response to patients declared brain dead are complex. What do you think
about these issues?

BRAIN IMAGING

You have learned how brain injury can provide information about the functions of different parts of the
brain. Increasingly, however, we are able to obtain that information using brain imaging techniques on
individuals who have not suffered brain injury. In this section, we take a more in-depth look at some of the
techniques that are available for imaging the brain, including techniques that rely on radiation, magnetic
fields, or electrical activity within the brain.

Techniques Involving Radiation

A computerized tomography (CT) scan involves taking a number of x-rays of a particular section of a
person’s body or brain (Figure 3.26). The x-rays pass through tissues of different densities at different
rates, allowing a computer to construct an overall image of the area of the body being scanned. A CT scan
is often used to determine whether someone has a tumor or significant brain atrophy.

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Figure 3.26 A CT scan can be used to show brain tumors. (a) The image on the left shows a healthy brain, whereas
(b) the image on the right indicates a brain tumor in the left frontal lobe. (credit a: modification of work by
“Aceofhearts1968″/Wikimedia Commons; credit b: modification of work by Roland Schmitt et al)

Positron emission tomography (PET) scans create pictures of the living, active brain (Figure 3.27). An
individual receiving a PET scan drinks or is injected with a mildly radioactive substance, called a tracer.
Once in the bloodstream, the amount of tracer in any given region of the brain can be monitored. As
a brain area becomes more active, more blood flows to that area. A computer monitors the movement
of the tracer and creates a rough map of active and inactive areas of the brain during a given behavior.
PET scans show little detail, are unable to pinpoint events precisely in time, and require that the brain be
exposed to radiation; therefore, this technique has been replaced by the fMRI as an alternative diagnostic
tool. However, combined with CT, PET technology is still being used in certain contexts. For example,
CT/PET scans allow better imaging of the activity of neurotransmitter receptors and open new avenues in
schizophrenia research. In this hybrid CT/PET technology, CT contributes clear images of brain structures,
while PET shows the brain’s activity.

Figure 3.27 A PET scan is helpful for showing activity in different parts of the brain. (credit: Health and Human
Services Department, National Institutes of Health)

Techniques Involving Magnetic Fields

In magnetic resonance imaging (MRI), a person is placed inside a machine that generates a strong
magnetic field. The magnetic field causes the hydrogen atoms in the body’s cells to move. When the
magnetic field is turned off, the hydrogen atoms emit electromagnetic signals as they return to their
original positions. Tissues of different densities give off different signals, which a computer interprets and
displays on a monitor. Functional magnetic resonance imaging (fMRI) operates on the same principles,
but it shows changes in brain activity over time by tracking blood flow and oxygen levels. The fMRI
provides more detailed images of the brain’s structure, as well as better accuracy in time, than is possible
in PET scans (Figure 3.28). With their high level of detail, MRI and fMRI are often used to compare the

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brains of healthy individuals to the brains of individuals diagnosed with psychological disorders. This
comparison helps determine what structural and functional differences exist between these populations.

Figure 3.28 An fMRI shows activity in the brain over time. This image represents a single frame from an fMRI.
(credit: modification of work by Kim J, Matthews NL, Park S.)

Visit this virtual lab about MRI and fMRI (http://openstax.org/l/mri) to learn more.

Techniques Involving Electrical Activity

In some situations, it is helpful to gain an understanding of the overall activity of a person’s brain, without
needing information on the actual location of the activity. Electroencephalography (EEG) serves this
purpose by providing a measure of a brain’s electrical activity. An array of electrodes is placed around
a person’s head (Figure 3.29). The signals received by the electrodes result in a printout of the electrical
activity of his or her brain, or brainwaves, showing both the frequency (number of waves per second) and
amplitude (height) of the recorded brainwaves, with an accuracy within milliseconds. Such information is
especially helpful to researchers studying sleep patterns among individuals with sleep disorders.

Figure 3.29 Using caps with electrodes, modern EEG research can study the precise timing of overall brain
activities. (credit: SMI Eye Tracking)

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3.5 The Endocrine System

Learning Objectives

By the end of this section, you will be able to:
• Identify the major glands of the endocrine system
• Identify the hormones secreted by each gland
• Describe each hormone’s role in regulating bodily functions

The endocrine system consists of a series of glands that produce chemical substances known as hormones
(Figure 3.30). Like neurotransmitters, hormones are chemical messengers that must bind to a receptor in
order to send their signal. However, unlike neurotransmitters, which are released in close proximity to
cells with their receptors, hormones are secreted into the bloodstream and travel throughout the body,
affecting any cells that contain receptors for them. Thus, whereas neurotransmitters’ effects are localized,
the effects of hormones are widespread. Also, hormones are slower to take effect, and tend to be longer
lasting.

Figure 3.30 The major glands of the endocrine system are shown.

Hormones are involved in regulating all sorts of bodily functions, and they are ultimately controlled
through interactions between the hypothalamus (in the central nervous system) and the pituitary gland (in
the endocrine system). Imbalances in hormones are related to a number of disorders. This section explores
some of the major glands that make up the endocrine system and the hormones secreted by these glands
(Table 3.2).

MAJOR GLANDS

The pituitary gland descends from the hypothalamus at the base of the brain, and acts in close association
with it. The pituitary is often referred to as the “master gland” because its messenger hormones control

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all the other glands in the endocrine system, although it mostly carries out instructions from the
hypothalamus. In addition to messenger hormones, the pituitary also secretes growth hormone,
endorphins for pain relief, and a number of key hormones that regulate fluid levels in the body.

Located in the neck, the thyroid gland releases hormones that regulate growth, metabolism, and appetite.
In hyperthyroidism, or Grave’s disease, the thyroid secretes too much of the hormone thyroxine, causing
agitation, bulging eyes, and weight loss. In hypothyroidism, reduced hormone levels cause sufferers to
experience tiredness, and they often complain of feeling cold. Fortunately, thyroid disorders are often
treatable with medications that help reestablish a balance in the hormones secreted by the thyroid.

The adrenal glands sit atop our kidneys and secrete hormones involved in the stress response, such
as epinephrine (adrenaline) and norepinephrine (noradrenaline). The pancreas is an internal organ that
secretes hormones that regulate blood sugar levels: insulin and glucagon. These pancreatic hormones are
essential for maintaining stable levels of blood sugar throughout the day by lowering blood glucose levels
(insulin) or raising them (glucagon). People who suffer from diabetes do not produce enough insulin;
therefore, they must take medications that stimulate or replace insulin production, and they must closely
control the amount of sugars and carbohydrates they consume.

The gonads secrete sexual hormones, which are important in reproduction, and mediate both sexual
motivation and behavior. The female gonads are the ovaries; the male gonads are the testes. Ovaries
secrete estrogens and progesterone, and the testes secrete androgens, such as testosterone.

Major Endocrine Glands and Associated Hormone Functions

Endocrine
Gland

Associated Hormones Function

Hypothalamus Releasing and inhibiting hormones, such as
oxytocin

Regulate hormone release
from pituitary gland

Pituitary Growth hormone, releasing and inhibiting
hormones (such as thyroid stimulating hormone)

Regulate growth, regulate
hormone release

Thyroid Thyroxine, triiodothyronine Regulate metabolism and
appetite

Pineal Melatonin Regulate some biological
rhythms such as sleep cycles

Adrenal Epinephrine, norepinephrine Stress response, increase
metabolic activities

Pancreas Insulin, glucagon Regulate blood sugar levels

Ovaries Estrogen, progesterone Mediate sexual motivation
and behavior, reproduction

Testes Androgens, such as testosterone Mediate sexual motivation
and behavior, reproduction

Table 3.2

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Athletes and Anabolic Steroids

Although it is against Federal laws and many professional athletic associations (The National Football League,
for example) have banned their use, anabolic steroid drugs continue to be used by amateur and professional
athletes. The drugs are believed to enhance athletic performance. Anabolic steroid drugs mimic the effects
of the body’s own steroid hormones, like testosterone and its derivatives. These drugs have the potential to
provide a competitive edge by increasing muscle mass, strength, and endurance, although not all users may
experience these results. Moreover, use of performance-enhancing drugs (PEDs) does not come without risks.
Anabolic steroid use has been linked with a wide variety of potentially negative outcomes, ranging in severity
from largely cosmetic (acne) to life threatening (heart attack). Furthermore, use of these substances can result
in profound changes in mood and can increase aggressive behavior (National Institute on Drug Abuse, 2001).

Baseball player Alex Rodriguez (A-Rod) has been at the center of a media storm regarding his use of illegal
PEDs. Rodriguez’s performance on the field was unparalleled while using the drugs; his success played a
large role in negotiating a contract that made him the highest paid player in professional baseball. Although
Rodriguez maintains that he has not used PEDs for the several years, he received a substantial suspension
in 2013 that, if upheld, will cost him more than 20 million dollars in earnings (Gaines, 2013). What are your
thoughts on athletes and doping? Why or why not should the use of PEDs be banned? What advice would you
give an athlete who was considering using PEDs?

DIG DEEPER

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action potential

adrenal gland

agonist

all-or-none

allele

amygdala

antagonist

auditory cortex

autonomic nervous system

axon

biological perspective

Broca’s area

central nervous system (CNS)

cerebellum

cerebral cortex

chromosome

computerized tomography (CT) scan

corpus callosum

dendrite

deoxyribonucleic acid (DNA)

diabetes

dominant allele

electroencephalography (EEG)

endocrine system

epigenetics

Key Terms

electrical signal that moves down the neuron’s axon

sits atop our kidneys and secretes hormones involved in the stress response

drug that mimics or strengthens the effects of a neurotransmitter

phenomenon that incoming signal from another neuron is either sufficient or insufficient to
reach the threshold of excitation

specific version of a gene

structure in the limbic system involved in our experience of emotion and tying emotional
meaning to our memories

drug that blocks or impedes the normal activity of a given neurotransmitter

strip of cortex in the temporal lobe that is responsible for processing auditory
information

controls our internal organs and glands

major extension of the soma

view that psychological disorders like depression and schizophrenia are
associated with imbalances in one or more neurotransmitter systems

region in the left hemisphere that is essential for language production

brain and spinal cord

hindbrain structure that controls our balance, coordination, movement, and motor skills, and
it is thought to be important in processing some types of memory

surface of the brain that is associated with our highest mental capabilities

long strand of genetic information

imaging technique in which a computer coordinates and integrates
multiple x-rays of a given area

thick band of neural fibers connecting the brain’s two hemispheres

branch-like extension of the soma that receives incoming signals from other neurons

helix-shaped molecule made of nucleotide base pairs

disease related to insufficient insulin production

allele whose phenotype will be expressed in an individual that possesses that allele

recording the electrical activity of the brain via electrodes on the scalp

series of glands that produce chemical substances known as hormones

study of gene-environment interactions, such as how the same genotype leads to different
phenotypes

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fight or flight response

forebrain

fraternal twins

frontal lobe

functional magnetic resonance imaging (fMRI)

gene

genetic environmental correlation

genotype

glial cell

gonad

gyrus

hemisphere

heterozygous

hindbrain

hippocampus

homeostasis

homozygous

hormone

hypothalamus

identical twins

lateralization

limbic system

longitudinal fissure

magnetic resonance imaging (MRI)

activation of the sympathetic division of the autonomic nervous system,
allowing access to energy reserves and heightened sensory capacity so that we might fight off a given
threat or run away to safety

largest part of the brain, containing the cerebral cortex, the thalamus, and the limbic system,
among other structures

twins who develop from two different eggs fertilized by different sperm, so their genetic
material varies the same as in non-twin siblings

part of the cerebral cortex involved in reasoning, motor control, emotion, and language;
contains motor cortex

MRI that shows changes in metabolic activity over time

sequence of DNA that controls or partially controls physical characteristics

view of gene-environment interaction that asserts our genes affect
our environment, and our environment influences the expression of our genes

genetic makeup of an individual

nervous system cell that provides physical and metabolic support to neurons, including
neuronal insulation and communication, and nutrient and waste transport

secretes sexual hormones, which are important for successful reproduction, and mediate both
sexual motivation and behavior

(plural: gyri) bump or ridge on the cerebral cortex

left or right half of the brain

consisting of two different alleles

division of the brain containing the medulla, pons, and cerebellum

structure in the temporal lobe associated with learning and memory

state of equilibrium—biological conditions, such as body temperature, are maintained at
optimal levels

consisting of two identical alleles

chemical messenger released by endocrine glands

forebrain structure that regulates sexual motivation and behavior and a number of
homeostatic processes; serves as an interface between the nervous system and the endocrine system

twins that develop from the same sperm and egg

concept that each hemisphere of the brain is associated with specialized functions

collection of structures involved in processing emotion and memory

deep groove in the brain’s cortex

magnetic fields used to produce a picture of the tissue being imaged

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medulla

membrane potential

midbrain

motor cortex

mutation

myelin sheath

neuron

neuroplasticity

neurotransmitter

Nodes of Ranvier

occipital lobe

pancreas

parasympathetic nervous system

parietal lobe

peripheral nervous system (PNS)

phenotype

pituitary gland

polygenic

pons

positron emission tomography (PET) scan

prefrontal cortex

psychotropic medication

range of reaction

receptor

hindbrain structure that controls automated processes like breathing, blood pressure, and heart
rate

difference in charge across the neuronal membrane

division of the brain located between the forebrain and the hindbrain; contains the reticular
formation

strip of cortex involved in planning and coordinating movement

sudden, permanent change in a gene

fatty substance that insulates axons

cells in the nervous system that act as interconnected information processors, which are essential
for all of the tasks of the nervous system

nervous system’s ability to change

chemical messenger of the nervous system

open spaces that are found in the myelin sheath that encases the axon

part of the cerebral cortex associated with visual processing; contains the primary visual
cortex

secretes hormones that regulate blood sugar

associated with routine, day-to-day operations of the body

part of the cerebral cortex involved in processing various sensory and perceptual
information; contains the primary somatosensory cortex

connects the brain and spinal cord to the muscles, organs and senses
in the periphery of the body

individual’s inheritable physical characteristics

secretes a number of key hormones, which regulate fluid levels in the body, and a
number of messenger hormones, which direct the activity of other glands in the endocrine system

multiple genes affecting a given trait

hindbrain structure that connects the brain and spinal cord; involved in regulating brain activity
during sleep

involves injecting individuals with a mildly radioactive
substance and monitoring changes in blood flow to different regions of the brain

area in the frontal lobe responsible for higher-level cognitive functioning

drugs that treat psychiatric symptoms by restoring neurotransmitter balance

asserts our genes set the boundaries within which we can operate, and our
environment interacts with the genes to determine where in that range we will fall

protein on the cell surface where neurotransmitters attach

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recessive allele

resting potential

reticular formation

reuptake

semipermeable membrane

soma

somatic nervous system

somatosensory cortex

substantia nigra

sulcus

sympathetic nervous system

synaptic cleft

synaptic vesicle

temporal lobe

terminal button

thalamus

theory of evolution by natural selection

threshold of excitation

thyroid

ventral tegmental area (VTA)

Wernicke’s area

allele whose phenotype will be expressed only if an individual is homozygous for that
allele

the state of readiness of a neuron membrane’s potential between signals

midbrain structure important in regulating the sleep/wake cycle, arousal, alertness,
and motor activity

neurotransmitter is pumped back into the neuron that released it

cell membrane that allows smaller molecules or molecules without an
electrical charge to pass through it, while stopping larger or highly charged molecules

cell body

relays sensory and motor information to and from the CNS

essential for processing sensory information from across the body, such as touch,
temperature, and pain

midbrain structure where dopamine is produced; involved in control of movement

(plural: sulci) depressions or grooves in the cerebral cortex

involved in stress-related activities and functions

small gap between two neurons where communication occurs

storage site for neurotransmitters

part of cerebral cortex associated with hearing, memory, emotion, and some aspects of
language; contains primary auditory cortex

axon terminal containing synaptic vesicles

sensory relay for the brain

states that organisms that are better suited for their
environments will survive and reproduce compared to those that are poorly suited for their
environments

level of charge in the membrane that causes the neuron to become active

secretes hormones that regulate growth, metabolism, and appetite

midbrain structure where dopamine is produced: associated with mood,
reward, and addiction

important for speech comprehension

Summary

3.1 Human Genetics
Genes are sequences of DNA that code for a particular trait. Different versions of a gene are called
alleles—sometimes alleles can be classified as dominant or recessive. A dominant allele always results in
the dominant phenotype. In order to exhibit a recessive phenotype, an individual must be homozygous

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for the recessive allele. Genes affect both physical and psychological characteristics. Ultimately, how and
when a gene is expressed, and what the outcome will be—in terms of both physical and psychological
characteristics—is a function of the interaction between our genes and our environments.

3.2 Cells of the Nervous System
Glia and neurons are the two cell types that make up the nervous system. While glia generally play
supporting roles, the communication between neurons is fundamental to all of the functions associated
with the nervous system. Neuronal communication is made possible by the neuron’s specialized
structures. The soma contains the cell nucleus, and the dendrites extend from the soma in tree-like
branches. The axon is another major extension of the cell body; axons are often covered by a myelin sheath,
which increases the speed of transmission of neural impulses. At the end of the axon are terminal buttons
that contain synaptic vesicles filled with neurotransmitters.

Neuronal communication is an electrochemical event. The dendrites contain receptors for
neurotransmitters released by nearby neurons. If the signals received from other neurons are sufficiently
strong, an action potential will travel down the length of the axon to the terminal buttons, resulting in the
release of neurotransmitters into the synaptic cleft. Action potentials operate on the all-or-none principle
and involve the movement of Na+ and K+ across the neuronal membrane.

Different neurotransmitters are associated with different functions. Often, psychological disorders involve
imbalances in a given neurotransmitter system. Therefore, psychotropic drugs are prescribed in an attempt
to bring the neurotransmitters back into balance. Drugs can act either as agonists or as antagonists for a
given neurotransmitter system.

3.3 Parts of the Nervous System
The brain and spinal cord make up the central nervous system. The peripheral nervous system is
comprised of the somatic and autonomic nervous systems. The somatic nervous system transmits sensory
and motor signals to and from the central nervous system. The autonomic nervous system controls the
function of our organs and glands, and can be divided into the sympathetic and parasympathetic divisions.
Sympathetic activation prepares us for fight or flight, while parasympathetic activation is associated with
normal functioning under relaxed conditions.

3.4 The Brain and Spinal Cord
The brain consists of two hemispheres, each controlling the opposite side of the body. Each hemisphere
can be subdivided into different lobes: frontal, parietal, temporal, and occipital. In addition to the lobes
of the cerebral cortex, the forebrain includes the thalamus (sensory relay) and limbic system (emotion and
memory circuit). The midbrain contains the reticular formation, which is important for sleep and arousal,
as well as the substantia nigra and ventral tegmental area. These structures are important for movement,
reward, and addictive processes. The hindbrain contains the structures of the brainstem (medulla, pons,
and midbrain), which control automatic functions like breathing and blood pressure. The hindbrain also
contains the cerebellum, which helps coordinate movement and certain types of memories.

Individuals with brain damage have been studied extensively to provide information about the role of
different areas of the brain, and recent advances in technology allow us to glean similar information by
imaging brain structure and function. These techniques include CT, PET, MRI, fMRI, and EEG.

3.5 The Endocrine System
The glands of the endocrine system secrete hormones to regulate normal body functions. The
hypothalamus serves as the interface between the nervous system and the endocrine system, and it
controls the secretions of the pituitary. The pituitary serves as the master gland, controlling the secretions
of all other glands. The thyroid secretes thyroxine, which is important for basic metabolic processes
and growth; the adrenal glands secrete hormones involved in the stress response; the pancreas secretes
hormones that regulate blood sugar levels; and the ovaries and testes produce sex hormones that regulate
sexual motivation and behavior.

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Review Questions

1. A(n) ________ is a sudden, permanent change
in a sequence of DNA.

a. allele
b. chromosome
c. epigenetic
d. mutation

2. ________ refers to a person’s genetic makeup,
while ________ refers to a person’s physical
characteristics.

a. Phenotype; genotype
b. Genotype; phenotype
c. DNA; gene
d. Gene; DNA

3. ________ is the field of study that focuses on
genes and their expression.

a. Social psychology
b. Evolutionary psychology
c. Epigenetics
d. Behavioral neuroscience

4. Humans have ________ pairs of chromosomes.
a. 15
b. 23
c. 46
d. 78

5. The ________ receive(s) incoming signals from
other neurons.

a. soma
b. terminal buttons
c. myelin sheath
d. dendrites

6. A(n) ________ facilitates or mimics the activity
of a given neurotransmitter system.

a. axon
b. SSRI
c. agonist
d. antagonist

7. Multiple sclerosis involves a breakdown of the
________.

a. soma
b. myelin sheath
c. synaptic vesicles
d. dendrites

8. An action potential involves Na+ moving
________ the cell and K+ moving ________ the cell.

a. inside; outside
b. outside; inside
c. inside; inside
d. outside; outside

9. Our ability to make our legs move as we walk
across the room is controlled by the ________
nervous system.

a. autonomic
b. somatic
c. sympathetic
d. parasympathetic

10. If your ________ is activated, you will feel
relatively at ease.

a. somatic nervous system
b. sympathetic nervous system
c. parasympathetic nervous system
d. spinal cord

11. The central nervous system is comprised of
________.

a. sympathetic and parasympathetic nervous
systems

b. organs and glands
c. somatic and autonomic nervous systems
d. brain and spinal cord

12. Sympathetic activation is associated with
________.

a. pupil dilation
b. storage of glucose in the liver
c. increased heart rate
d. both A and C

13. The ________ is a sensory relay station where
all sensory information, except for smell, goes
before being sent to other areas of the brain for
further processing.

a. amygdala
b. hippocampus
c. hypothalamus
d. thalamus

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14. Damage to the ________ disrupts one’s ability
to comprehend language, but it leaves one’s ability
to produce words intact.

a. amygdala
b. Broca’s Area
c. Wernicke’s Area
d. occipital lobe

15. A(n) ________ uses magnetic fields to create
pictures of a given tissue.

a. EEG
b. MRI
c. PET scan
d. CT scan

16. Which of the following is not a structure of
the forebrain?

a. thalamus
b. hippocampus
c. amygdala
d. substantia nigra

17. The two major hormones secreted from the
pancreas are:

a. estrogen and progesterone
b. norepinephrine and epinephrine
c. thyroxine and oxytocin
d. glucagon and insulin

18. The ________ secretes messenger hormones
that direct the function of the rest of the endocrine
glands.

a. ovary
b. thyroid
c. pituitary
d. pancreas

19. The ________ gland secretes epinephrine.
a. adrenal
b. thyroid
c. pituitary
d. master

20. The ________ secretes hormones that regulate
the body’s fluid levels.

a. adrenal
b. pituitary
c. testes
d. thyroid

Critical Thinking Questions

21. The theory of evolution by natural selection requires variability of a given trait. Why is variability
necessary and where does it come from?

22. Cocaine has two effects on synaptic transmission: it impairs reuptake of dopamine and it causes more
dopamine to be released into the synaptic cleft. Would cocaine be classified as an agonist or antagonist?
Why?

23. Drugs such as lidocaine and novocaine act as Na+ channel blockers. In other words, they prevent
sodium from moving across the neuronal membrane. Why would this particular effect make these drugs
such effective local anesthetics?

24. What are the implications of compromised immune function as a result of exposure to chronic stress?

25. Examine Figure 3.14, illustrating the effects of sympathetic nervous system activation. How would
all of these things play into the fight or flight response?

26. Before the advent of modern imaging techniques, scientists and clinicians relied on autopsies of
people who suffered brain injury with resultant change in behavior to determine how different areas of
the brain were affected. What are some of the limitations associated with this kind of approach?

Chapter 3 | Biopsychology 113

27. Which of the techniques discussed would be viable options for you to determine how activity in the
reticular formation is related to sleep and wakefulness? Why?

28. Hormone secretion is often regulated through a negative feedback mechanism, which means that once
a hormone is secreted it will cause the hypothalamus and pituitary to shut down the production of signals
necessary to secrete the hormone in the first place. Most oral contraceptives are made of small doses of
estrogen and/or progesterone. Why would this be an effective means of contraception?

29. Chemical messengers are used in both the nervous system and the endocrine system. What properties
do these two systems share? What properties are different? Which one would be faster? Which one would
result in long-lasting changes?

Personal Application Questions

30. You share half of your genetic makeup with each of your parents, but you are no doubt very different
from both of them. Spend a few minutes jotting down the similarities and differences between you and
your parents. How do you think your unique environment and experiences have contributed to some of
the differences you see?

31. Have you or someone you know ever been prescribed a psychotropic medication? If so, what side
effects were associated with the treatment?

32. Hopefully, you do not face real physical threats from potential predators on a daily basis. However,
you probably have your fair share of stress. What situations are your most common sources of stress? What
can you do to try to minimize the negative consequences of these particular stressors in your life?

33. You read about H. M.’s memory deficits following the bilateral removal of his hippocampus and
amygdala. Have you encountered a character in a book, television program, or movie that suffered
memory deficits? How was that character similar to and different from H. M.?

34. Given the negative health consequences associated with the use of anabolic steroids, what kinds of
considerations might be involved in a person’s decision to use them?

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Chapter 4

States of Consciousness

Figure 4.1 Sleep, which we all experience, is a quiet and mysterious pause in our daily lives. Two sleeping children
are depicted in this 1895 oil painting titled Zwei schlafende Mädchen auf der Ofenbank, which translates as “two
sleeping girls on the stove,” by Swiss painter Albert Anker.

Chapter Outline

4.1 What Is Consciousness?

4.2 Sleep and Why We Sleep

4.3 Stages of Sleep

4.4 Sleep Problems and Disorders

4.5 Substance Use and Abuse

4.6 Other States of Consciousness

Introduction

Our lives involve regular, dramatic changes in the degree to which we are aware of our surroundings and
our internal states. While awake, we feel alert and aware of the many important things going on around us.
Our experiences change dramatically while we are in deep sleep and once again when we are dreaming.
Some people also experience altered states of consciousness through meditation, hypnosis, or alcohol and
other drugs.

This chapter will discuss states of consciousness with a particular emphasis on sleep. The different stages
of sleep will be identified, and sleep disorders will be described. The chapter will close with discussions of
altered states of consciousness produced by psychoactive drugs, hypnosis, and meditation.

Chapter 4 | States of Consciousness 115

4.1 What Is Consciousness?

Learning Objectives

By the end of this section, you will be able to:
• Understand what is meant by consciousness
• Explain how circadian rhythms are involved in regulating the sleep-wake cycle, and how

circadian cycles can be disrupted
• Discuss the concept of sleep debt

Consciousness describes our awareness of internal and external stimuli. Awareness of internal stimuli
includes feeling pain, hunger, thirst, sleepiness, and being aware of our thoughts and emotions. Awareness
of external stimuli includes experiences such as seeing the light from the sun, feeling the warmth of a room,
and hearing the voice of a friend.

We experience different states of consciousness and different levels of awareness on a regular basis. We
might even describe consciousness as a continuum that ranges from full awareness to a deep sleep. Sleep
is a state marked by relatively low levels of physical activity and reduced sensory awareness that is
distinct from periods of rest that occur during wakefulness. Wakefulness is characterized by high levels
of sensory awareness, thought, and behavior. Beyond being awake or asleep, there are many other states
of consciousness people experience. These include daydreaming, intoxication, and unconsciousness due to
anesthesia. We might also experience unconscious states of being via drug-induced anesthesia for medical
purposes. Often, we are not completely aware of our surroundings, even when we are fully awake. For
instance, have you ever daydreamed while driving home from work or school without really thinking
about the drive itself? You were capable of engaging in the all of the complex tasks involved with operating
a motor vehicle even though you were not aware of doing so. Many of these processes, like much of
psychological behavior, are rooted in our biology.

BIOLOGICAL RHYTHMS

Biological rhythms are internal rhythms of biological activity. A woman’s menstrual cycle is an example
of a biological rhythm—a recurring, cyclical pattern of bodily changes. One complete menstrual cycle
takes about 28 days—a lunar month—but many biological cycles are much shorter. For example, body
temperature fluctuates cyclically over a 24-hour period (Figure 4.2). Alertness is associated with higher
body temperatures, and sleepiness with lower body temperatures.

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Figure 4.2 This chart illustrates the circadian change in body temperature over 28 hours in a group of eight young
men. Body temperature rises throughout the waking day, peaking in the afternoon, and falls during sleep with the
lowest point occurring during the very early morning hours.

This pattern of temperature fluctuation, which repeats every day, is one example of a circadian rhythm. A
circadian rhythm is a biological rhythm that takes place over a period of about 24 hours. Our sleep-wake
cycle, which is linked to our environment’s natural light-dark cycle, is perhaps the most obvious example
of a circadian rhythm, but we also have daily fluctuations in heart rate, blood pressure, blood sugar, and
body temperature. Some circadian rhythms play a role in changes in our state of consciousness.

If we have biological rhythms, then is there some sort of biological clock? In the brain, the hypothalamus,
which lies above the pituitary gland, is a main center of homeostasis. Homeostasis is the tendency to
maintain a balance, or optimal level, within a biological system.

The brain’s clock mechanism is located in an area of the hypothalamus known as the suprachiasmatic
nucleus (SCN). The axons of light-sensitive neurons in the retina provide information to the SCN based on
the amount of light present, allowing this internal clock to be synchronized with the outside world (Klein,
Moore, & Reppert, 1991; Welsh, Takahashi, & Kay, 2010) (Figure 4.3).

Chapter 4 | States of Consciousness 117

Figure 4.3 The suprachiasmatic nucleus (SCN) serves as the brain’s clock mechanism. The clock sets itself with
light information received through projections from the retina.

PROBLEMS WITH CIRCADIAN RHYTHMS

Generally, and for most people, our circadian cycles are aligned with the outside world. For example, most
people sleep during the night and are awake during the day. One important regulator of sleep-wake cycles
is the hormone melatonin. The pineal gland, an endocrine structure located inside the brain that releases
melatonin, is thought to be involved in the regulation of various biological rhythms and of the immune
system during sleep (Hardeland, Pandi-Perumal, & Cardinali, 2006). Melatonin release is stimulated by
darkness and inhibited by light.

There are individual differences in regard to our sleep-wake cycle. For instance, some people would say
they are morning people, while others would consider themselves to be night owls. These individual
differences in circadian patterns of activity are known as a person’s chronotype, and research
demonstrates that morning larks and night owls differ with regard to sleep regulation (Taillard, Philip,
Coste, Sagaspe, & Bioulac, 2003). Sleep regulation refers to the brain’s control of switching between sleep
and wakefulness as well as coordinating this cycle with the outside world.

Watch this brief video about circadian rhythms and how they affect sleep (http://openstax.org/l/
circadian) to learn more.

Disruptions of Normal Sleep

Whether lark, owl, or somewhere in between, there are situations in which a person’s circadian clock gets
out of synchrony with the external environment. One way that this happens involves traveling across
multiple time zones. When we do this, we often experience jet lag. Jet lag is a collection of symptoms that
results from the mismatch between our internal circadian cycles and our environment. These symptoms
include fatigue, sluggishness, irritability, and insomnia (i.e., a consistent difficulty in falling or staying
asleep for at least three nights a week over a month’s time) (Roth, 2007).

Individuals who do rotating shift work are also likely to experience disruptions in circadian cycles.

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Rotating shift work refers to a work schedule that changes from early to late on a daily or weekly
basis. For example, a person may work from 7:00 a.m. to 3:00 p.m. on Monday, 3:00 a.m. to 11:00 a.m.
on Tuesday, and 11:00 a.m. to 7:00 p.m. on Wednesday. In such instances, the individual’s schedule
changes so frequently that it becomes difficult for a normal circadian rhythm to be maintained. This
often results in sleeping problems, and it can lead to signs of depression and anxiety. These kinds of
schedules are common for individuals working in health care professions and service industries, and they
are associated with persistent feelings of exhaustion and agitation that can make someone more prone to
making mistakes on the job (Gold et al., 1992; Presser, 1995).

Rotating shift work has pervasive effects on the lives and experiences of individuals engaged in that
kind of work, which is clearly illustrated in stories reported in a qualitative study that researched the
experiences of middle-aged nurses who worked rotating shifts (West, Boughton & Byrnes, 2009). Several of
the nurses interviewed commented that their work schedules affected their relationships with their family.
One of the nurses said,

If you’ve had a partner who does work regular job 9 to 5 office hours . . . the ability to spend
time, good time with them when you’re not feeling absolutely exhausted . . . that would be one
of the problems that I’ve encountered. (West et al., 2009, p. 114)

While disruptions in circadian rhythms can have negative consequences, there are things we can do to help
us realign our biological clocks with the external environment. Some of these approaches, such as using
a bright light as shown in Figure 4.4, have been shown to alleviate some of the problems experienced by
individuals suffering from jet lag or from the consequences of rotating shift work. Because the biological
clock is driven by light, exposure to bright light during working shifts and dark exposure when not
working can help combat insomnia and symptoms of anxiety and depression (Huang, Tsai, Chen, & Hsu,
2013).

Figure 4.4 Devices like this are designed to provide exposure to bright light to help people maintain a regular
circadian cycle. They can be helpful for people working night shifts or for people affected by seasonal variations in
light.

Watch this video about overcoming jet lag (http://openstax.org/l/jetlag) to learn some tips.

Insufficient Sleep

When people have difficulty getting sleep due to their work or the demands of day-to-day life, they
accumulate a sleep debt. A person with a sleep debt does not get sufficient sleep on a chronic basis. The
consequences of sleep debt include decreased levels of alertness and mental efficiency. Interestingly, since
the advent of electric light, the amount of sleep that people get has declined. While we certainly welcome

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the convenience of having the darkness lit up, we also suffer the consequences of reduced amounts of sleep
because we are more active during the nighttime hours than our ancestors were. As a result, many of us
sleep less than 7–8 hours a night and accrue a sleep debt. While there is tremendous variation in any given
individual’s sleep needs, the National Sleep Foundation (n.d.) cites research to estimate that newborns
require the most sleep (between 12 and 18 hours a night) and that this amount declines to just 7–9 hours
by the time we are adults.

If you lie down to take a nap and fall asleep very easily, chances are you may have sleep debt. Given that
college students are notorious for suffering from significant sleep debt (Hicks, Fernandez, & Pelligrini,
2001; Hicks, Johnson, & Pelligrini, 1992; Miller, Shattuck, & Matsangas, 2010), chances are you and your
classmates deal with sleep debt-related issues on a regular basis. In 2015, the National Sleep Foundation
updated their sleep duration hours, to better accommodate individual differences. Table 4.1 shows the
new recommendations, which describe sleep durations that are “recommended”, “may be appropriate”,
and “not recommended”.

Sleep Needs at Different Ages

Age Recommended May be appropriate Not recommended

0–3 months 14–17 hours 11–13 hours
18–19 hours

Fewer than 11 hours
More than 19 hours

4–11 months 12–15 hours 10–11 hours
16–18 hours

Fewer than 10 hours
More than 18 hours

1–2 years 11–14 hours 9–10 hours
15–16 hours

Fewer than 9 hours
More than 16 hours

3–5 years 10–13 hours 8–9 hours
14 hours

Fewer than 8 hours
More than 14 hours

6–13 years 9–11 hours 7–8 hours
12 hours

Fewer than 7 hours
More than 12 hours

14–17 years 8–10 hours 7 hours
11 hours

Fewer than 7 hours
More than 11 hours

18–25 years 7–9 hours 6 hours
10–11 hours

Fewer than 6 hours
More than 11 hours

26–64 years 7–9 hours 6 hours
10 hours

Fewer than 6 hours
More than 10 hours

≥65 years 7–8 hours 5–6 hours
9 hours

Fewer than 5 hours
More than 9 hours

Table 4.1

Sleep debt and sleep deprivation have significant negative psychological and physiological consequences
Figure 4.5. As mentioned earlier, lack of sleep can result in decreased mental alertness and cognitive
function. In addition, sleep deprivation often results in depression-like symptoms. These effects can occur
as a function of accumulated sleep debt or in response to more acute periods of sleep deprivation. It may
surprise you to know that sleep deprivation is associated with obesity, increased blood pressure, increased
levels of stress hormones, and reduced immune functioning (Banks & Dinges, 2007). A sleep deprived

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individual generally will fall asleep more quickly than if she were not sleep deprived. Some sleep-deprived
individuals have difficulty staying awake when they stop moving (example sitting and watching television
or driving a car). That is why individuals suffering from sleep deprivation can also put themselves and
others at risk when they put themselves behind the wheel of a car or work with dangerous machinery.
Some research suggests that sleep deprivation affects cognitive and motor function as much as, if not more
than, alcohol intoxication (Williamson & Feyer, 2000). Research shows that the most severe effects of sleep
deprivation occur when a person stays awake for more than 24 hours (Killgore & Weber, 2014; Killgore
et al., 2007), or following repeated nights with fewer than four hours in bed (Wickens, Hutchins, Lauk,
Seebook, 2015). For example, irritability, distractibility, and impairments in cognitive and moral judgment
can occur with fewer than four hours of sleep. If someone stays awake for 48 consecutive hours, they could
start to hallucinate.

Figure 4.5 This figure illustrates some of the negative consequences of sleep deprivation. While cognitive deficits
may be the most obvious, many body systems are negatively impacted by lack of sleep. (credit: modification of work
by Mikael Häggström)

Read this article about sleep needs (http://openstax.org/l/sleephabits) to assess your own sleeping
habits.

The amount of sleep we get varies across the lifespan. When we are very young, we spend up to 16 hours
a day sleeping. As we grow older, we sleep less. In fact, a meta-analysis, which is a study that combines
the results of many related studies, conducted within the last decade indicates that by the time we are 65
years old, we average fewer than 7 hours of sleep per day (Ohayon, Carskadon, Guilleminault, & Vitiello,
2004).

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4.2 Sleep and Why We Sleep

Learning Objectives

By the end of this section, you will be able to:
• Describe areas of the brain involved in sleep
• Understand hormone secretions associated with sleep
• Describe several theories aimed at explaining the function of sleep

We spend approximately one-third of our lives sleeping. Given the average life expectancy for U.S. citizens
falls between 73 and 79 years old (Singh & Siahpush, 2006), we can expect to spend approximately 25 years
of our lives sleeping. Some animals never sleep (e.g., some fish and amphibian species); other animals sleep
very little without apparent negative consequences (e.g., giraffes); yet some animals (e.g., rats) die after
two weeks of sleep deprivation (Siegel, 2008). Why do we devote so much time to sleeping? Is it absolutely
essential that we sleep? This section will consider these questions and explore various explanations for
why we sleep.

WHAT IS SLEEP?

You have read that sleep is distinguished by low levels of physical activity and reduced sensory
awareness. As discussed by Siegel (2008), a definition of sleep must also include mention of the interplay
of the circadian and homeostatic mechanisms that regulate sleep. Homeostatic regulation of sleep is
evidenced by sleep rebound following sleep deprivation. Sleep rebound refers to the fact that a sleep-
deprived individual will fall asleep more quickly during subsequent opportunities for sleep. Sleep is
characterized by certain patterns of activity of the brain that can be visualized using
electroencephalography (EEG), and different phases of sleep can be differentiated using EEG as well.

Sleep-wake cycles seem to be controlled by multiple brain areas acting in conjunction with one another.
Some of these areas include the thalamus, the hypothalamus, and the pons. As already mentioned, the
hypothalamus contains the SCN—the biological clock of the body—in addition to other nuclei that, in
conjunction with the thalamus, regulate slow-wave sleep. The pons is important for regulating rapid eye
movement (REM) sleep (National Institutes of Health, n.d.).

Sleep is also associated with the secretion and regulation of a number of hormones from several endocrine
glands including: melatonin, follicle stimulating hormone (FSH), luteinizing hormone (LH), and growth
hormone (National Institutes of Health, n.d.). You have read that the pineal gland releases melatonin
during sleep (Figure 4.6). Melatonin is thought to be involved in the regulation of various biological
rhythms and the immune system (Hardeland et al., 2006). During sleep, the pituitary gland secretes both
FSH and LH which are important in regulating the reproductive system (Christensen et al., 2012; Sofikitis
et al., 2008). The pituitary gland also secretes growth hormone, during sleep, which plays a role in physical
growth and maturation as well as other metabolic processes (Bartke, Sun, & Longo, 2013).

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Figure 4.6 The pineal and pituitary glands secrete a number of hormones during sleep.

WHY DO WE SLEEP?

Given the central role that sleep plays in our lives and the number of adverse consequences that have been
associated with sleep deprivation, one would think that we would have a clear understanding of why it
is that we sleep. Unfortunately, this is not the case; however, several hypotheses have been proposed to
explain the function of sleep.

Adaptive Function of Sleep

One popular hypothesis of sleep incorporates the perspective of evolutionary psychology. Evolutionary
psychology is a discipline that studies how universal patterns of behavior and cognitive processes have
evolved over time as a result of natural selection. Variations and adaptations in cognition and behavior
make individuals more or less successful in reproducing and passing their genes to their offspring. One
hypothesis from this perspective might argue that sleep is essential to restore resources that are expended
during the day. Just as bears hibernate in the winter when resources are scarce, perhaps people sleep at
night to reduce their energy expenditures. While this is an intuitive explanation of sleep, there is little
research that supports this explanation. In fact, it has been suggested that there is no reason to think that
energetic demands could not be addressed with periods of rest and inactivity (Frank, 2006; Rial et al., 2007),
and some research has actually found a negative correlation between energetic demands and the amount
of time spent sleeping (Capellini, Barton, McNamara, Preston, & Nunn, 2008).

Another evolutionary hypothesis of sleep holds that our sleep patterns evolved as an adaptive response
to predatory risks, which increase in darkness. Thus we sleep in safe areas to reduce the chance of harm.
Again, this is an intuitive and appealing explanation for why we sleep. Perhaps our ancestors spent
extended periods of time asleep to reduce attention to themselves from potential predators. Comparative
research indicates, however, that the relationship that exists between predatory risk and sleep is very
complex and equivocal. Some research suggests that species that face higher predatory risks sleep fewer
hours than other species (Capellini et al., 2008), while other researchers suggest there is no relationship
between the amount of time a given species spends in deep sleep and its predation risk (Lesku, Roth,
Amlaner, & Lima, 2006).

It is quite possible that sleep serves no single universally adaptive function, and different species have
evolved different patterns of sleep in response to their unique evolutionary pressures. While we have
discussed the negative outcomes associated with sleep deprivation, it should be pointed out that there
are many benefits that are associated with adequate amounts of sleep. A few such benefits listed by the

Chapter 4 | States of Consciousness 123

National Sleep Foundation (n.d.) include maintaining healthy weight, lowering stress levels, improving
mood, and increasing motor coordination, as well as a number of benefits related to cognition and memory
formation.

Cognitive Function of Sleep

Another theory regarding why we sleep involves sleep’s importance for cognitive function and memory
formation (Rattenborg, Lesku, Martinez-Gonzalez, & Lima, 2007). Indeed, we know sleep deprivation
results in disruptions in cognition and memory deficits (Brown, 2012), leading to impairments in our
abilities to maintain attention, make decisions, and recall long-term memories. Moreover, these
impairments become more severe as the amount of sleep deprivation increases (Alhola & Polo-Kantola,
2007). Furthermore, slow-wave sleep after learning a new task can improve resultant performance on that
task (Huber, Ghilardi, Massimini, & Tononi, 2004) and seems essential for effective memory formation
(Stickgold, 2005). Understanding the impact of sleep on cognitive function should help you understand
that cramming all night for a test may be not effective and can even prove counterproductive.

Watch this brief video that gives sleep tips for college students (http://openstax.org/l/sleeptips) to
learn more.

Getting the optimal amount of sleep has also been associated with other cognitive benefits. Research
indicates that included among these possible benefits are increased capacities for creative thinking (Cai,
Mednick, Harrison, Kanady, & Mednick, 2009; Wagner, Gais, Haider, Verleger, & Born, 2004), language
learning (Fenn, Nusbaum, & Margoliash, 2003; Gómez, Bootzin, & Nadel, 2006), and inferential judgments
(Ellenbogen, Hu, Payne, Titone, & Walker, 2007). It is possible that even the processing of emotional
information is influenced by certain aspects of sleep (Walker, 2009).

Watch this brief video about the relationship between sleep and memory (http://openstax.org/l/
sleepmemory) to learn more.

4.3 Stages of Sleep

Learning Objectives

By the end of this section, you will be able to:
• Differentiate between REM and non-REM sleep
• Describe the differences between the three stages of non-REM sleep
• Understand the role that REM and non-REM sleep play in learning and memory

Sleep is not a uniform state of being. Instead, sleep is composed of several different stages that can
be differentiated from one another by the patterns of brain wave activity that occur during each stage.
These changes in brain wave activity can be visualized using EEG and are distinguished from one

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another by both the frequency and amplitude of brain waves (Figure 4.7). Sleep can be divided into
two different general phases: REM sleep and non-REM (NREM) sleep. Rapid eye movement (REM)
sleep is characterized by darting movements of the eyes under closed eyelids. Brain waves during REM
sleep appear very similar to brain waves during wakefulness. In contrast, non-REM (NREM) sleep is
subdivided into four stages distinguished from each other and from wakefulness by characteristic patterns
of brain waves. The first three stages of sleep are NREM sleep, while the fourth and final stage of sleep
is REM sleep. In this section, we will discuss each of these stages of sleep and their associated patterns of
brain wave activity.

Figure 4.7 Brainwave activity changes dramatically across the different stages of sleep. (credit “sleeping”:
modification of work by Ryan Vaarsi)

NREM STAGES OF SLEEP

The first stage of NREM sleep is known as stage 1 sleep. Stage 1 sleep is a transitional phase that occurs
between wakefulness and sleep, the period during which we drift off to sleep. During this time, there is
a slowdown in both the rates of respiration and heartbeat. In addition, stage 1 sleep involves a marked
decrease in both overall muscle tension and core body temperature.

In terms of brain wave activity, stage 1 sleep is associated with both alpha and theta waves. The early
portion of stage 1 sleep produces alpha waves, which are relatively low frequency (8–13Hz), high
amplitude patterns of electrical activity (waves) that become synchronized (Figure 4.8). This pattern of
brain wave activity resembles that of someone who is very relaxed, yet awake. As an individual continues
through stage 1 sleep, there is an increase in theta wave activity. Theta waves are even lower frequency
(4–7 Hz), higher amplitude brain waves than alpha waves. It is relatively easy to wake someone from stage
1 sleep; in fact, people often report that they have not been asleep if they are awoken during stage 1 sleep.

Chapter 4 | States of Consciousness 125

Figure 4.8 Brainwave activity changes dramatically across the different stages of sleep.

As we move into stage 2 sleep, the body goes into a state of deep relaxation. Theta waves still dominate
the activity of the brain, but they are interrupted by brief bursts of activity known as sleep spindles
(Figure 4.9). A sleep spindle is a rapid burst of higher frequency brain waves that may be important for
learning and memory (Fogel & Smith, 2011; Poe, Walsh, & Bjorness, 2010). In addition, the appearance of
K-complexes is often associated with stage 2 sleep. A K-complex is a very high amplitude pattern of brain
activity that may in some cases occur in response to environmental stimuli. Thus, K-complexes might serve
as a bridge to higher levels of arousal in response to what is going on in our environments (Halász, 1993;
Steriade & Amzica, 1998).

Figure 4.9 Stage 2 sleep is characterized by the appearance of both sleep spindles and K-complexes.

Stage 3 is often referred to as deep sleep or slow-wave sleep because this stage is characterized by low
frequency (less than 3 Hz), high amplitude delta waves (Figure 4.10). During this time, an individual’s
heart rate and respiration slow dramatically. It is much more difficult to awaken someone from sleep
during stage 3 than during earlier stages. Interestingly, individuals who have increased levels of alpha
brain wave activity (more often associated with wakefulness and transition into stage 1 sleep) during stage
3 often report that they do not feel refreshed upon waking, regardless of how long they slept (Stone,
Taylor, McCrae, Kalsekar, & Lichstein, 2008).

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Figure 4.10 (a) Delta waves, which are low frequency and high amplitude, characterize (b) slow-wave stage 3 and
stage 4 sleep.

REM SLEEP

As mentioned earlier, REM sleep is marked by rapid movements of the eyes. The brain waves associated
with this stage of sleep are very similar to those observed when a person is awake, as shown in Figure
4.11, and this is the period of sleep in which dreaming occurs. It is also associated with paralysis of muscle
systems in the body with the exception of those that make circulation and respiration possible. Therefore,
no movement of voluntary muscles occurs during REM sleep in a normal individual; REM sleep is often
referred to as paradoxical sleep because of this combination of high brain activity and lack of muscle tone.
Like NREM sleep, REM has been implicated in various aspects of learning and memory (Wagner, Gais, &
Born, 2001; Siegel, 2001).

Figure 4.11 (a) A period of rapid eye movement is marked by the short red line segment. The brain waves
associated with REM sleep, outlined in the red box in (a), look very similar to those seen (b) during wakefulness.

If people are deprived of REM sleep and then allowed to sleep without disturbance, they will spend more
time in REM sleep in what would appear to be an effort to recoup the lost time in REM. This is known as
the REM rebound, and it suggests that REM sleep is also homeostatically regulated. Aside from the role
that REM sleep may play in processes related to learning and memory, REM sleep may also be involved in
emotional processing and regulation. In such instances, REM rebound may actually represent an adaptive
response to stress in nondepressed individuals by suppressing the emotional salience of aversive events
that occurred in wakefulness (Suchecki, Tiba, & Machado, 2012). Sleep deprivation in general is associated

Chapter 4 | States of Consciousness 127

with a number of negative consequences (Brown, 2012).

The hypnogram below (Figure 4.12) shows a person’s passage through the stages of sleep.

Figure 4.12 A hypnogram is a diagram of the stages of sleep as they occur during a period of sleep. This
hypnogram illustrates how an individual moves through the various stages of sleep.

View this video about the various stages of sleep (http://openstax.org/l/sleepstages) to learn more.

Dreams

Dreams and their associated meanings vary across different cultures and periods of time. By the late
19th century, German psychiatrist Sigmund Freud had become convinced that dreams represented an
opportunity to gain access to the unconscious. By analyzing dreams, Freud thought people could increase
self-awareness and gain valuable insight to help them deal with the problems they faced in their lives.
Freud made distinctions between the manifest content and the latent content of dreams. Manifest content
is the actual content, or storyline, of a dream. Latent content, on the other hand, refers to the hidden
meaning of a dream. For instance, if a woman dreams about being chased by a snake, Freud might have
argued that this represents the woman’s fear of sexual intimacy, with the snake serving as a symbol of a
man’s penis.

Freud was not the only theorist to focus on the content of dreams. The 20th century Swiss psychiatrist Carl
Jung believed that dreams allowed us to tap into the collective unconscious. The collective unconscious,
as described by Jung, is a theoretical repository of information he believed to be shared by everyone.
According to Jung, certain symbols in dreams reflected universal archetypes with meanings that are
similar for all people regardless of culture or location.

The sleep and dreaming researcher Rosalind Cartwright, however, believes that dreams simply reflect life
events that are important to the dreamer. Unlike Freud and Jung, Cartwright’s ideas about dreaming have
found empirical support. For example, she and her colleagues published a study in which women going
through divorce were asked several times over a five month period to report the degree to which their
former spouses were on their minds. These same women were awakened during REM sleep in order to
provide a detailed account of their dream content. There was a significant positive correlation between the
degree to which women thought about their former spouses during waking hours and the number of times

LINK TO LEARNING

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their former spouses appeared as characters in their dreams (Cartwright, Agargun, Kirkby, & Friedman,
2006). Recent research (Horikawa, Tamaki, Miyawaki, & Kamitani, 2013) has uncovered new techniques
by which researchers may effectively detect and classify the visual images that occur during dreaming by
using fMRI for neural measurement of brain activity patterns, opening the way for additional research in
this area.

Alan Hobson, a neuroscientist, is credited for developing activation-synthesis theory of dreaming. Early
versions of this theory proposed that dreams were not the meaning-filled representations of angst
proposed by Freud and others, but were rather the result of our brain attempting to make sense of
(“synthesize”) the neural activity (“activation”) that was happening during REM sleep. Recent adaptations
(e.g., Hobson, 2002) continue to update the theory based on accumulating evidence. For example, Hobson
(2009) suggests that dreaming may represent a state of protoconsciousness. In other words, dreaming
involves constructing a virtual reality in our heads that we might use to help us during wakefulness.
Among a variety of neurobiological evidence, John Hobson cites research on lucid dreams as an
opportunity to better understand dreaming in general. Lucid dreams are dreams in which certain aspects
of wakefulness are maintained during a dream state. In a lucid dream, a person becomes aware of the fact
that they are dreaming, and as such, they can control the dream’s content (LaBerge, 1990).

4.4 Sleep Problems and Disorders

Learning Objectives

By the end of this section, you will be able to:
• Describe the symptoms and treatments of insomnia
• Recognize the symptoms of several parasomnias
• Describe the symptoms and treatments for sleep apnea
• Recognize risk factors associated with sudden infant death syndrome (SIDS) and steps to

prevent it
• Describe the symptoms and treatments for narcolepsy

Many people experience disturbances in their sleep at some point in their lives. Depending on the
population and sleep disorder being studied, between 30% and 50% of the population suffers from a sleep
disorder at some point in their lives (Bixler, Kales, Soldatos, Kaels, & Healey, 1979; Hossain & Shapiro,
2002; Ohayon, 1997, 2002; Ohayon & Roth, 2002). This section will describe several sleep disorders as well
as some of their treatment options.

INSOMNIA

Insomnia, a consistent difficulty in falling or staying asleep, is the most common of the sleep disorders.
Individuals with insomnia often experience long delays between the times that they go to bed and actually
fall asleep. In addition, these individuals may wake up several times during the night only to find that
they have difficulty getting back to sleep. As mentioned earlier, one of the criteria for insomnia involves
experiencing these symptoms for at least three nights a week for at least one month’s time (Roth, 2007).

It is not uncommon for people suffering from insomnia to experience increased levels of anxiety about
their inability to fall asleep. This becomes a self-perpetuating cycle because increased anxiety leads to
increased arousal, and higher levels of arousal make the prospect of falling asleep even more unlikely.
Chronic insomnia is almost always associated with feeling overtired and may be associated with
symptoms of depression.

There may be many factors that contribute to insomnia, including age, drug use, exercise, mental status,
and bedtime routines. Not surprisingly, insomnia treatment may take one of several different approaches.

Chapter 4 | States of Consciousness 129

People who suffer from insomnia might limit their use of stimulant drugs (such as caffeine) or increase
their amount of physical exercise during the day. Some people might turn to over-the-counter (OTC) or
prescribed sleep medications to help them sleep, but this should be done sparingly because many sleep
medications result in dependence and alter the nature of the sleep cycle, and they can increase insomnia
over time. Those who continue to have insomnia, particularly if it affects their quality of life, should seek
professional treatment.

Some forms of psychotherapy, such as cognitive-behavioral therapy, can help sufferers of insomnia.
Cognitive-behavioral therapy is a type of psychotherapy that focuses on cognitive processes and problem
behaviors. The treatment of insomnia likely would include stress management techniques and changes
in problematic behaviors that could contribute to insomnia (e.g., spending more waking time in bed).
Cognitive-behavioral therapy has been demonstrated to be quite effective in treating insomnia (Savard,
Simard, Ivers, & Morin, 2005; Williams, Roth, Vatthauer, & McCrae, 2013).

Solutions to Support Healthy Sleep

Has something like this ever happened to you? My sophomore college housemate got so stressed out during
finals sophomore year he drank almost a whole bottle of Nyquil to try to fall asleep. When he told me, I made
him go see the college therapist.

Many college students struggle getting the recommended 7–9 hours of sleep each night. However, for some,
it’s not because of all-night partying or late-night study sessions. It’s simply that they feel so overwhelmed and
stressed that they cannot fall asleep or stay asleep. One or two nights of sleep difficulty is not unusual, but if
you experience anything more than that, you should seek a doctor’s advice.

Here are some tips to maintain healthy sleep:

• Stick to a sleep schedule, even on the weekends. Try going to bed and waking up at the same time
every day to keep your biological clock in sync so your body gets in the habit of sleeping every night.

• Avoid anything stimulating for an hour before bed. That includes exercise and bright light from devices.

• Exercise daily.

• Avoid naps.

• Keep your bedroom temperature between 60 and 67 degrees. People sleep better in cooler
temperatures.

• Avoid alcohol, cigarettes, caffeine, and heavy meals before bed. It may feel like alcohol helps you
sleep, but it actually disrupts REM sleep and leads to frequent awakenings. Heavy meals may make
you sleepy, but they can also lead to frequent awakenings due to gastric distress.

• If you cannot fall asleep, leave your bed and do something else until you feel tired again. Train your
body to associate the bed with sleeping rather than other activities like studying, eating, or watching
television shows.

PARASOMNIAS

A parasomnia is one of a group of sleep disorders in which unwanted, disruptive motor activity and/
or experiences during sleep play a role. Parasomnias can occur in either REM or NREM phases of sleep.
Sleepwalking, restless leg syndrome, and night terrors are all examples of parasomnias (Mahowald &
Schenck, 2000).

EVERYDAY CONNECTION

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Sleepwalking

In sleepwalking, or somnambulism, the sleeper engages in relatively complex behaviors ranging from
wandering about to driving an automobile. During periods of sleepwalking, sleepers often have their eyes
open, but they are not responsive to attempts to communicate with them. Sleepwalking most often occurs
during slow-wave sleep, but it can occur at any time during a sleep period in some affected individuals
(Mahowald & Schenck, 2000).

Historically, somnambulism has been treated with a variety of pharmacotherapies ranging from
benzodiazepines to antidepressants. However, the success rate of such treatments is questionable.
Guilleminault et al. (2005) found that sleepwalking was not alleviated with the use of benzodiazepines.
However, all of their somnambulistic patients who also suffered from sleep-related breathing problems
showed a marked decrease in sleepwalking when their breathing problems were effectively treated.

A Sleepwalking Defense?

On January 16, 1997, Scott Falater sat down to dinner with his wife and children and told them about difficulties
he was experiencing on a project at work. After dinner, he prepared some materials to use in leading a church
youth group the following morning, and then he attempted to repair the family’s swimming pool pump before
retiring to bed. The following morning, he awoke to barking dogs and unfamiliar voices from downstairs. As
he went to investigate what was going on, he was met by a group of police officers who arrested him for the
murder of his wife (Cartwright, 2004; CNN, 1999).

Yarmila Falater’s body was found in the family’s pool with 44 stab wounds. A neighbor called the police after
witnessing Falater standing over his wife’s body before dragging her into the pool. Upon a search of the
premises, police found blood-stained clothes and a bloody knife in the trunk of Falater’s car, and he had blood
stains on his neck.

Remarkably, Falater insisted that he had no recollection of hurting his wife in any way. His children and his
wife’s parents all agreed that Falater had an excellent relationship with his wife and they couldn’t think of a
reason that would provide any sort of motive to murder her (Cartwright, 2004).

Scott Falater had a history of regular episodes of sleepwalking as a child, and he had even behaved violently
toward his sister once when she tried to prevent him from leaving their home in his pajamas during a
sleepwalking episode. He suffered from no apparent anatomical brain anomalies or psychological disorders. It
appeared that Scott Falater had killed his wife in his sleep, or at least, that is the defense he used when he
was tried for his wife’s murder (Cartwright, 2004; CNN, 1999). In Falater’s case, a jury found him guilty of first
degree murder in June of 1999 (CNN, 1999); however, there are other murder cases where the sleepwalking
defense has been used successfully. As scary as it sounds, many sleep researchers believe that homicidal
sleepwalking is possible in individuals suffering from the types of sleep disorders described below (Broughton
et al., 1994; Cartwright, 2004; Mahowald, Schenck, & Cramer Bornemann, 2005; Pressman, 2007).

REM Sleep Behavior Disorder (RBD)

REM sleep behavior disorder (RBD) occurs when the muscle paralysis associated with the REM sleep
phase does not occur. Individuals who suffer from RBD have high levels of physical activity during REM
sleep, especially during disturbing dreams. These behaviors vary widely, but they can include kicking,
punching, scratching, yelling, and behaving like an animal that has been frightened or attacked. People
who suffer from this disorder can injure themselves or their sleeping partners when engaging in these
behaviors. Furthermore, these types of behaviors ultimately disrupt sleep, although affected individuals
have no memories that these behaviors have occurred (Arnulf, 2012).

This disorder is associated with a number of neurodegenerative diseases such as Parkinson’s disease. In
fact, this relationship is so robust that some view the presence of RBD as a potential aid in the diagnosis

DIG DEEPER

Chapter 4 | States of Consciousness 131

and treatment of a number of neurodegenerative diseases (Ferini-Strambi, 2011). Clonazepam, an anti-
anxiety medication with sedative properties, is most often used to treat RBD. It is administered alone or
in conjunction with doses of melatonin (the hormone secreted by the pineal gland). As part of treatment,
the sleeping environment is often modified to make it a safer place for those suffering from RBD (Zangini,
Calandra-Buonaura, Grimaldi, & Cortelli, 2011).

Other Parasomnias

A person with restless leg syndrome has uncomfortable sensations in the legs during periods of inactivity
or when trying to fall asleep. This discomfort is relieved by deliberately moving the legs, which, not
surprisingly, contributes to difficulty in falling or staying asleep. Restless leg syndrome is quite common
and has been associated with a number of other medical diagnoses, such as chronic kidney disease and
diabetes (Mahowald & Schenck, 2000). There are a variety of drugs that treat restless leg syndrome:
benzodiazepines, opiates, and anticonvulsants (Restless Legs Syndrome Foundation, n.d.).

Night terrors result in a sense of panic in the sufferer and are often accompanied by screams and attempts
to escape from the immediate environment (Mahowald & Schenck, 2000). Although individuals suffering
from night terrors appear to be awake, they generally have no memories of the events that occurred, and
attempts to console them are ineffective. Typically, individuals suffering from night terrors will fall back
asleep again within a short time. Night terrors apparently occur during the NREM phase of sleep (Provini,
Tinuper, Bisulli, & Lagaresi, 2011). Generally, treatment for night terrors is unnecessary unless there is
some underlying medical or psychological condition that is contributing to the night terrors (Mayo Clinic,
n.d.).

SLEEP APNEA

Sleep apnea is defined by episodes during which a sleeper’s breathing stops. These episodes can last 10–20
seconds or longer and often are associated with brief periods of arousal. While individuals suffering from
sleep apnea may not be aware of these repeated disruptions in sleep, they do experience increased levels of
fatigue. Many individuals diagnosed with sleep apnea first seek treatment because their sleeping partners
indicate that they snore loudly and/or stop breathing for extended periods of time while sleeping (Henry
& Rosenthal, 2013). Sleep apnea is much more common in overweight people and is often associated
with loud snoring. Surprisingly, sleep apnea may exacerbate cardiovascular disease (Sánchez-de-la-Torre,
Campos-Rodriguez, & Barbé, 2012). While sleep apnea is less common in thin people, anyone, regardless
of their weight, who snores loudly or gasps for air while sleeping, should be checked for sleep apnea.

While people are often unaware of their sleep apnea, they are keenly aware of some of the adverse
consequences of insufficient sleep. Consider a patient who believed that as a result of his sleep apnea he
“had three car accidents in six weeks. They were ALL my fault. Two of them I didn’t even know I was
involved in until afterwards” (Henry & Rosenthal, 2013, p. 52). It is not uncommon for people suffering
from undiagnosed or untreated sleep apnea to fear that their careers will be affected by the lack of sleep,
illustrated by this statement from another patient, “I’m in a job where there’s a premium on being mentally
alert. I was really sleepy… and having trouble concentrating…. It was getting to the point where it was
kind of scary” (Henry & Rosenthal, 2013, p. 52).

There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea. Obstructive sleep
apnea occurs when an individual’s airway becomes blocked during sleep, and air is prevented from
entering the lungs. In central sleep apnea, disruption in signals sent from the brain that regulate breathing
cause periods of interrupted breathing (White, 2005).

One of the most common treatments for sleep apnea involves the use of a special device during sleep.
A continuous positive airway pressure (CPAP) device includes a mask that fits over the sleeper’s nose
and mouth, which is connected to a pump that pumps air into the person’s airways, forcing them to
remain open, as shown in Figure 4.13. Some newer CPAP masks are smaller and cover only the nose.
This treatment option has proven to be effective for people suffering from mild to severe cases of sleep

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apnea (McDaid et al., 2009). However, alternative treatment options are being explored because consistent
compliance by users of CPAP devices is a problem. Recently, a new EPAP (expiratory positive air pressure)
device has shown promise in double-blind trials as one such alternative (Berry, Kryger, & Massie, 2011).

Figure 4.13 (a) A typical CPAP device used in the treatment of sleep apnea is (b) affixed to the head with straps,
and a mask that covers the nose and mouth.

SIDS

In sudden infant death syndrome (SIDS) an infant stops breathing during sleep and dies. Infants younger
than 12 months appear to be at the highest risk for SIDS, and boys have a greater risk than girls. A number
of risk factors have been associated with SIDS including premature birth, smoking within the home, and
hyperthermia. There may also be differences in both brain structure and function in infants that die from
SIDS (Berkowitz, 2012; Mage & Donner, 2006; Thach, 2005).

The substantial amount of research on SIDS has led to a number of recommendations to parents to protect
their children (Figure 4.14). For one, research suggests that infants should be placed on their backs when
put down to sleep, and their cribs should not contain any items which pose suffocation threats, such as
blankets, pillows or padded crib bumpers (cushions that cover the bars of a crib). Infants should not have
caps placed on their heads when put down to sleep in order to prevent overheating, and people in the
child’s household should abstain from smoking in the home. Recommendations like these have helped
to decrease the number of infant deaths from SIDS in recent years (Mitchell, 2009; Task Force on Sudden
Infant Death Syndrome, 2011).

Figure 4.14 The Safe to Sleep campaign educates the public about how to minimize risk factors associated with
SIDS. This campaign is sponsored in part by the National Institute of Child Health and Human Development.

NARCOLEPSY

Unlike the other sleep disorders described in this section, a person with narcolepsy cannot resist falling
asleep at inopportune times. These sleep episodes are often associated with cataplexy, which is a lack of
muscle tone or muscle weakness, and in some cases involves complete paralysis of the voluntary muscles.
This is similar to the kind of paralysis experienced by healthy individuals during REM sleep (Burgess
& Scammell, 2012; Hishikawa & Shimizu, 1995; Luppi et al., 2011). Narcoleptic episodes take on other
features of REM sleep. For example, around one third of individuals diagnosed with narcolepsy experience
vivid, dream-like hallucinations during narcoleptic attacks (Chokroverty, 2010).

Surprisingly, narcoleptic episodes are often triggered by states of heightened arousal or stress. The typical

Chapter 4 | States of Consciousness 133

episode can last from a minute or two to half an hour. Once awakened from a narcoleptic attack, people
report that they feel refreshed (Chokroverty, 2010). Obviously, regular narcoleptic episodes could interfere
with the ability to perform one’s job or complete schoolwork, and in some situations, narcolepsy can result
in significant harm and injury (e.g., driving a car or operating machinery or other potentially dangerous
equipment).

Generally, narcolepsy is treated using psychomotor stimulant drugs, such as amphetamines (Mignot,
2012). These drugs promote increased levels of neural activity. Narcolepsy is associated with reduced
levels of the signaling molecule hypocretin in some areas of the brain (De la Herrán-Arita & Drucker-Colín,
2012; Han, 2012), and the traditional stimulant drugs do not have direct effects on this system. Therefore,
it is quite likely that new medications that are developed to treat narcolepsy will be designed to target the
hypocretin system.

There is a tremendous amount of variability among sufferers, both in terms of how symptoms of
narcolepsy manifest and the effectiveness of currently available treatment options. This is illustrated by
McCarty’s (2010) case study of a 50-year-old woman who sought help for the excessive sleepiness during
normal waking hours that she had experienced for several years. She indicated that she had fallen asleep
at inappropriate or dangerous times, including while eating, while socializing with friends, and while
driving her car. During periods of emotional arousal, the woman complained that she felt some weakness
in the right side of her body. Although she did not experience any dream-like hallucinations, she was
diagnosed with narcolepsy as a result of sleep testing. In her case, the fact that her cataplexy was confined
to the right side of her body was quite unusual. Early attempts to treat her condition with a stimulant
drug alone were unsuccessful. However, when a stimulant drug was used in conjunction with a popular
antidepressant, her condition improved dramatically.

4.5 Substance Use and Abuse

Learning Objectives

By the end of this section, you will be able to:
• Describe the diagnostic criteria for substance use disorders
• Identify the neurotransmitter systems impacted by various categories of drugs
• Describe how different categories of drugs affect behavior and experience

While we all experience altered states of consciousness in the form of sleep on a regular basis, some
people use drugs and other substances that result in altered states of consciousness as well. This section
will present information relating to the use of various psychoactive drugs and problems associated with
such use. This will be followed by brief descriptions of the effects of some of the more well-known drugs
commonly used today.

SUBSTANCE USE DISORDERS

The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) is used by
clinicians to diagnose individuals suffering from various psychological disorders. Drug use disorders are
addictive disorders, and the criteria for specific substance (drug) use disorders are described in DSM-5. A
person who has a substance use disorder often uses more of the substance than they originally intended to
and continues to use that substance despite experiencing significant adverse consequences. In individuals
diagnosed with a substance use disorder, there is a compulsive pattern of drug use that is often associated
with both physical and psychological dependence.

Physical dependence involves changes in normal bodily functions—the user will experience withdrawal
from the drug upon cessation of use. In contrast, a person who has psychological dependence has an

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emotional, rather than physical, need for the drug and may use the drug to relieve psychological distress.
Tolerance is linked to physiological dependence, and it occurs when a person requires more and more
drug to achieve effects previously experienced at lower doses. Tolerance can cause the user to increase the
amount of drug used to a dangerous level—even to the point of overdose and death.

Drug withdrawal includes a variety of negative symptoms experienced when drug use is discontinued.
These symptoms usually are opposite of the effects of the drug. For example, withdrawal from sedative
drugs often produces unpleasant arousal and agitation. In addition to withdrawal, many individuals who
are diagnosed with substance use disorders will also develop tolerance to these substances. Psychological
dependence, or drug craving, is a recent addition to the diagnostic criteria for substance use disorder in
DSM-5. This is an important factor because we can develop tolerance and experience withdrawal from any
number of drugs that we do not abuse. In other words, physical dependence in and of itself is of limited
utility in determining whether or not someone has a substance use disorder.

DRUG CATEGORIES

The effects of all psychoactive drugs occur through their interactions with our endogenous
neurotransmitter systems. Many of these drugs, and their relationships, are shown in Table 4.2. As you
have learned, drugs can act as agonists or antagonists of a given neurotransmitter system. An agonist
facilitates the activity of a neurotransmitter system, and antagonists impede neurotransmitter activity.

Drugs and Their Effects

Class of Drug Examples
Effects on
the Body

Effects When Used
Psychologically
Addicting?

Stimulants Cocaine,
amphetamines
(including some
ADHD medications
such as Adderall),
methamphetamines,
MDMA (“Ecstasy”
or “Molly”)

Increased
heart rate,
blood
pressure,
body
temperature

Increased alertness,
mild euphoria,
decreased appetite in
low doses. High
doses increase
agitation, paranoia,
can cause
hallucinations. Some
can cause heightened
sensitivity to physical
stimuli. High doses
of MDMA can cause
brain toxicity and
death.

Yes

Sedative-
Hypnotics
(“Depressants”)

Alcohol,
barbiturates (e.g.,
secobarbital,
pentobarbital),
Benzodiazepines
(e.g., Xanax)

Decreased
heart rate,
blood
pressure

Low doses increase
relaxation, decrease
inhibitions. High
doses can induce
sleep, cause motor
disturbance, memory
loss, decreased
respiratory function,
and death.

Yes

Chapter 4 | States of Consciousness 135

Drugs and Their Effects

Class of Drug Examples
Effects on
the Body

Effects When Used
Psychologically
Addicting?

Opiates Opium, Heroin,
Fentanyl, Morphine,
Oxycodone,
Vicoden,
methadone, and
other prescription
pain relievers

Decreased
pain, pupil
dilation,
decreased
gut
motility,
decreased
respiratory
function

Pain relief, euphoria,
sleepiness. High
doses can cause
death due to
respiratory
depression.

Yes

Hallucinogens Marijuana, LSD,
Peyote, mescaline,
DMT, dissociative
anesthetics
including ketamine
and PCP

Increased
heart rate
and blood
pressure
that may
dissipate
over time

Mild to intense
perceptual changes
with high variability
in effects based on
strain, method of
ingestion, and
individual
differences

Yes

Table 4.2

Alcohol and Other Depressants

Ethanol, which we commonly refer to as alcohol, is in a class of psychoactive drugs known as depressants
(Figure 4.15). A depressant is a drug that tends to suppress central nervous system activity. Other
depressants include barbiturates and benzodiazepines. These drugs share in common their ability to serve
as agonists of the gamma-Aminobutyric acid (GABA) neurotransmitter system. Because GABA has a
quieting effect on the brain, GABA agonists also have a quieting effect; these types of drugs are often
prescribed to treat both anxiety and insomnia.

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Figure 4.15 The GABA-gated chloride (Cl–) channel is embedded in the cell membrane of certain neurons. The
channel has multiple receptor sites where alcohol, barbiturates, and benzodiazepines bind to exert their effects. The
binding of these molecules opens the chloride channel, allowing negatively-charged chloride ions (Cl–) into the
neuron’s cell body. Changing its charge in a negative direction pushes the neuron away from firing; thus, activating a
GABA neuron has a quieting effect on the brain.

Acute alcohol administration results in a variety of changes to consciousness. At rather low doses, alcohol
use is associated with feelings of euphoria. As the dose increases, people report feeling sedated. Generally,
alcohol is associated with decreases in reaction time and visual acuity, lowered levels of alertness, and
reduction in behavioral control. With excessive alcohol use, a person might experience a complete loss of
consciousness and/or difficulty remembering events that occurred during a period of intoxication (McKim
& Hancock, 2013). In addition, if a pregnant woman consumes alcohol, her infant may be born with a
cluster of birth defects and symptoms collectively called fetal alcohol spectrum disorder (FASD) or fetal
alcohol syndrome (FAS).

With repeated use of many central nervous system depressants, such as alcohol, a person becomes
physically dependent upon the substance and will exhibit signs of both tolerance and withdrawal.
Psychological dependence on these drugs is also possible. Therefore, the abuse potential of central nervous
system depressants is relatively high.

Drug withdrawal is usually an aversive experience, and it can be a life-threatening process in individuals
who have a long history of very high doses of alcohol and/or barbiturates. This is of such concern
that people who are trying to overcome addiction to these substances should only do so under medical
supervision.

Stimulants

Stimulants are drugs that tend to increase overall levels of neural activity. Many of these drugs act as
agonists of the dopamine neurotransmitter system. Dopamine activity is often associated with reward
and craving; therefore, drugs that affect dopamine neurotransmission often have abuse liability. Drugs in

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this category include cocaine, amphetamines (including methamphetamine), cathinones (i.e., bath salts),
MDMA (ecstasy), nicotine, and caffeine.

Cocaine can be taken in multiple ways. While many users snort cocaine, intravenous injection and
inhalation (smoking) are also common. The freebase version of cocaine, known as crack, is a potent,
smokable version of the drug. Like many other stimulants, cocaine agonizes the dopamine
neurotransmitter system by blocking the reuptake of dopamine in the neuronal synapse.

Methamphetamine

Methamphetamine in its smokable form, often called “crystal meth” due to its resemblance to rock crystal
formations, is highly addictive. The smokable form reaches the brain very quickly to produce an intense
euphoria that dissipates almost as fast as it arrives, prompting users to continuing taking the drug. Users often
consume the drug every few hours across days-long binges called “runs,” in which the user forgoes food and
sleep. In the wake of the opiate epidemic, many drug cartels in Mexico are shifting from producing heroin
to producing highly potent but inexpensive forms of methamphetamine. The low cost coupled with lower risk
of overdose than with opiate drugs is making crystal meth a popular choice among drug users today (NIDA,
2019). Using crystal meth poses a number of serious long-term health issues, including dental problems (often
called “meth mouth”), skin abrasions caused by excessive scratching, memory loss, sleep problems, violent
behavior, paranoia, and hallucinations. Methamphetamine addiction produces an intense craving that is difficult
to treat.

Amphetamines have a mechanism of action quite similar to cocaine in that they block the reuptake of
dopamine in addition to stimulating its release (Figure 4.16). While amphetamines are often abused, they
are also commonly prescribed to children diagnosed with attention deficit hyperactivity disorder (ADHD).
It may seem counterintuitive that stimulant medications are prescribed to treat a disorder that involves
hyperactivity, but the therapeutic effect comes from increases in neurotransmitter activity within certain
areas of the brain associated with impulse control. These brain areas include the prefrontal cortex and basal
ganglia.

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Figure 4.16 As one of their mechanisms of action, cocaine and amphetamines block the reuptake of dopamine from
the synapse into the presynaptic cell.

In recent years, methamphetamine (meth) use has become increasingly widespread. Methamphetamine
is a type of amphetamine that can be made from ingredients that are readily available (e.g., medications
containing pseudoephedrine, a compound found in many over-the-counter cold and flu remedies).
Despite recent changes in laws designed to make obtaining pseudoephedrine more difficult,
methamphetamine continues to be an easily accessible and relatively inexpensive drug option (Shukla,
Crump, & Chrisco, 2012).

Stimulant users seek a euphoric high, feelings of intense elation and pleasure, especially in those users
who take the drug via intravenous injection or smoking. MDMA (3.4-methelynedioxy-methamphetamine,
commonly known as “ecstasy” or “Molly”) is a mild stimulant with perception-altering effects. It is typically
consumed in pill form. Users experience increased energy, feelings of pleasure, and emotional warmth.
Repeated use of these stimulants can have significant adverse consequences. Users can experience physical
symptoms that include nausea, elevated blood pressure, and increased heart rate. In addition, these
drugs can cause feelings of anxiety, hallucinations, and paranoia (Fiorentini et al., 2011). Normal brain
functioning is altered after repeated use of these drugs. For example, repeated use can lead to overall
depletion among the monoamine neurotransmitters (dopamine, norepinephrine, and serotonin).
Depletion of certain neurotransmitters can lead to mood dysphoria, cognitive problems, and other factors.
This can lead to people compulsively using stimulants such as cocaine and amphetamines, in part to try
to reestablish the person’s physical and psychological pre-use baseline. (Jayanthi & Ramamoorthy, 2005;
Rothman, Blough, & Baumann, 2007).

Caffeine is another stimulant drug. While it is probably the most commonly used drug in the world, the
potency of this particular drug pales in comparison to the other stimulant drugs described in this section.
Generally, people use caffeine to maintain increased levels of alertness and arousal. Caffeine is found in
many common medicines (such as weight loss drugs), beverages, foods, and even cosmetics (Herman &
Herman, 2013). While caffeine may have some indirect effects on dopamine neurotransmission, its primary
mechanism of action involves antagonizing adenosine activity (Porkka-Heiskanen, 2011). Adenosine is

Chapter 4 | States of Consciousness 139

a neurotransmitter that promotes sleep. Caffeine is an adenosine antagonist, so caffeine inhibits the
adenosine receptors, thus decreasing sleepiness and promoting wakefulness.

While caffeine is generally considered a relatively safe drug, high blood levels of caffeine can result
in insomnia, agitation, muscle twitching, nausea, irregular heartbeat, and even death (Reissig, Strain, &
Griffiths, 2009; Wolt, Ganetsky, & Babu, 2012). In 2012, Kromann and Nielson reported on a case study of
a 40-year-old woman who suffered significant ill effects from her use of caffeine. The woman used caffeine
in the past to boost her mood and to provide energy, but over the course of several years, she increased
her caffeine consumption to the point that she was consuming three liters of soda each day. Although she
had been taking a prescription antidepressant, her symptoms of depression continued to worsen and she
began to suffer physically, displaying significant warning signs of cardiovascular disease and diabetes.
Upon admission to an outpatient clinic for treatment of mood disorders, she met all of the diagnostic
criteria for substance dependence and was advised to dramatically limit her caffeine intake. Once she was
able to limit her use to less than 12 ounces of soda a day, both her mental and physical health gradually
improved. Despite the prevalence of caffeine use and the large number of people who confess to suffering
from caffeine addiction, this was the first published description of soda dependence appearing in scientific
literature.

Nicotine is highly addictive, and the use of tobacco products is associated with increased risks of heart
disease, stroke, and a variety of cancers. Nicotine exerts its effects through its interaction with acetylcholine
receptors. Acetylcholine functions as a neurotransmitter in motor neurons. In the central nervous system,
it plays a role in arousal and reward mechanisms. Nicotine is most commonly used in the form of
tobacco products like cigarettes or chewing tobacco; therefore, there is a tremendous interest in developing
effective smoking cessation techniques. To date, people have used a variety of nicotine replacement
therapies in addition to various psychotherapeutic options in an attempt to discontinue their use of
tobacco products. In general, smoking cessation programs may be effective in the short term, but it is
unclear whether these effects persist (Cropley, Theadom, Pravettoni, & Webb, 2008; Levitt, Shaw, Wong, &
Kaczorowski, 2007; Smedslund, Fisher, Boles, & Lichtenstein, 2004). Vaping as a means to deliver nicotine
is becoming increasingly popular, especially among teens and young adults. Vaping uses battery-powered
devices, sometimes called e-cigarettes, that deliver liquid nicotine and flavorings as a vapor. Originally
reported as a safe alternative to the known cancer-causing agents found in cigarettes, vaping is now known
to be very dangerous and has led to serious lung disease and death in users.

Opioids

An opioid is one of a category of drugs that includes heroin, morphine, methadone, and codeine. Opioids
have analgesic properties; that is, they decrease pain. Humans have an endogenous opioid
neurotransmitter system—the body makes small quantities of opioid compounds that bind to opioid
receptors reducing pain and producing euphoria. Thus, opioid drugs, which mimic this endogenous
painkilling mechanism, have an extremely high potential for abuse. Natural opioids, called opiates, are
derivatives of opium, which is a naturally occurring compound found in the poppy plant. There are
now several synthetic versions of opiate drugs (correctly called opioids) that have very potent painkilling
effects, and they are often abused. For example, the National Institutes of Drug Abuse has sponsored
research that suggests the misuse and abuse of the prescription pain killers hydrocodone and oxycodone
are significant public health concerns (Maxwell, 2006). In 2013, the U.S. Food and Drug Administration
recommended tighter controls on their medical use.

Historically, heroin has been a major opioid drug of abuse (Figure 4.17). Heroin can be snorted, smoked,
or injected intravenously. Heroin produces intense feelings of euphoria and pleasure, which are amplified
when the heroin is injected intravenously. Following the initial “rush,” users experience 4–6 hours of “going
on the nod,” alternating between conscious and semiconscious states. Heroin users often shoot the drug
directly into their veins. Some people who have injected many times into their arms will show “track
marks,” while other users will inject into areas between their fingers or between their toes, so as not to
show obvious track marks and, like all abusers of intravenous drugs, have an increased risk for contraction

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of both tuberculosis and HIV.

Figure 4.17 (a) Common paraphernalia for heroin preparation and use are shown here in a needle exchange kit. (b)
Heroin is cooked on a spoon over a candle. (credit a: modification of work by Todd Huffman)

Aside from their utility as analgesic drugs, opioid-like compounds are often found in cough suppressants,
anti-nausea, and anti-diarrhea medications. Given that withdrawal from a drug often involves an
experience opposite to the effect of the drug, it should be no surprise that opioid withdrawal resembles
a severe case of the flu. While opioid withdrawal can be extremely unpleasant, it is not life-threatening
(Julien, 2005). Still, people experiencing opioid withdrawal may be given methadone to make withdrawal
from the drug less difficult. Methadone is a synthetic opioid that is less euphorigenic than heroin and
similar drugs. Methadone clinics help people who previously struggled with opioid addiction manage
withdrawal symptoms through the use of methadone. Other drugs, including the opioid buprenorphine,
have also been used to alleviate symptoms of opiate withdrawal.

Codeine is an opioid with relatively low potency. It is often prescribed for minor pain, and it is available
over-the-counter in some other countries. Like all opioids, codeine does have abuse potential. In fact, abuse
of prescription opioid medications is becoming a major concern worldwide (Aquina, Marques-Baptista,
Bridgeman, & Merlin, 2009; Casati, Sedefov, & Pfeiffer-Gerschel, 2012).

The Opioid Crisis

Few people in the United States remain untouched by the recent opioid epidemic. It seems like everyone
knows a friend, family member, or neighbor who has died of an overdose. Opioid addiction reached crisis levels
in the United States such that by 2019, an average of 130 people died each day of an opioid overdose (NIDA,
2019).

The crisis actually began in the 1990s, when pharmaceutical companies began mass-marketing pain-relieving
opioid drugs like OxyContin with the promise (now known to be false) that they were non-addictive. Increased
prescriptions led to greater rates of misuse, along with greater incidence of addiction, even among patients
who used these drugs as prescribed. Physiologically, the body can become addicted to opiate drugs in less
than a week, including when taken as prescribed. Withdrawal from opioids includes pain, which patients often
misinterpret as pain caused by the problem that led to the original prescription, and which motivates patients
to continue using the drugs.

The FDA’s 2013 recommendation for tighter controls on opiate prescriptions left many patients addicted to
prescription drugs like OxyContin unable to obtain legitimate prescriptions. This created a black market for
the drug, where prices soared to $80 or more for a single pill. To prevent withdrawal, many people turned to
cheaper heroin, which could be bought for $5 a dose or less. To keep heroin affordable, many dealers began
adding more potent synthetic opioids including fentanyl and carfentanyl to increase the effects of heroin. These
synthetic drugs are so potent that even small doses can cause overdose and death.

EVERYDAY CONNECTION

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Large-scale public health campaigns by the National Institutes of Health and the National Institute of Drug
Abuse have led to recent declines in the opioid crisis. These initiatives include increasing access to treatment
and recovery services, increasing access to overdose-reversal drugs like Naloxone, and implementing better
public health monitoring systems (NIDA, 2019).

Hallucinogens

A hallucinogen is one of a class of drugs that results in profound alterations in sensory and perceptual
experiences (Figure 4.18). In some cases, users experience vivid visual hallucinations. It is also common
for these types of drugs to cause hallucinations of body sensations (e.g., feeling as if you are a giant) and a
skewed perception of the passage of time.

Figure 4.18 Psychedelic images like this are often associated with hallucinogenic compounds. (credit: modification
of work by “new 1lluminati”/Flickr)

As a group, hallucinogens are incredibly varied in terms of the neurotransmitter systems they affect.
Mescaline and LSD are serotonin agonists, and PCP (angel dust) and ketamine (an animal anesthetic) act
as antagonists of the NMDA glutamate receptor. In general, these drugs are not thought to possess the
same sort of abuse potential as other classes of drugs discussed in this section.

To learn more about some of the most commonly abused prescription and street drugs, check out the
Commonly Abused Drugs Chart (http://openstax.org/l/drugabuse) and the Commonly Abused
Prescription Drugs Chart (http://openstax.org/l/Rxabuse) from the National Institute on Drug Abuse.

Medical Marijuana

The decade from 2010–2019 brought many changes in laws regarding marijuana. While the possession and
use of marijuana remains illegal in many states, it is now legal to possess limited quantities of marijuana
for recreational use in eleven states: Alaska, California, Colorado, Illinois, Maine, Massachusetts, Michigan,
Nevada, Oregon, Vermont, and Washington. Medical marijuana is legal in over half of the United States and
in the District of Columbia (Figure 4.19). Medical marijuana is marijuana that is prescribed by a doctor for
the treatment of a health condition. For example, people who undergo chemotherapy will often be prescribed

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marijuana to stimulate their appetites and prevent excessive weight loss resulting from the side effects of
chemotherapy treatment. Marijuana may also have some promise in the treatment of a variety of medical
conditions (Mather, Rauwendaal, Moxham-Hall, & Wodak, 2013; Robson, 2014; Schicho & Storr, 2014).

Figure 4.19 Medical marijuana shops are becoming more and more common in the United States. (credit:
Laurie Avocado)

While medical marijuana laws have been passed on a state-by-state basis, federal laws still classify this as
an illicit substance, making conducting research on the potentially beneficial medicinal uses of marijuana
problematic. There is quite a bit of controversy within the scientific community as to the extent to which
marijuana might have medicinal benefits due to a lack of large-scale, controlled research (Bostwick, 2012). As
a result, many scientists have urged the federal government to allow for relaxation of current marijuana laws
and classifications in order to facilitate a more widespread study of the drug’s effects (Aggarwal et al., 2009;
Bostwick, 2012; Kogan & Mechoulam, 2007).

Until recently, the United States Department of Justice routinely arrested people involved and seized marijuana
used in medicinal settings. In the latter part of 2013, however, the United States Department of Justice issued
statements indicating that they would not continue to challenge state medical marijuana laws. This shift in
policy may be in response to the scientific community’s recommendations and/or reflect changing public
opinion regarding marijuana.

4.6 Other States of Consciousness

Learning Objectives

By the end of this section, you will be able to:
• Define hypnosis and meditation
• Understand the similarities and differences of hypnosis and meditation

Our states of consciousness change as we move from wakefulness to sleep. We also alter our consciousness
through the use of various psychoactive drugs. This final section will consider hypnotic and meditative
states as additional examples of altered states of consciousness experienced by some individuals.

HYPNOSIS

Hypnosis is a state of extreme self-focus and attention in which minimal attention is given to external
stimuli. In the therapeutic setting, a clinician may use relaxation and suggestion in an attempt to alter the
thoughts and perceptions of a patient. Hypnosis has also been used to draw out information believed to be
buried deeply in someone’s memory. For individuals who are especially open to the power of suggestion,
hypnosis can prove to be a very effective technique, and brain imaging studies have demonstrated
that hypnotic states are associated with global changes in brain functioning (Del Casale et al., 2012;
Guldenmund, Vanhaudenhuyse, Boly, Laureys, & Soddu, 2012).

Historically, hypnosis has been viewed with some suspicion because of its portrayal in popular media

Chapter 4 | States of Consciousness 143

and entertainment (Figure 4.20). Therefore, it is important to make a distinction between hypnosis as
an empirically based therapeutic approach versus as a form of entertainment. Contrary to popular belief,
individuals undergoing hypnosis usually have clear memories of the hypnotic experience and are in
control of their own behaviors. While hypnosis may be useful in enhancing memory or a skill, such
enhancements are very modest in nature (Raz, 2011).

Figure 4.20 Popular portrayals of hypnosis have led to some widely-held misconceptions.

How exactly does a hypnotist bring a participant to a state of hypnosis? While there are variations, there
are four parts that appear consistent in bringing people into the state of suggestibility associated with
hypnosis (National Research Council, 1994). These components include:

• The participant is guided to focus on one thing, such as the hypnotist’s words or a ticking watch.

• The participant is made comfortable and is directed to be relaxed and sleepy.

• The participant is told to be open to the process of hypnosis, trust the hypnotist and let go.

• The participant is encouraged to use his or her imagination.

These steps are conducive to being open to the heightened suggestibility of hypnosis.

People vary in terms of their ability to be hypnotized, but a review of available research suggests that
most people are at least moderately hypnotizable (Kihlstrom, 2013). Hypnosis in conjunction with other
techniques is used for a variety of therapeutic purposes and has shown to be at least somewhat effective
for pain management, treatment of depression and anxiety, smoking cessation, and weight loss (Alladin,
2012; Elkins, Johnson, & Fisher, 2012; Golden, 2012; Montgomery, Schnur, & Kravits, 2012).

How does hypnosis work? Two theories attempt to answer this question: One theory views hypnosis as
dissociation and the other theory views it as the performance of a social role. According to the dissociation
view, hypnosis is effectively a dissociated state of consciousness, much like our earlier example where you
may drive to work, but you are only minimally aware of the process of driving because your attention
is focused elsewhere. This theory is supported by Ernest Hilgard’s research into hypnosis and pain. In
Hilgard’s experiments, he induced participants into a state of hypnosis, and placed their arms into ice
water. Participants were told they would not feel pain, but they could press a button if they did; while they
reported not feeling pain, they did, in fact, press the button, suggesting a dissociation of consciousness
while in the hypnotic state (Hilgard & Hilgard, 1994).

Taking a different approach to explain hypnosis, the social-cognitive theory of hypnosis sees people

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in hypnotic states as performing the social role of a hypnotized person. As you will learn when you
study social roles, people’s behavior can be shaped by their expectations of how they should act in
a given situation. Some view a hypnotized person’s behavior not as an altered or dissociated state of
consciousness, but as their fulfillment of the social expectations for that role (Coe, 2009; Coe & Sarbin,
1966).

MEDITATION

Meditation is the act of focusing on a single target (such as the breath or a repeated sound) to increase
awareness of the moment. While hypnosis is generally achieved through the interaction of a therapist and
the person being treated, an individual can perform meditation alone. Often, however, people wishing to
learn to meditate receive some training in techniques to achieve a meditative state.

Although there are a number of different techniques in use, the central feature of all meditation is clearing
the mind in order to achieve a state of relaxed awareness and focus (Chen et al., 2013; Lang et al.,
2012). Mindfulness meditation has recently become popular. In the variation of mindful meditation, the
meditator’s attention is focused on some internal process or an external object (Zeidan, Grant, Brown,
McHaffie, & Coghill, 2012).

Meditative techniques have their roots in religious practices (Figure 4.21), but their use has grown in
popularity among practitioners of alternative medicine. Research indicates that meditation may help
reduce blood pressure, and the American Heart Association suggests that meditation might be used in
conjunction with more traditional treatments as a way to manage hypertension, although there is not
sufficient data for a recommendation to be made (Brook et al., 2013). Like hypnosis, meditation also
shows promise in stress management, sleep quality (Caldwell, Harrison, Adams, Quin, & Greeson, 2010),
treatment of mood and anxiety disorders (Chen et al., 2013; Freeman et al., 2010; Vøllestad, Nielsen, &
Nielsen, 2012), and pain management (Reiner, Tibi, & Lipsitz, 2013).

Figure 4.21 (a) This is a statue of a meditating Buddha, representing one of the many religious traditions of which
meditation plays a part. (b) People practicing meditation may experience an alternate state of consciousness. (credit
a: modification of work by Jim Epler; credit b: modification of work by Caleb Roenigk)

Feeling stressed? Think meditation might help? Watch this instructional video about using Buddhist
meditation techniques to alleviate stress (http://openstax.org/l/meditate) to learn more.

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Watch this video about the results of a brain imaging study in individuals who underwent specific
mindfulness meditative techniques (http://openstax.org/l/brainimaging) to learn more.

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alpha wave

biological rhythm

cataplexy

central sleep apnea

circadian rhythm

codeine

cognitive-behavioral therapy

collective unconscious

consciousness

continuous positive airway pressure (CPAP)

delta wave

depressant

euphoric high

evolutionary psychology

hallucinogen

homeostasis

hypnosis

insomnia

jet lag

K-complex

latent content

lucid dream

Key Terms

type of relatively low frequency, relatively high amplitude brain wave that becomes
synchronized; characteristic of the beginning of stage 1 sleep

internal cycle of biological activity

lack of muscle tone or muscle weakness, and in some cases complete paralysis of the voluntary
muscles

sleep disorder with periods of interrupted breathing due to a disruption in signals
sent from the brain that regulate breathing

biological rhythm that occurs over approximately 24 hours

opiate with relatively low potency often prescribed for minor pain

psychotherapy that focuses on cognitive processes and problem behaviors
that is sometimes used to treat sleep disorders such as insomnia

theoretical repository of information shared by all people across cultures, as
described by Carl Jung

awareness of internal and external stimuli

device used to treat sleep apnea; includes a mask that fits
over the sleeper’s nose and mouth, which is connected to a pump that pumps air into the person’s
airways, forcing them to remain open

type of low frequency, high amplitude brain wave characteristic of stage 3 and stage 4 sleep

drug that tends to suppress central nervous system activity

feelings of intense elation and pleasure from drug use

discipline that studies how universal patterns of behavior and cognitive
processes have evolved over time as a result of natural selection

one of a class of drugs that results in profound alterations in sensory and perceptual
experiences, often with vivid hallucinations

tendency to maintain a balance, or optimal level, within a biological system

state of extreme self-focus and attention in which minimal attention is given to external stimuli

consistent difficulty in falling or staying asleep for at least three nights a week over a month’s
time

collection of symptoms brought on by travel from one time zone to another that results from the
mismatch between our internal circadian cycles and our environment

very high amplitude pattern of brain activity associated with stage 2 sleep that may occur in
response to environmental stimuli

hidden meaning of a dream, per Sigmund Freud’s view of the function of dreams

people become aware that they are dreaming and can control the dream’s content

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manifest content

meditation

melatonin

meta-analysis

methadone

methadone clinic

methamphetamine

narcolepsy

night terror

non-REM (NREM)

obstructive sleep apnea

opiate/opioid

parinsomnia

physical dependence

pineal gland

psychological dependence

rapid eye movement (REM) sleep

REM sleep behavior disorder (RBD)

restless leg syndrome

rotating shift work

sleep

storyline of events that occur during a dream, per Sigmund Freud’s view of the
function of dreams

clearing the mind in order to achieve a state of relaxed awareness and focus

hormone secreted by the endocrine gland that serves as an important regulator of the sleep-
wake cycle

study that combines the results of several related studies

synthetic opioid that is less euphorogenic than heroin and similar drugs; used to manage
withdrawal symptoms in opiate users

uses methadone to treat withdrawal symptoms in opiate users

type of amphetamine that can be made from pseudoephedrine, an over-the-counter
drug; widely manufactured and abused

sleep disorder in which the sufferer cannot resist falling to sleep at inopportune times

sleep disorder in which the sleeper experiences a sense of panic and may scream or attempt
to escape from the immediate environment

period of sleep outside periods of rapid eye movement (REM) sleep

sleep disorder defined by episodes when breathing stops during sleep as a
result of blockage of the airway

one of a category of drugs that has strong analgesic properties; opiates are produced from
the resin of the opium poppy; includes heroin, morphine, methadone, and codeine

one of a group of sleep disorders characterized by unwanted, disruptive motor activity
and/or experiences during sleep

changes in normal bodily functions that cause a drug user to experience
withdrawal symptoms upon cessation of use

endocrine structure located inside the brain that releases melatonin

emotional, rather than a physical, need for a drug which may be used to
relieve psychological distress

period of sleep characterized by brain waves very similar to those
during wakefulness and by darting movements of the eyes under closed eyelids

sleep disorder in which the muscle paralysis associated with the
REM sleep phase does not occur; sleepers have high levels of physical activity during REM sleep,
especially during disturbing dreams

sleep disorder in which the sufferer has uncomfortable sensations in the legs
when trying to fall asleep that are relieved by moving the legs

work schedule that changes from early to late on a daily or weekly basis

state marked by relatively low levels of physical activity and reduced sensory awareness that is
distinct from periods of rest that occur during wakefulness

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sleep apnea

sleep debt

sleep rebound

sleep regulation

sleep spindle

sleepwalking

stage 1 sleep

stage 2 sleep

stage 3 sleep

stage 4 sleep

stimulant

sudden infant death syndrome (SIDS)

suprachiasmatic nucleus (SCN)

theta wave

tolerance

wakefulness

withdrawal

sleep disorder defined by episodes during which breathing stops during sleep

result of insufficient sleep on a chronic basis

sleep-deprived individuals will experience shorter sleep latencies during subsequent
opportunities for sleep

brain’s control of switching between sleep and wakefulness as well as coordinating this
cycle with the outside world

rapid burst of high frequency brain waves during stage 2 sleep that may be important for
learning and memory

(also, somnambulism) sleep disorder in which the sleeper engages in relatively complex
behaviors

first stage of sleep; transitional phase that occurs between wakefulness and sleep; the
period during which a person drifts off to sleep

second stage of sleep; the body goes into deep relaxation; characterized by the appearance
of sleep spindles

third stage of sleep; deep sleep characterized by low frequency, high amplitude delta waves

fourth stage of sleep; deep sleep characterized by low frequency, high amplitude delta
waves

drug that tends to increase overall levels of neural activity; includes caffeine, nicotine,
amphetamines, and cocaine

infant (one year old or younger) with no apparent medical
condition suddenly dies during sleep

area of the hypothalamus in which the body’s biological clock is located

type of low frequency, high amplitude brain wave characteristic of stage 1 and stage 2 sleep

state of requiring increasing quantities of the drug to gain the desired effect

characterized by high levels of sensory awareness, thought, and behavior

variety of negative symptoms experienced when drug use is discontinued

Summary

4.1 What Is Consciousness?
States of consciousness vary over the course of the day and throughout our lives. Important factors
in these changes are the biological rhythms, and, more specifically, the circadian rhythms generated
by the suprachiasmatic nucleus (SCN). Typically, our biological clocks are aligned with our external
environment, and light tends to be an important cue in setting this clock. When people travel across
multiple time zones or work rotating shifts, they can experience disruptions of their circadian cycles that
can lead to insomnia, sleepiness, and decreased alertness. Bright light therapy has shown to be promising
in dealing with circadian disruptions. If people go extended periods of time without sleep, they will
accrue a sleep debt and potentially experience a number of adverse psychological and physiological
consequences.

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4.2 Sleep and Why We Sleep
We devote a very large portion of time to sleep, and our brains have complex systems that control various
aspects of sleep. Several hormones important for physical growth and maturation are secreted during
sleep. While the reason we sleep remains something of a mystery, there is some evidence to suggest that
sleep is very important to learning and memory.

4.3 Stages of Sleep
The different stages of sleep are characterized by the patterns of brain waves associated with each stage.
As a person transitions from being awake to falling asleep, alpha waves are replaced by theta waves.
Sleep spindles and K-complexes emerge in stage 2 sleep. Stage 3 and stage 4 are described as slow-wave
sleep that is marked by a predominance of delta waves. REM sleep involves rapid movements of the
eyes, paralysis of voluntary muscles, and dreaming. Both NREM and REM sleep appear to play important
roles in learning and memory. Dreams may represent life events that are important to the dreamer.
Alternatively, dreaming may represent a state of protoconsciousness, or a virtual reality, in the mind that
helps a person during consciousness.

4.4 Sleep Problems and Disorders
Many individuals suffer from some type of sleep disorder or disturbance at some point in their lives.
Insomnia is a common experience in which people have difficulty falling or staying asleep. Parasomnias
involve unwanted motor behavior or experiences throughout the sleep cycle and include RBD,
sleepwalking, restless leg syndrome, and night terrors. Sleep apnea occurs when individuals stop
breathing during their sleep, and in the case of sudden infant death syndrome, infants will stop breathing
during sleep and die. Narcolepsy involves an irresistible urge to fall asleep during waking hours and is
often associated with cataplexy and hallucination.

4.5 Substance Use and Abuse
Substance use disorder is defined in DSM-5 as a compulsive pattern of drug use despite negative
consequences. Both physical and psychological dependence are important parts of this disorder. Alcohol,
barbiturates, and benzodiazepines are central nervous system depressants that affect GABA
neurotransmission. Cocaine, amphetamine, cathinones, and MDMA are all central nervous stimulants
that agonize dopamine neurotransmission, while nicotine and caffeine affect acetylcholine and adenosine,
respectively. Opiate drugs serve as powerful analgesics through their effects on the endogenous opioid
neurotransmitter system, and hallucinogenic drugs cause pronounced changes in sensory and perceptual
experiences. The hallucinogens are variable with regards to the specific neurotransmitter systems they
affect.

4.6 Other States of Consciousness
Hypnosis is a focus on the self that involves suggested changes of behavior and experience. Meditation
involves relaxed, yet focused, awareness. Both hypnotic and meditative states may involve altered states of
consciousness that have potential application for the treatment of a variety of physical and psychological
disorders.

Review Questions

1. The body’s biological clock is located in the
________.

a. hippocampus
b. thalamus
c. hypothalamus
d. pituitary gland

2. ________ occurs when there is a chronic
deficiency in sleep.

a. jet lag
b. rotating shift work
c. circadian rhythm
d. sleep debt

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3. ________ cycles occur roughly once every 24
hours.

a. biological
b. circadian
c. rotating
d. conscious

4. ________ is one way in which people can help
reset their biological clocks.

a. Light-dark exposure
b. coffee consumption
c. alcohol consumption
d. napping

5. Growth hormone is secreted by the ________
while we sleep.

a. pineal gland
b. thyroid
c. pituitary gland
d. pancreas

6. The ________ plays a role in controlling slow-
wave sleep.

a. hypothalamus
b. thalamus
c. pons
d. both a and b

7. ________ is a hormone secreted by the pineal
gland that plays a role in regulating biological
rhythms and immune function.

a. growth hormone
b. melatonin
c. LH
d. FSH

8. ________ appears to be especially important for
enhanced performance on recently learned tasks.

a. melatonin
b. slow-wave sleep
c. sleep deprivation
d. growth hormone

9. ________ is(are) described as slow-wave sleep.
a. stage 1
b. stage 2
c. stage 3 and stage 4
d. REM sleep

10. Sleep spindles and K-complexes are most
often associated with ________ sleep.

a. stage 1
b. stage 2
c. stage 3 and stage 4
d. REM

11. Symptoms of ________ may be improved by
REM deprivation.

a. schizophrenia
b. Parkinson’s disease
c. depression
d. generalized anxiety disorder

12. The ________ content of a dream refers to the
true meaning of the dream.

a. latent
b. manifest
c. collective unconscious
d. important

13. ________ is loss of muscle tone or control that
is often associated with narcolepsy.

a. RBD
b. CPAP
c. cataplexy
d. insomnia

14. An individual may suffer from ________ if
there is a disruption in the brain signals that are
sent to the muscles that regulate breathing.

a. central sleep apnea
b. obstructive sleep apnea
c. narcolepsy
d. SIDS

15. The most common treatment for ________
involves the use of amphetamine-like medications.

a. sleep apnea
b. RBD
c. SIDS
d. narcolepsy

16. ________ is another word for sleepwalking.
a. insomnia
b. somnambulism
c. cataplexy
d. narcolepsy

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17. ________ occurs when a drug user requires
more and more of a given drug in order to
experience the same effects of the drug.

a. withdrawal
b. psychological dependence
c. tolerance
d. reuptake

18. Cocaine blocks the reuptake of ________.
a. GABA
b. glutamate
c. acetylcholine
d. dopamine

19. ________ refers to drug craving.
a. psychological dependence
b. antagonism
c. agonism
d. physical dependence

20. LSD affects ________ neurotransmission.
a. dopamine
b. serotonin
c. acetylcholine
d. norepinephrine

21. ________ is most effective in individuals that
are very open to the power of suggestion.

a. hypnosis
b. meditation
c. mindful awareness
d. cognitive therapy

22. ________ has its roots in religious practice.
a. hypnosis
b. meditation
c. cognitive therapy
d. behavioral therapy

23. Meditation may be helpful in ________.
a. pain management
b. stress control
c. treating the flu
d. both a and b

24. Research suggests that cognitive processes,
such as learning, may be affected by ________.

a. hypnosis
b. meditation
c. mindful awareness
d. progressive relaxation

Critical Thinking Questions

25. Healthcare professionals often work rotating shifts. Why is this problematic? What can be done to deal
with potential problems?

26. Generally, humans are considered diurnal which means we are awake during the day and asleep
during the night. Many rodents, on the other hand, are nocturnal. Why do you think different animals
have such different sleep-wake cycles?

27. If theories that assert sleep is necessary for restoration and recovery from daily energetic demands
are correct, what do you predict about the relationship that would exist between individuals’ total sleep
duration and their level of activity?

28. How could researchers determine if given areas of the brain are involved in the regulation of sleep?

29. Differentiate the evolutionary theories of sleep and make a case for the one with the most compelling
evidence.

30. Freud believed that dreams provide important insight into the unconscious mind. He maintained that
a dream’s manifest content could provide clues into an individual’s unconscious. What potential criticisms
exist for this particular perspective?

31. Some people claim that sleepwalking and talking in your sleep involve individuals acting out their
dreams. Why is this particular explanation unlikely?

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32. One of the recommendations that therapists will make to people who suffer from insomnia is to spend
less waking time in bed. Why do you think spending waking time in bed might interfere with the ability
to fall asleep later?

33. How is narcolepsy with cataplexy similar to and different from REM sleep?

34. The negative health consequences of both alcohol and tobacco products are well-documented. A drug
like marijuana, on the other hand, is generally considered to be as safe, if not safer than these legal drugs.
Why do you think marijuana use continues to be illegal in many parts of the United States?

35. Why are programs designed to educate people about the dangers of using tobacco products just as
important as developing tobacco cessation programs?

36. What advantages exist for researching the potential health benefits of hypnosis?

37. What types of studies would be most convincing regarding the effectiveness of meditation in the
treatment for some type of physical or mental disorder?

Personal Application Questions

38. We experience shifts in our circadian clocks in the fall and spring of each year with time changes
associated with daylight saving time. Is springing ahead or falling back easier for you to adjust to, and
why do you think that is?

39. What do you do to adjust to the differences in your daily schedule throughout the week? Are you
running a sleep debt when daylight saving time begins or ends?

40. Have you (or someone you know) ever experienced significant periods of sleep deprivation because of
simple insomnia, high levels of stress, or as a side effect from a medication? What were the consequences
of missing out on sleep?

41. Researchers believe that one important function of sleep is to facilitate learning and memory. How
does knowing this help you in your college studies? What changes could you make to your study and
sleep habits to maximize your mastery of the material covered in class?

42. What factors might contribute to your own experiences with insomnia?

43. Many people experiment with some sort of psychoactive substance at some point in their lives. Why
do you think people are motivated to use substances that alter consciousness?

44. Under what circumstances would you be willing to consider hypnosis and/or meditation as a
treatment option? What kind of information would you need before you made a decision to use these
techniques?

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Chapter 5

Sensation and Perception

Figure 5.1 If you were standing in the midst of this street scene, you would be absorbing and processing numerous
pieces of sensory input. (credit: modification of work by Cory Zanker)

Chapter Outline

5.1 Sensation versus Perception

5.2 Waves and Wavelengths

5.3 Vision

5.4 Hearing

5.5 The Other Senses

5.6 Gestalt Principles of Perception

Introduction

Imagine standing on a city street corner. You might be struck by movement everywhere as cars and people
go about their business, by the sound of a street musician’s melody or a horn honking in the distance,
by the smell of exhaust fumes or of food being sold by a nearby vendor, and by the sensation of hard
pavement under your feet.

We rely on our sensory systems to provide important information about our surroundings. We use this
information to successfully navigate and interact with our environment so that we can find nourishment,
seek shelter, maintain social relationships, and avoid potentially dangerous situations.

This chapter will provide an overview of how sensory information is received and processed by the
nervous system and how that affects our conscious experience of the world. We begin by learning the
distinction between sensation and perception. Then we consider the physical properties of light and sound
stimuli, along with an overview of the basic structure and function of the major sensory systems. The
chapter will close with a discussion of a historically important theory of perception called Gestalt.

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5.1 Sensation versus Perception

Learning Objectives

By the end of this section, you will be able to:
• Distinguish between sensation and perception
• Describe the concepts of absolute threshold and difference threshold
• Discuss the roles attention, motivation, and sensory adaptation play in perception

SENSATION

What does it mean to sense something? Sensory receptors are specialized neurons that respond to specific
types of stimuli. When sensory information is detected by a sensory receptor, sensation has occurred. For
example, light that enters the eye causes chemical changes in cells that line the back of the eye. These
cells relay messages, in the form of action potentials (as you learned when studying biopsychology), to
the central nervous system. The conversion from sensory stimulus energy to action potential is known as
transduction.

You have probably known since elementary school that we have five senses: vision, hearing (audition),
smell (olfaction), taste (gustation), and touch (somatosensation). It turns out that this notion of five
senses is oversimplified. We also have sensory systems that provide information about balance (the
vestibular sense), body position and movement (proprioception and kinesthesia), pain (nociception), and
temperature (thermoception).

The sensitivity of a given sensory system to the relevant stimuli can be expressed as an absolute threshold.
Absolute threshold refers to the minimum amount of stimulus energy that must be present for the
stimulus to be detected 50% of the time. Another way to think about this is by asking how dim can a light
be or how soft can a sound be and still be detected half of the time. The sensitivity of our sensory receptors
can be quite amazing. It has been estimated that on a clear night, the most sensitive sensory cells in the
back of the eye can detect a candle flame 30 miles away (Okawa & Sampath, 2007). Under quiet conditions,
the hair cells (the receptor cells of the inner ear) can detect the tick of a clock 20 feet away (Galanter, 1962).

It is also possible for us to get messages that are presented below the threshold for conscious
awareness—these are called subliminal messages. A stimulus reaches a physiological threshold when it
is strong enough to excite sensory receptors and send nerve impulses to the brain: This is an absolute
threshold. A message below that threshold is said to be subliminal: We receive it, but we are not
consciously aware of it. Over the years there has been a great deal of speculation about the use of
subliminal messages in advertising, rock music, and self-help audio programs. Research evidence shows
that in laboratory settings, people can process and respond to information outside of awareness. But
this does not mean that we obey these messages like zombies; in fact, hidden messages have little effect
on behavior outside the laboratory (Kunst-Wilson & Zajonc, 1980; Rensink, 2004; Nelson, 2008; Radel,
Sarrazin, Legrain, & Gobancé, 2009; Loersch, Durso, & Petty, 2013).

Absolute thresholds are generally measured under incredibly controlled conditions in situations that are
optimal for sensitivity. Sometimes, we are more interested in how much difference in stimuli is required
to detect a difference between them. This is known as the just noticeable difference (jnd) or difference
threshold. Unlike the absolute threshold, the difference threshold changes depending on the stimulus
intensity. As an example, imagine yourself in a very dark movie theater. If an audience member were to
receive a text message that caused the cell phone screen to light up, chances are that many people would
notice the change in illumination in the theater. However, if the same thing happened in a brightly lit
arena during a basketball game, very few people would notice. The cell phone brightness does not change,
but its ability to be detected as a change in illumination varies dramatically between the two contexts.
Ernst Weber proposed this theory of change in difference threshold in the 1830s, and it has become known
as Weber’s law: The difference threshold is a constant fraction of the original stimulus, as the example

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illustrates.

PERCEPTION

While our sensory receptors are constantly collecting information from the environment, it is ultimately
how we interpret that information that affects how we interact with the world. Perception refers to the
way sensory information is organized, interpreted, and consciously experienced. Perception involves both
bottom-up and top-down processing. Bottom-up processing refers to sensory information from a stimulus
in the environment driving a process, and top-down processing refers to knowledge and expectancy
driving a process, as shown in Figure 5.2 (Egeth & Yantis, 1997; Fine & Minnery, 2009; Yantis & Egeth,
1999).

Figure 5.2 Top-down and bottom-up are ways we process our perceptions.

Imagine that you and some friends are sitting in a crowded restaurant eating lunch and talking. It is
very noisy, and you are concentrating on your friend’s face to hear what she is saying, then the sound
of breaking glass and clang of metal pans hitting the floor rings out. The server dropped a large tray of
food. Although you were attending to your meal and conversation, that crashing sound would likely get
through your attentional filters and capture your attention. You would have no choice but to notice it. That
attentional capture would be caused by the sound from the environment: it would be bottom-up.

Alternatively, top-down processes are generally goal directed, slow, deliberate, effortful, and under your
control (Fine & Minnery, 2009; Miller & Cohen, 2001; Miller & D’Esposito, 2005). For instance, if you
misplaced your keys, how would you look for them? If you had a yellow key fob, you would probably look
for yellowness of a certain size in specific locations, such as on the counter, coffee table, and other similar
places. You would not look for yellowness on your ceiling fan, because you know keys are not normally
lying on top of a ceiling fan. That act of searching for a certain size of yellowness in some locations and not
others would be top-down—under your control and based on your experience.

One way to think of this concept is that sensation is a physical process, whereas perception is
psychological. For example, upon walking into a kitchen and smelling the scent of baking cinnamon rolls,
the sensation is the scent receptors detecting the odor of cinnamon, but the perception may be “Mmm, this
smells like the bread Grandma used to bake when the family gathered for holidays.”

Although our perceptions are built from sensations, not all sensations result in perception. In fact, we often
don’t perceive stimuli that remain relatively constant over prolonged periods of time. This is known as
sensory adaptation. Imagine going to a city that you have never visited. You check in to the hotel, but
when you get to your room, there is a road construction sign with a bright flashing light outside your
window. Unfortunately, there are no other rooms available, so you are stuck with a flashing light. You
decide to watch television to unwind. The flashing light was extremely annoying when you first entered
your room. It was as if someone was continually turning a bright yellow spotlight on and off in your
room, but after watching television for a short while, you no longer notice the light flashing. The light
is still flashing and filling your room with yellow light every few seconds, and the photoreceptors in
your eyes still sense the light, but you no longer perceive the rapid changes in lighting conditions. That

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you no longer perceive the flashing light demonstrates sensory adaptation and shows that while closely
associated, sensation and perception are different.

There is another factor that affects sensation and perception: attention. Attention plays a significant role
in determining what is sensed versus what is perceived. Imagine you are at a party full of music, chatter,
and laughter. You get involved in an interesting conversation with a friend, and you tune out all the
background noise. If someone interrupted you to ask what song had just finished playing, you would
probably be unable to answer that question.

See for yourself how inattentional blindness works by checking out this selective attention test
(http://openstax.org/l/blindness) from Simons and Chabris (1999).

One of the most interesting demonstrations of how important attention is in determining our perception of
the environment occurred in a famous study conducted by Daniel Simons and Christopher Chabris (1999).
In this study, participants watched a video of people dressed in black and white passing basketballs.
Participants were asked to count the number of times the team dressed in white passed the ball. During
the video, a person dressed in a black gorilla costume walks among the two teams. You would think that
someone would notice the gorilla, right? Nearly half of the people who watched the video didn’t notice
the gorilla at all, despite the fact that he was clearly visible for nine seconds. Because participants were
so focused on the number of times the team dressed in white was passing the ball, they completely tuned
out other visual information. Inattentional blindness is the failure to notice something that is completely
visible because the person was actively attending to something else and did not pay attention to other
things (Mack & Rock, 1998; Simons & Chabris, 1999).

In a similar experiment, researchers tested inattentional blindness by asking participants to observe
images moving across a computer screen. They were instructed to focus on either white or black objects,
disregarding the other color. When a red cross passed across the screen, about one third of subjects did not
notice it (Figure 5.3) (Most, Simons, Scholl, & Chabris, 2000).

Figure 5.3 Nearly one third of participants in a study did not notice that a red cross passed on the screen because
their attention was focused on the black or white figures. (credit: Cory Zanker)

Motivation can also affect perception. Have you ever been expecting a really important phone call and,
while taking a shower, you think you hear the phone ringing, only to discover that it is not? If so, then
you have experienced how motivation to detect a meaningful stimulus can shift our ability to discriminate
between a true sensory stimulus and background noise. The ability to identify a stimulus when it is
embedded in a distracting background is called signal detection theory. This might also explain why a

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mother is awakened by a quiet murmur from her baby but not by other sounds that occur while she is
asleep. Signal detection theory has practical applications, such as increasing air traffic controller accuracy.
Controllers need to be able to detect planes among many signals (blips) that appear on the radar screen
and follow those planes as they move through the sky. In fact, the original work of the researcher who
developed signal detection theory was focused on improving the sensitivity of air traffic controllers to
plane blips (Swets, 1964).

Our perceptions can also be affected by our beliefs, values, prejudices, expectations, and life experiences.
As you will see later in this chapter, individuals who are deprived of the experience of binocular vision
during critical periods of development have trouble perceiving depth (Fawcett, Wang, & Birch, 2005). The
shared experiences of people within a given cultural context can have pronounced effects on perception.
For example, Marshall Segall, Donald Campbell, and Melville Herskovits (1963) published the results of a
multinational study in which they demonstrated that individuals from Western cultures were more prone
to experience certain types of visual illusions than individuals from non-Western cultures, and vice versa.
One such illusion that Westerners were more likely to experience was the Müller-Lyer illusion (Figure
5.4): The lines appear to be different lengths, but they are actually the same length.

Figure 5.4 In the Müller-Lyer illusion, lines appear to be different lengths although they are identical. (a) Arrows at
the ends of lines may make the line on the right appear longer, although the lines are the same length. (b) When
applied to a three-dimensional image, the line on the right again may appear longer although both black lines are the
same length.

These perceptual differences were consistent with differences in the types of environmental features
experienced on a regular basis by people in a given cultural context. People in Western cultures, for
example, have a perceptual context of buildings with straight lines, what Segall’s study called a
carpentered world (Segall et al., 1966). In contrast, people from certain non-Western cultures with an
uncarpentered view, such as the Zulu of South Africa, whose villages are made up of round huts arranged
in circles, are less susceptible to this illusion (Segall et al., 1999). It is not just vision that is affected
by cultural factors. Indeed, research has demonstrated that the ability to identify an odor, and rate its
pleasantness and its intensity, varies cross-culturally (Ayabe-Kanamura, Saito, Distel, Martínez-Gómez, &
Hudson, 1998).

Children described as thrill seekers are more likely to show taste preferences for intense sour flavors (Liem,
Westerbeek, Wolterink, Kok, & de Graaf, 2004), which suggests that basic aspects of personality might
affect perception. Furthermore, individuals who hold positive attitudes toward reduced-fat foods are more
likely to rate foods labeled as reduced fat as tasting better than people who have less positive attitudes
about these products (Aaron, Mela, & Evans, 1994).

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5.2 Waves and Wavelengths

Learning Objectives

By the end of this section, you will be able to:
• Describe important physical features of wave forms
• Show how physical properties of light waves are associated with perceptual experience
• Show how physical properties of sound waves are associated with perceptual experience

Visual and auditory stimuli both occur in the form of waves. Although the two stimuli are very different in
terms of composition, wave forms share similar characteristics that are especially important to our visual
and auditory perceptions. In this section, we describe the physical properties of the waves as well as the
perceptual experiences associated with them.

AMPLITUDE AND WAVELENGTH

Two physical characteristics of a wave are amplitude and wavelength (Figure 5.5). The amplitude of a
wave is the distance from the center line to the top point of the crest or the bottom point of the trough.
Wavelength refers to the length of a wave from one peak to the next.

Figure 5.5 The amplitude or height of a wave is measured from the peak to the trough. The wavelength is measured
from peak to peak.

Wavelength is directly related to the frequency of a given wave form. Frequency refers to the number of
waves that pass a given point in a given time period and is often expressed in terms of hertz (Hz), or cycles
per second. Longer wavelengths will have lower frequencies, and shorter wavelengths will have higher
frequencies (Figure 5.6).

Figure 5.6 This figure illustrates waves of differing wavelengths/frequencies. At the top of the figure, the red wave
has a long wavelength/short frequency. Moving from top to bottom, the wavelengths decrease and frequencies
increase.

LIGHT WAVES

The visible spectrum is the portion of the larger electromagnetic spectrum that we can see. As Figure 5.7
shows, the electromagnetic spectrum encompasses all of the electromagnetic radiation that occurs in our

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environment and includes gamma rays, x-rays, ultraviolet light, visible light, infrared light, microwaves,
and radio waves. The visible spectrum in humans is associated with wavelengths that range from 380 to
740 nm—a very small distance, since a nanometer (nm) is one billionth of a meter. Other species can detect
other portions of the electromagnetic spectrum. For instance, honeybees can see light in the ultraviolet
range (Wakakuwa, Stavenga, & Arikawa, 2007), and some snakes can detect infrared radiation in addition
to more traditional visual light cues (Chen, Deng, Brauth, Ding, & Tang, 2012; Hartline, Kass, & Loop,
1978).

Figure 5.7 Light that is visible to humans makes up only a small portion of the electromagnetic spectrum.

In humans, light wavelength is associated with perception of color (Figure 5.8). Within the visible
spectrum, our experience of red is associated with longer wavelengths, greens are intermediate, and blues
and violets are shorter in wavelength. (An easy way to remember this is the mnemonic ROYGBIV: red,
orange, yellow, green, blue, indigo, violet.) The amplitude of light waves is associated with our experience
of brightness or intensity of color, with larger amplitudes appearing brighter.

Figure 5.8 Different wavelengths of light are associated with our perception of different colors. (credit: modification
of work by Johannes Ahlmann)

SOUND WAVES

Like light waves, the physical properties of sound waves are associated with various aspects of our
perception of sound. The frequency of a sound wave is associated with our perception of that sound’s
pitch. High-frequency sound waves are perceived as high-pitched sounds, while low-frequency sound
waves are perceived as low-pitched sounds. The audible range of sound frequencies is between 20 and
20000 Hz, with greatest sensitivity to those frequencies that fall in the middle of this range.

As was the case with the visible spectrum, other species show differences in their audible ranges. For
instance, chickens have a very limited audible range, from 125 to 2000 Hz. Mice have an audible range
from 1000 to 91000 Hz, and the beluga whale’s audible range is from 1000 to 123000 Hz. Our pet dogs and

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cats have audible ranges of about 70–45000 Hz and 45–64000 Hz, respectively (Strain, 2003).

The loudness of a given sound is closely associated with the amplitude of the sound wave. Higher
amplitudes are associated with louder sounds. Loudness is measured in terms of decibels (dB), a
logarithmic unit of sound intensity. A typical conversation would correlate with 60 dB; a rock concert
might check in at 120 dB (Figure 5.9). A whisper 5 feet away or rustling leaves are at the low end of
our hearing range; sounds like a window air conditioner, a normal conversation, and even heavy traffic
or a vacuum cleaner are within a tolerable range. However, there is the potential for hearing damage
from about 80 dB to 130 dB: These are sounds of a food processor, power lawnmower, heavy truck
(25 feet away), subway train (20 feet away), live rock music, and a jackhammer. About one-third of all
hearing loss is due to noise exposure, and the louder the sound, the shorter the exposure needed to
cause hearing damage (Le, Straatman, Lea, & Westerberg, 2017). Listening to music through earbuds at
maximum volume (around 100–105 decibels) can cause noise-induced hearing loss after 15 minutes of
exposure. Although listening to music at maximum volume may not seem to cause damage, it increases
the risk of age-related hearing loss (Kujawa & Liberman, 2006). The threshold for pain is about 130 dB, a
jet plane taking off or a revolver firing at close range (Dunkle, 1982).

Figure 5.9 This figure illustrates the loudness of common sounds. (credit “planes”: modification of work by Max
Pfandl; credit “crowd”: modification of work by Christian Holmér; credit: “earbuds”: modification of work by “Skinny
Guy Lover_Flickr”/Flickr; credit “traffic”: modification of work by “quinntheislander_Pixabay”/Pixabay; credit “talking”:
modification of work by Joi Ito; credit “leaves”: modification of work by Aurelijus Valeiša)

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Although wave amplitude is generally associated with loudness, there is some interaction between
frequency and amplitude in our perception of loudness within the audible range. For example, a 10 Hz
sound wave is inaudible no matter the amplitude of the wave. A 1000 Hz sound wave, on the other hand,
would vary dramatically in terms of perceived loudness as the amplitude of the wave increased.

Watch this brief video about our perception of frequency and amplitude (http://openstax.org/l/
frequency) to learn more.

Of course, different musical instruments can play the same musical note at the same level of loudness, yet
they still sound quite different. This is known as the timbre of a sound. Timbre refers to a sound’s purity,
and it is affected by the complex interplay of frequency, amplitude, and timing of sound waves.

5.3 Vision

Learning Objectives

By the end of this section, you will be able to:
• Describe the basic anatomy of the visual system
• Discuss how rods and cones contribute to different aspects of vision
• Describe how monocular and binocular cues are used in the perception of depth

The visual system constructs a mental representation of the world around us (Figure 5.10). This
contributes to our ability to successfully navigate through physical space and interact with important
individuals and objects in our environments. This section will provide an overview of the basic anatomy
and function of the visual system. In addition, we will explore our ability to perceive color and depth.

Figure 5.10 Our eyes take in sensory information that helps us understand the world around us. (credit “top left”:
modification of work by “rajkumar1220″/Flickr”; credit “top right”: modification of work by Thomas Leuthard; credit
“middle left”: modification of work by Demietrich Baker; credit “middle right”: modification of work by
“kaybee07″/Flickr; credit “bottom left”: modification of work by “Isengardt”/Flickr; credit “bottom right”: modification of
work by Willem Heerbaart)

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ANATOMY OF THE VISUAL SYSTEM

The eye is the major sensory organ involved in vision (Figure 5.11). Light waves are transmitted across the
cornea and enter the eye through the pupil. The cornea is the transparent covering over the eye. It serves
as a barrier between the inner eye and the outside world, and it is involved in focusing light waves that
enter the eye. The pupil is the small opening in the eye through which light passes, and the size of the
pupil can change as a function of light levels as well as emotional arousal. When light levels are low, the
pupil will become dilated, or expanded, to allow more light to enter the eye. When light levels are high,
the pupil will constrict, or become smaller, to reduce the amount of light that enters the eye. The pupil’s
size is controlled by muscles that are connected to the iris, which is the colored portion of the eye.

Figure 5.11 The anatomy of the eye is illustrated in this diagram.

After passing through the pupil, light crosses the lens, a curved, transparent structure that serves to
provide additional focus. The lens is attached to muscles that can change its shape to aid in focusing
light that is reflected from near or far objects. In a normal-sighted individual, the lens will focus images
perfectly on a small indentation in the back of the eye known as the fovea, which is part of the retina, the
light-sensitive lining of the eye. The fovea contains densely packed specialized photoreceptor cells (Figure
5.12). These photoreceptor cells, known as cones, are light-detecting cells. The cones are specialized types
of photoreceptors that work best in bright light conditions. Cones are very sensitive to acute detail and
provide tremendous spatial resolution. They also are directly involved in our ability to perceive color.

While cones are concentrated in the fovea, where images tend to be focused, rods, another type of
photoreceptor, are located throughout the remainder of the retina. Rods are specialized photoreceptors
that work well in low light conditions, and while they lack the spatial resolution and color function of the
cones, they are involved in our vision in dimly lit environments as well as in our perception of movement
on the periphery of our visual field.

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Figure 5.12 The two types of photoreceptors are shown in this image. Cones are colored green and rods are blue.

We have all experienced the different sensitivities of rods and cones when making the transition from
a brightly lit environment to a dimly lit environment. Imagine going to see a blockbuster movie on a
clear summer day. As you walk from the brightly lit lobby into the dark theater, you notice that you
immediately have difficulty seeing much of anything. After a few minutes, you begin to adjust to the
darkness and can see the interior of the theater. In the bright environment, your vision was dominated
primarily by cone activity. As you move to the dark environment, rod activity dominates, but there is a
delay in transitioning between the phases. If your rods do not transform light into nerve impulses as easily
and efficiently as they should, you will have difficulty seeing in dim light, a condition known as night
blindness.

Rods and cones are connected (via several interneurons) to retinal ganglion cells. Axons from the retinal
ganglion cells converge and exit through the back of the eye to form the optic nerve. The optic nerve carries
visual information from the retina to the brain. There is a point in the visual field called the blind spot:
Even when light from a small object is focused on the blind spot, we do not see it. We are not consciously
aware of our blind spots for two reasons: First, each eye gets a slightly different view of the visual field;
therefore, the blind spots do not overlap. Second, our visual system fills in the blind spot so that although
we cannot respond to visual information that occurs in that portion of the visual field, we are also not
aware that information is missing.

The optic nerve from each eye merges just below the brain at a point called the optic chiasm. As Figure
5.13 shows, the optic chiasm is an X-shaped structure that sits just below the cerebral cortex at the front of
the brain. At the point of the optic chiasm, information from the right visual field (which comes from both
eyes) is sent to the left side of the brain, and information from the left visual field is sent to the right side
of the brain.

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Figure 5.13 This illustration shows the optic chiasm at the front of the brain and the pathways to the occipital lobe at
the back of the brain, where visual sensations are processed into meaningful perceptions.

Once inside the brain, visual information is sent via a number of structures to the occipital lobe at the
back of the brain for processing. Visual information might be processed in parallel pathways which can
generally be described as the “what pathway” and the “where/how” pathway. The “what pathway”
is involved in object recognition and identification, while the “where/how pathway” is involved with
location in space and how one might interact with a particular visual stimulus (Milner & Goodale, 2008;
Ungerleider & Haxby, 1994). For example, when you see a ball rolling down the street, the “what pathway”
identifies what the object is, and the “where/how pathway” identifies its location or movement in space.

The Ethics of Research Using Animals

David Hubel and Torsten Wiesel were awarded the Nobel Prize in Medicine in 1981 for their research on
the visual system. They collaborated for more than twenty years and made significant discoveries about the
neurology of visual perception (Hubel & Wiesel, 1959, 1962, 1963, 1970; Wiesel & Hubel, 1963). They studied
animals, mostly cats and monkeys. Although they used several techniques, they did considerable single unit
recordings, during which tiny electrodes were inserted in the animal’s brain to determine when a single cell
was activated. Among their many discoveries, they found that specific brain cells respond to lines with specific
orientations (called ocular dominance), and they mapped the way those cells are arranged in areas of the
visual cortex known as columns and hypercolumns.

In some of their research, they sutured one eye of newborn kittens closed and followed the development of the
kittens’ vision. They discovered there was a critical period of development for vision. If kittens were deprived
of input from one eye, other areas of their visual cortex filled in the area that was normally used by the eye
that was sewn closed. In other words, neural connections that exist at birth can be lost if they are deprived of
sensory input.

What do you think about sewing a kitten’s eye closed for research? To many animal advocates, this would
seem brutal, abusive, and unethical. What if you could do research that would help ensure babies and children
born with certain conditions could develop normal vision instead of becoming blind? Would you want that
research done? Would you conduct that research, even if it meant causing some harm to cats? Would you
think the same way if you were the parent of such a child? What if you worked at the animal shelter?

WHAT DO YOU THINK?

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Like virtually every other industrialized nation, the United States permits medical experimentation on animals,
with few limitations (assuming sufficient scientific justification). The goal of any laws that exist is not to ban
such tests but rather to limit unnecessary animal suffering by establishing standards for the humane treatment
and housing of animals in laboratories.

As explained by Stephen Latham, the director of the Interdisciplinary Center for Bioethics at Yale (2012),
possible legal and regulatory approaches to animal testing vary on a continuum from strong government
regulation and monitoring of all experimentation at one end, to a self-regulated approach that depends on the
ethics of the researchers at the other end. The United Kingdom has the most significant regulatory scheme,
whereas Japan uses the self-regulation approach. The U.S. approach is somewhere in the middle, the result
of a gradual blending of the two approaches.

There is no question that medical research is a valuable and important practice. The question is whether the
use of animals is a necessary or even best practice for producing the most reliable results. Alternatives include
the use of patient-drug databases, virtual drug trials, computer models and simulations, and noninvasive
imaging techniques such as magnetic resonance imaging and computed tomography scans (“Animals in
Science/Alternatives,” n.d.). Other techniques, such as microdosing, use humans not as test animals but as a
means to improve the accuracy and reliability of test results. In vitro methods based on human cell and tissue
cultures, stem cells, and genetic testing methods are also increasingly available.

Today, at the local level, any facility that uses animals and receives federal funding must have an Institutional
Animal Care and Use Committee (IACUC) that ensures that the NIH guidelines are being followed. The IACUC
must include researchers, administrators, a veterinarian, and at least one person with no ties to the institution:
that is, a concerned citizen. This committee also performs inspections of laboratories and protocols.

COLOR AND DEPTH PERCEPTION

We do not see the world in black and white; neither do we see it as two-dimensional (2-D) or flat (just
height and width, no depth). Let’s look at how color vision works and how we perceive three dimensions
(height, width, and depth).

Color Vision

Normal-sighted individuals have three different types of cones that mediate color vision. Each of these
cone types is maximally sensitive to a slightly different wavelength of light. According to the trichromatic
theory of color vision, shown in Figure 5.14, all colors in the spectrum can be produced by combining
red, green, and blue. The three types of cones are each receptive to one of the colors.

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Figure 5.14 This figure illustrates the different sensitivities for the three cone types found in a normal-sighted
individual. (credit: modification of work by Vanessa Ezekowitz)

CONNECT THE CONCEPTS
CONNECT THE CONCEPTS

Colorblindness: A Personal Story

Several years ago, I dressed to go to a public function and walked into the kitchen where my 7-year-old daughter
sat. She looked up at me, and in her most stern voice, said, “You can’t wear that.” I asked, “Why not?” and she
informed me the colors of my clothes did not match. She had complained frequently that I was bad at matching
my shirts, pants, and ties, but this time, she sounded especially alarmed. As a single father with no one else to
ask at home, I drove us to the nearest convenience store and asked the store clerk if my clothes matched. She
said my pants were a bright green color, my shirt was a reddish orange, and my tie was brown. She looked at
my quizzically and said, “No way do your clothes match.” Over the next few days, I started asking my coworkers
and friends if my clothes matched. After several days of being told that my coworkers just thought I had “a really
unique style,” I made an appointment with an eye doctor and was tested (Figure 5.15). It was then that I found
out that I was colorblind. I cannot differentiate between most greens, browns, and reds. Fortunately, other than
unknowingly being badly dressed, my colorblindness rarely harms my day-to-day life.

Figure 5.15 The Ishihara test evaluates color perception by assessing whether individuals can discern
numbers that appear in a circle of dots of varying colors and sizes.

Some forms of color deficiency are rare. Seeing in grayscale (only shades of black and white) is extremely
rare, and people who do so only have rods, which means they have very low visual acuity and cannot see very
well. The most common X-linked inherited abnormality is red-green color blindness (Birch, 2012). Approximately
8% of males with European Caucasian decent, 5% of Asian males, 4% of African males, and less than 2% of

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indigenous American males, Australian males, and Polynesian males have red-green color deficiency (Birch,
2012). Comparatively, only about 0.4% in females from European Caucasian descent have red-green color
deficiency (Birch, 2012).

The trichromatic theory of color vision is not the only theory—another major theory of color vision is
known as the opponent-process theory. According to this theory, color is coded in opponent pairs: black-
white, yellow-blue, and green-red. The basic idea is that some cells of the visual system are excited
by one of the opponent colors and inhibited by the other. So, a cell that was excited by wavelengths
associated with green would be inhibited by wavelengths associated with red, and vice versa. One of
the implications of opponent processing is that we do not experience greenish-reds or yellowish-blues
as colors. Another implication is that this leads to the experience of negative afterimages. An afterimage
describes the continuation of a visual sensation after removal of the stimulus. For example, when you stare
briefly at the sun and then look away from it, you may still perceive a spot of light although the stimulus
(the sun) has been removed. When color is involved in the stimulus, the color pairings identified in the
opponent-process theory lead to a negative afterimage. You can test this concept using the flag in Figure
5.16.

Figure 5.16 Stare at the white dot for 30–60 seconds and then move your eyes to a blank piece of white paper.
What do you see? This is known as a negative afterimage, and it provides empirical support for the opponent-process
theory of color vision.

But these two theories—the trichromatic theory of color vision and the opponent-process theory—are not
mutually exclusive. Research has shown that they just apply to different levels of the nervous system. For
visual processing on the retina, trichromatic theory applies: the cones are responsive to three different
wavelengths that represent red, blue, and green. But once the signal moves past the retina on its way to
the brain, the cells respond in a way consistent with opponent-process theory (Land, 1959; Kaiser, 1997).

Watch this video about color perception (http://openstax.org/l/colorvision) to learn more.

Depth Perception

Our ability to perceive spatial relationships in three-dimensional (3-D) space is known as depth
perception. With depth perception, we can describe things as being in front, behind, above, below, or to

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the side of other things.

Our world is three-dimensional, so it makes sense that our mental representation of the world has three-
dimensional properties. We use a variety of cues in a visual scene to establish our sense of depth. Some of
these are binocular cues, which means that they rely on the use of both eyes. One example of a binocular
depth cue is binocular disparity, the slightly different view of the world that each of our eyes receives. To
experience this slightly different view, do this simple exercise: extend your arm fully and extend one of
your fingers and focus on that finger. Now, close your left eye without moving your head, then open your
left eye and close your right eye without moving your head. You will notice that your finger seems to shift
as you alternate between the two eyes because of the slightly different view each eye has of your finger.

A 3-D movie works on the same principle: the special glasses you wear allow the two slightly different
images projected onto the screen to be seen separately by your left and your right eye. As your brain
processes these images, you have the illusion that the leaping animal or running person is coming right
toward you.

Although we rely on binocular cues to experience depth in our 3-D world, we can also perceive depth in
2-D arrays. Think about all the paintings and photographs you have seen. Generally, you pick up on depth
in these images even though the visual stimulus is 2-D. When we do this, we are relying on a number of
monocular cues, or cues that require only one eye. If you think you can’t see depth with one eye, note
that you don’t bump into things when using only one eye while walking—and, in fact, we have more
monocular cues than binocular cues.

An example of a monocular cue would be what is known as linear perspective. Linear perspective refers to
the fact that we perceive depth when we see two parallel lines that seem to converge in an image (Figure
5.17). Some other monocular depth cues are interposition, the partial overlap of objects, and the relative
size and closeness of images to the horizon.

Figure 5.17 We perceive depth in a two-dimensional figure like this one through the use of monocular cues like
linear perspective, like the parallel lines converging as the road narrows in the distance. (credit: Marc Dalmulder)

Stereoblindness

Bruce Bridgeman was born with an extreme case of lazy eye that resulted in him being stereoblind, or unable
to respond to binocular cues of depth. He relied heavily on monocular depth cues, but he never had a true

DIG DEEPER

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appreciation of the 3-D nature of the world around him. This all changed one night in 2012 while Bruce was
seeing a movie with his wife.

The movie the couple was going to see was shot in 3-D, and even though he thought it was a waste of money,
Bruce paid for the 3-D glasses when he purchased his ticket. As soon as the film began, Bruce put on the
glasses and experienced something completely new. For the first time in his life he appreciated the true depth
of the world around him. Remarkably, his ability to perceive depth persisted outside of the movie theater.

There are cells in the nervous system that respond to binocular depth cues. Normally, these cells require
activation during early development in order to persist, so experts familiar with Bruce’s case (and others like
his) assume that at some point in his development, Bruce must have experienced at least a fleeting moment of
binocular vision. It was enough to ensure the survival of the cells in the visual system tuned to binocular cues.
The mystery now is why it took Bruce nearly 70 years to have these cells activated (Peck, 2012).

5.4 Hearing

Learning Objectives

By the end of this section, you will be able to:
• Describe the basic anatomy and function of the auditory system
• Explain how we encode and perceive pitch
• Discuss how we localize sound

Our auditory system converts pressure waves into meaningful sounds. This translates into our ability
to hear the sounds of nature, to appreciate the beauty of music, and to communicate with one another
through spoken language. This section will provide an overview of the basic anatomy and function of the
auditory system. It will include a discussion of how the sensory stimulus is translated into neural impulses,
where in the brain that information is processed, how we perceive pitch, and how we know where sound
is coming from.

ANATOMY OF THE AUDITORY SYSTEM

The ear can be separated into multiple sections. The outer ear includes the pinna, which is the visible
part of the ear that protrudes from our heads, the auditory canal, and the tympanic membrane, or
eardrum. The middle ear contains three tiny bones known as the ossicles, which are named the malleus
(or hammer), incus (or anvil), and the stapes (or stirrup). The inner ear contains the semi-circular canals,
which are involved in balance and movement (the vestibular sense), and the cochlea. The cochlea is a fluid-
filled, snail-shaped structure that contains the sensory receptor cells (hair cells) of the auditory system
(Figure 5.18).

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Figure 5.18 The ear is divided into outer (pinna and tympanic membrane), middle (the three ossicles: malleus,
incus, and stapes), and inner (cochlea and basilar membrane) divisions.

Sound waves travel along the auditory canal and strike the tympanic membrane, causing it to vibrate. This
vibration results in movement of the three ossicles. As the ossicles move, the stapes presses into a thin
membrane of the cochlea known as the oval window. As the stapes presses into the oval window, the fluid
inside the cochlea begins to move, which in turn stimulates hair cells, which are auditory receptor cells of
the inner ear embedded in the basilar membrane. The basilar membrane is a thin strip of tissue within the
cochlea.

The activation of hair cells is a mechanical process: the stimulation of the hair cell ultimately leads to
activation of the cell. As hair cells become activated, they generate neural impulses that travel along
the auditory nerve to the brain. Auditory information is shuttled to the inferior colliculus, the medial
geniculate nucleus of the thalamus, and finally to the auditory cortex in the temporal lobe of the brain
for processing. Like the visual system, there is also evidence suggesting that information about auditory
recognition and localization is processed in parallel streams (Rauschecker & Tian, 2000; Renier et al., 2009).

PITCH PERCEPTION

Different frequencies of sound waves are associated with differences in our perception of the pitch of those
sounds. Low-frequency sounds are lower pitched, and high-frequency sounds are higher pitched. How
does the auditory system differentiate among various pitches?

Several theories have been proposed to account for pitch perception. We’ll discuss two of them here:
temporal theory and place theory. The temporal theory of pitch perception asserts that frequency is coded
by the activity level of a sensory neuron. This would mean that a given hair cell would fire action potentials
related to the frequency of the sound wave. While this is a very intuitive explanation, we detect such a
broad range of frequencies (20–20,000 Hz) that the frequency of action potentials fired by hair cells cannot
account for the entire range. Because of properties related to sodium channels on the neuronal membrane
that are involved in action potentials, there is a point at which a cell cannot fire any faster (Shamma, 2001).

The place theory of pitch perception suggests that different portions of the basilar membrane are sensitive
to sounds of different frequencies. More specifically, the base of the basilar membrane responds best to
high frequencies and the tip of the basilar membrane responds best to low frequencies. Therefore, hair
cells that are in the base portion would be labeled as high-pitch receptors, while those in the tip of basilar
membrane would be labeled as low-pitch receptors (Shamma, 2001).

In reality, both theories explain different aspects of pitch perception. At frequencies up to about 4000 Hz,
it is clear that both the rate of action potentials and place contribute to our perception of pitch. However,

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much higher frequency sounds can only be encoded using place cues (Shamma, 2001).

SOUND LOCALIZATION

The ability to locate sound in our environments is an important part of hearing. Localizing sound could be
considered similar to the way that we perceive depth in our visual fields. Like the monocular and binocular
cues that provided information about depth, the auditory system uses both monaural (one-eared) and
binaural (two-eared) cues to localize sound.

Each pinna interacts with incoming sound waves differently, depending on the sound’s source relative to
our bodies. This interaction provides a monaural cue that is helpful in locating sounds that occur above or
below and in front or behind us. The sound waves received by your two ears from sounds that come from
directly above, below, in front, or behind you would be identical; therefore, monaural cues are essential
(Grothe, Pecka, & McAlpine, 2010).

Binaural cues, on the other hand, provide information on the location of a sound along a horizontal axis
by relying on differences in patterns of vibration of the eardrum between our two ears. If a sound comes
from an off-center location, it creates two types of binaural cues: interaural level differences and interaural
timing differences. Interaural level difference refers to the fact that a sound coming from the right side of
your body is more intense at your right ear than at your left ear because of the attenuation of the sound
wave as it passes through your head. Interaural timing difference refers to the small difference in the
time at which a given sound wave arrives at each ear (Figure 5.19). Certain brain areas monitor these
differences to construct where along a horizontal axis a sound originates (Grothe et al., 2010).

Figure 5.19 Localizing sound involves the use of both monaural and binaural cues. (credit “plane”: modification of
work by Max Pfandl)

HEARING LOSS

Deafness is the partial or complete inability to hear. Some people are born without hearing, which is
known as congenital deafness. Other people suffer from conductive hearing loss, which is due to a
problem delivering sound energy to the cochlea. Causes for conductive hearing loss include blockage
of the ear canal, a hole in the tympanic membrane, problems with the ossicles, or fluid in the space
between the eardrum and cochlea. Another group of people suffer from sensorineural hearing loss, which

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is the most common form of hearing loss. Sensorineural hearing loss can be caused by many factors,
such as aging, head or acoustic trauma, infections and diseases (such as measles or mumps), medications,
environmental effects such as noise exposure (noise-induced hearing loss, as shown in Figure 5.20),
tumors, and toxins (such as those found in certain solvents and metals).

Figure 5.20 Environmental factors that can lead to sensorineural hearing loss include regular exposure to loud
music or construction equipment. (a) Musical performers and (b) construction workers are at risk for this type of
hearing loss. (credit a: modification of work by “GillyBerlin_Flickr”/Flickr; credit b: modification of work by Nick Allen)

Given the mechanical nature by which the sound wave stimulus is transmitted from the eardrum through
the ossicles to the oval window of the cochlea, some degree of hearing loss is inevitable. With conductive
hearing loss, hearing problems are associated with a failure in the vibration of the eardrum and/or
movement of the ossicles. These problems are often dealt with through devices like hearing aids that
amplify incoming sound waves to make vibration of the eardrum and movement of the ossicles more likely
to occur.

When the hearing problem is associated with a failure to transmit neural signals from the cochlea to the
brain, it is called sensorineural hearing loss. One disease that results in sensorineural hearing loss is
Ménière’s disease. Although not well understood, Ménière’s disease results in a degeneration of inner ear
structures that can lead to hearing loss, tinnitus (constant ringing or buzzing), vertigo (a sense of spinning),
and an increase in pressure within the inner ear (Semaan & Megerian, 2011). This kind of loss cannot be
treated with hearing aids, but some individuals might be candidates for a cochlear implant as a treatment
option. Cochlear implants are electronic devices that consist of a microphone, a speech processor, and
an electrode array. The device receives incoming sound information and directly stimulates the auditory
nerve to transmit information to the brain.

Watch this video about cochlear implant surgeries (http://openstax.org/l/cochlear) to learn more.

Deaf Culture

In the United States and other places around the world, deaf people have their own language, schools, and

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WHAT DO YOU THINK?

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customs. This is called deaf culture. In the United States, deaf individuals often communicate using American
Sign Language (ASL); ASL has no verbal component and is based entirely on visual signs and gestures. The
primary mode of communication is signing. One of the values of deaf culture is to continue traditions like using
sign language rather than teaching deaf children to try to speak, read lips, or have cochlear implant surgery.

When a child is diagnosed as deaf, parents have difficult decisions to make. Should the child be enrolled in
mainstream schools and taught to verbalize and read lips? Or should the child be sent to a school for deaf
children to learn ASL and have significant exposure to deaf culture? Do you think there might be differences in
the way that parents approach these decisions depending on whether or not they are also deaf?

5.5 The Other Senses

Learning Objectives

By the end of this section, you will be able to:
• Describe the basic functions of the chemical senses
• Explain the basic functions of the somatosensory, nociceptive, and thermoceptive sensory

systems
• Describe the basic functions of the vestibular, proprioceptive, and kinesthetic sensory

systems

Vision and hearing have received an incredible amount of attention from researchers over the years.
While there is still much to be learned about how these sensory systems work, we have a much better
understanding of them than of our other sensory modalities. In this section, we will explore our chemical
senses (taste and smell) and our body senses (touch, temperature, pain, balance, and body position).

THE CHEMICAL SENSES

Taste (gustation) and smell (olfaction) are called chemical senses because both have sensory receptors that
respond to molecules in the food we eat or in the air we breathe. There is a pronounced interaction between
our chemical senses. For example, when we describe the flavor of a given food, we are really referring to
both gustatory and olfactory properties of the food working in combination.

Taste (Gustation)

You have learned since elementary school that there are four basic groupings of taste: sweet, salty, sour,
and bitter. Research demonstrates, however, that we have at least six taste groupings. Umami is our fifth
taste. Umami is actually a Japanese word that roughly translates to yummy, and it is associated with
a taste for monosodium glutamate (Kinnamon & Vandenbeuch, 2009). There is also a growing body of
experimental evidence suggesting that we possess a taste for the fatty content of a given food (Mizushige,
Inoue, & Fushiki, 2007).

Molecules from the food and beverages we consume dissolve in our saliva and interact with taste receptors
on our tongue and in our mouth and throat. Taste buds are formed by groupings of taste receptor cells
with hair-like extensions that protrude into the central pore of the taste bud (Figure 5.21). Taste buds
have a life cycle of ten days to two weeks, so even destroying some by burning your tongue won’t have
any long-term effect; they just grow right back. Taste molecules bind to receptors on this extension and
cause chemical changes within the sensory cell that result in neural impulses being transmitted to the brain
via different nerves, depending on where the receptor is located. Taste information is transmitted to the
medulla, thalamus, and limbic system, and to the gustatory cortex, which is tucked underneath the overlap

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between the frontal and temporal lobes (Maffei, Haley, & Fontanini, 2012; Roper, 2013).

Figure 5.21 (a) Taste buds are composed of a number of individual taste receptors cells that transmit information to
nerves. (b) This micrograph shows a close-up view of the tongue’s surface. (credit a: modification of work by Jonas
Töle; credit b: scale-bar data from Matt Russell)

Smell (Olfaction)

Olfactory receptor cells are located in a mucous membrane at the top of the nose. Small hair-like
extensions from these receptors serve as the sites for odor molecules dissolved in the mucus to interact
with chemical receptors located on these extensions (Figure 5.22). Once an odor molecule has bound a
given receptor, chemical changes within the cell result in signals being sent to the olfactory bulb: a bulb-
like structure at the tip of the frontal lobe where the olfactory nerves begin. From the olfactory bulb,
information is sent to regions of the limbic system and to the primary olfactory cortex, which is located
very near the gustatory cortex (Lodovichi & Belluscio, 2012; Spors et al., 2013).

Figure 5.22 Olfactory receptors are the hair-like parts that extend from the olfactory bulb into the mucous membrane
of the nasal cavity.

There is tremendous variation in the sensitivity of the olfactory systems of different species. We often think
of dogs as having far superior olfactory systems than our own, and indeed, dogs can do some remarkable
things with their noses. There is some evidence to suggest that dogs can “smell” dangerous drops in blood

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glucose levels as well as cancerous tumors (Wells, 2010). Dogs’ extraordinary olfactory abilities may be
due to the increased number of functional genes for olfactory receptors (between 800 and 1200), compared
to the fewer than 400 observed in humans and other primates (Niimura & Nei, 2007).

Many species respond to chemical messages, known as pheromones, sent by another individual (Wysocki
& Preti, 2004). Pheromonal communication often involves providing information about the reproductive
status of a potential mate. So, for example, when a female rat is ready to mate, she secretes pheromonal
signals that draw attention from nearby male rats. Pheromonal activation is actually an important
component in eliciting sexual behavior in the male rat (Furlow, 1996, 2012; Purvis & Haynes, 1972; Sachs,
1997). There has also been a good deal of research (and controversy) about pheromones in humans
(Comfort, 1971; Russell, 1976; Wolfgang-Kimball, 1992; Weller, 1998).

TOUCH, THERMOCEPTION, AND NOCICEPTION

A number of receptors are distributed throughout the skin to respond to various touch-related stimuli
(Figure 5.23). These receptors include Meissner’s corpuscles, Pacinian corpuscles, Merkel’s disks, and
Ruffini corpuscles. Meissner’s corpuscles respond to pressure and lower frequency vibrations, and
Pacinian corpuscles detect transient pressure and higher frequency vibrations. Merkel’s disks respond to
light pressure, while Ruffini corpuscles detect stretch (Abraira & Ginty, 2013).

Figure 5.23 There are many types of sensory receptors located in the skin, each attuned to specific touch-related
stimuli.

In addition to the receptors located in the skin, there are also a number of free nerve endings that
serve sensory functions. These nerve endings respond to a variety of different types of touch-related
stimuli and serve as sensory receptors for both thermoception (temperature perception) and nociception
(a signal indicating potential harm and maybe pain) (Garland, 2012; Petho & Reeh, 2012; Spray, 1986).
Sensory information collected from the receptors and free nerve endings travels up the spinal cord and is
transmitted to regions of the medulla, thalamus, and ultimately to somatosensory cortex, which is located
in the postcentral gyrus of the parietal lobe.

Pain Perception

Pain is an unpleasant experience that involves both physical and psychological components. Feeling pain
is quite adaptive because it makes us aware of an injury, and it motivates us to remove ourselves from the
cause of that injury. In addition, pain also makes us less likely to suffer additional injury because we will
be gentler with our injured body parts.

Generally speaking, pain can be considered to be neuropathic or inflammatory in nature. Pain that signals
some type of tissue damage is known as inflammatory pain. In some situations, pain results from damage
to neurons of either the peripheral or central nervous system. As a result, pain signals that are sent to the

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brain get exaggerated. This type of pain is known as neuropathic pain. Multiple treatment options for pain
relief range from relaxation therapy to the use of analgesic medications to deep brain stimulation. The most
effective treatment option for a given individual will depend on a number of considerations, including the
severity and persistence of the pain and any medical/psychological conditions.

Some individuals are born without the ability to feel pain. This very rare genetic disorder is known as
congenital insensitivity to pain (or congenital analgesia). While those with congenital analgesia can
detect differences in temperature and pressure, they cannot experience pain. As a result, they often suffer
significant injuries. Young children have serious mouth and tongue injuries because they have bitten
themselves repeatedly. Not surprisingly, individuals suffering from this disorder have much shorter life
expectancies due to their injuries and secondary infections of injured sites (U.S. National Library of
Medicine, 2013).

Watch this video about congenital insensitivity to pain (http://openstax.org/l/congenital) to learn
more.

THE VESTIBULAR SENSE, PROPRIOCEPTION, AND KINESTHESIA

The vestibular sense contributes to our ability to maintain balance and body posture. As Figure 5.24
shows, the major sensory organs (utricle, saccule, and the three semicircular canals) of this system are
located next to the cochlea in the inner ear. The vestibular organs are fluid-filled and have hair cells, similar
to the ones found in the auditory system, which respond to movement of the head and gravitational forces.
When these hair cells are stimulated, they send signals to the brain via the vestibular nerve. Although we
may not be consciously aware of our vestibular system’s sensory information under normal circumstances,
its importance is apparent when we experience motion sickness and/or dizziness related to infections of
the inner ear (Khan & Chang, 2013).

Figure 5.24 The major sensory organs of the vestibular system are located next to the cochlea in the inner ear.
These include the utricle, saccule, and the three semicircular canals (posterior, superior, and horizontal).

In addition to maintaining balance, the vestibular system collects information critical for controlling
movement and the reflexes that move various parts of our bodies to compensate for changes in body

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position. Therefore, both proprioception (perception of body position) and kinesthesia (perception of the
body’s movement through space) interact with information provided by the vestibular system.

These sensory systems also gather information from receptors that respond to stretch and tension in
muscles, joints, skin, and tendons (Lackner & DiZio, 2005; Proske, 2006; Proske & Gandevia, 2012).
Proprioceptive and kinesthetic information travels to the brain via the spinal column. Several cortical
regions in addition to the cerebellum receive information from and send information to the sensory organs
of the proprioceptive and kinesthetic systems.

5.6 Gestalt Principles of Perception

Learning Objectives

By the end of this section, you will be able to:
• Explain the figure-ground relationship
• Define Gestalt principles of grouping
• Describe how perceptual set is influenced by an individual’s characteristics and mental state

In the early part of the 20th century, Max Wertheimer published a paper demonstrating that individuals
perceived motion in rapidly flickering static images—an insight that came to him as he used a child’s toy
tachistoscope. Wertheimer, and his assistants Wolfgang Köhler and Kurt Koffka, who later became his
partners, believed that perception involved more than simply combining sensory stimuli. This belief led to
a new movement within the field of psychology known as Gestalt psychology. The word gestalt literally
means form or pattern, but its use reflects the idea that the whole is different from the sum of its parts. In
other words, the brain creates a perception that is more than simply the sum of available sensory inputs,
and it does so in predictable ways. Gestalt psychologists translated these predictable ways into principles
by which we organize sensory information. As a result, Gestalt psychology has been extremely influential
in the area of sensation and perception (Rock & Palmer, 1990).

One Gestalt principle is the figure-ground relationship. According to this principle, we tend to segment
our visual world into figure and ground. Figure is the object or person that is the focus of the visual
field, while the ground is the background. As Figure 5.25 shows, our perception can vary tremendously,
depending on what is perceived as figure and what is perceived as ground. Presumably, our ability to
interpret sensory information depends on what we label as figure and what we label as ground in any
particular case, although this assumption has been called into question (Peterson & Gibson, 1994; Vecera
& O’Reilly, 1998).

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Figure 5.25 The concept of figure-ground relationship explains why this image can be perceived either as a vase or
as a pair of faces.

Another Gestalt principle for organizing sensory stimuli into meaningful perception is proximity. This
principle asserts that things that are close to one another tend to be grouped together, as Figure 5.26
illustrates.

Figure 5.26 The Gestalt principle of proximity suggests that you see (a) one block of dots on the left side and (b)
three columns on the right side.

How we read something provides another illustration of the proximity concept. For example, we read this
sentence like this, notl iket hiso rt hat. We group the letters of a given word together because there are no
spaces between the letters, and we perceive words because there are spaces between each word. Here are
some more examples: Cany oum akes enseo ft hiss entence? What doth es e wor dsmea n?

We might also use the principle of similarity to group things in our visual fields. According to this
principle, things that are alike tend to be grouped together (Figure 5.27). For example, when watching
a football game, we tend to group individuals based on the colors of their uniforms. When watching an
offensive drive, we can get a sense of the two teams simply by grouping along this dimension.

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Figure 5.27 When looking at this array of dots, we likely perceive alternating rows of colors. We are grouping these
dots according to the principle of similarity.

Two additional Gestalt principles are the law of continuity (or good continuation) and closure. The law
of continuity suggests that we are more likely to perceive continuous, smooth flowing lines rather than
jagged, broken lines (Figure 5.28). The principle of closure states that we organize our perceptions into
complete objects rather than as a series of parts (Figure 5.29).

Figure 5.28 Good continuation would suggest that we are more likely to perceive this as two overlapping lines,
rather than four lines meeting in the center.

Figure 5.29 Closure suggests that we will perceive a complete circle and rectangle rather than a series of
segments.

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Watch this video showing real world examples of Gestalt principles (http://openstax.org/l/gestalt) to
learn more.

According to Gestalt theorists, pattern perception, or our ability to discriminate among different figures
and shapes, occurs by following the principles described above. You probably feel fairly certain that
your perception accurately matches the real world, but this is not always the case. Our perceptions are
based on perceptual hypotheses: educated guesses that we make while interpreting sensory information.
These hypotheses are informed by a number of factors, including our personalities, experiences, and
expectations. We use these hypotheses to generate our perceptual set. For instance, research has
demonstrated that those who are given verbal priming produce a biased interpretation of complex
ambiguous figures (Goolkasian & Woodbury, 2010).

The Depths of Perception: Bias, Prejudice, and Cultural Factors

In this chapter, you have learned that perception is a complex process. Built from sensations, but influenced
by our own experiences, biases, prejudices, and cultures, perceptions can be very different from person
to person. Research suggests that implicit racial prejudice and stereotypes affect perception. For instance,
several studies have demonstrated that non-Black participants identify weapons faster and are more likely to
identify non-weapons as weapons when the image of the weapon is paired with the image of a Black person
(Payne, 2001; Payne, Shimizu, & Jacoby, 2005). Furthermore, White individuals’ decisions to shoot an armed
target in a video game is made more quickly when the target is Black (Correll, Park, Judd, & Wittenbrink, 2002;
Correll, Urland, & Ito, 2006). This research is important, considering the number of very high-profile cases in
the last few decades in which young Blacks were killed by people who claimed to believe that the unarmed
individuals were armed and/or represented some threat to their personal safety.

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DIG DEEPER

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absolute threshold

afterimage

amplitude

basilar membrane

binaural cue

binocular cue

binocular disparity

blind spot

bottom-up processing

closure

cochlea

cochlear implant

conductive hearing loss

cone

congenital deafness

congenital insensitivity to pain (congenital analgesia)

cornea

deafness

decibel (dB)

depth perception

electromagnetic spectrum

figure-ground relationship

fovea

frequency

Gestalt psychology

good continuation

Key Terms

minimum amount of stimulus energy that must be present for the stimulus to be
detected 50% of the time

continuation of a visual sensation after removal of the stimulus

height of a wave

thin strip of tissue within the cochlea that contains the hair cells which serve as the
sensory receptors for the auditory system

two-eared cue to localize sound

cue that relies on the use of both eyes

slightly different view of the world that each eye receives

point where we cannot respond to visual information in that portion of the visual field

system in which perceptions are built from sensory input

organizing our perceptions into complete objects rather than as a series of parts

fluid-filled, snail-shaped structure that contains the sensory receptor cells of the auditory system

electronic device that consists of a microphone, a speech processor, and an electrode
array to directly stimulate the auditory nerve to transmit information to the brain

failure in the vibration of the eardrum and/or movement of the ossicles

specialized photoreceptor that works best in bright light conditions and detects color

deafness from birth

genetic disorder that results in the inability to
experience pain

transparent covering over the eye

partial or complete inability to hear

logarithmic unit of sound intensity

ability to perceive depth

all the electromagnetic radiation that occurs in our environment

segmenting our visual world into figure and ground

small indentation in the retina that contains cones

number of waves that pass a given point in a given time period

field of psychology based on the idea that the whole is different from the sum of its
parts

(also, continuity) we are more likely to perceive continuous, smooth flowing lines

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hair cell

hertz (Hz)

inattentional blindness

incus

inflammatory pain

interaural level difference

interaural timing difference

iris

just noticeable difference

kinesthesia

lens

linear perspective

malleus

Meissner’s corpuscle

Merkel’s disk

monaural cue

monocular cue

Ménière’s disease

neuropathic pain

nociception

olfactory bulb

olfactory receptor

opponent-process theory of color perception

optic chiasm

optic nerve

Pacinian corpuscle

rather than jagged, broken lines

auditory receptor cell of the inner ear

cycles per second; measure of frequency

failure to notice something that is completely visible because of a lack of
attention

middle ear ossicle; also known as the anvil

signal that some type of tissue damage has occurred

sound coming from one side of the body is more intense at the closest ear
because of the attenuation of the sound wave as it passes through the head

small difference in the time at which a given sound wave arrives at each ear

colored portion of the eye

difference in stimuli required to detect a difference between the stimuli

perception of the body’s movement through space

curved, transparent structure that provides additional focus for light entering the eye

perceive depth in an image when two parallel lines seem to converge

middle ear ossicle; also known as the hammer

touch receptor that responds to pressure and lower frequency vibrations

touch receptor that responds to light touch

one-eared cue to localize sound

cue that requires only one eye

results in a degeneration of inner ear structures that can lead to hearing loss, tinnitus,
vertigo, and an increase in pressure within the inner ear

pain from damage to neurons of either the peripheral or central nervous system

sensory signal indicating potential harm and maybe pain

bulb-like structure at the tip of the frontal lobe, where the olfactory nerves begin

sensory cell for the olfactory system

color is coded in opponent pairs: black-white, yellow-blue,
and red-green

X-shaped structure that sits just below the brain’s ventral surface; represents the merging of
the optic nerves from the two eyes and the separation of information from the two sides of the visual field
to the opposite side of the brain

carries visual information from the retina to the brain

touch receptor that detects transient pressure and higher frequency vibrations

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pattern perception

peak

perception

perceptual hypothesis

pheromone

photoreceptor

pinna

pitch

place theory of pitch perception

principle of closure

proprioception

proximity

pupil

retina

rod

Ruffini corpuscle

sensation

sensorineural hearing loss

sensory adaptation

signal detection theory

similarity

stapes

subliminal message

taste bud

temporal theory of pitch perception

thermoception

timbre

top-down processing

ability to discriminate among different figures and shapes

(also, crest) highest point of a wave

way that sensory information is interpreted and consciously experienced

educated guess used to interpret sensory information

chemical message sent by another individual

light-detecting cell

visible part of the ear that protrudes from the head

perception of a sound’s frequency

different portions of the basilar membrane are sensitive to sounds of
different frequencies

organize perceptions into complete objects rather than as a series of parts

perception of body position

things that are close to one another tend to be grouped together

small opening in the eye through which light passes

light-sensitive lining of the eye

specialized photoreceptor that works well in low light conditions

touch receptor that detects stretch

what happens when sensory information is detected by a sensory receptor

failure to transmit neural signals from the cochlea to the brain

not perceiving stimuli that remain relatively constant over prolonged periods of time

change in stimulus detection as a function of current mental state

things that are alike tend to be grouped together

middle ear ossicle; also known as the stirrup

message presented below the threshold of conscious awareness

grouping of taste receptor cells with hair-like extensions that protrude into the central pore of
the taste bud

sound’s frequency is coded by the activity level of a sensory neuron

temperature perception

sound’s purity

interpretation of sensations is influenced by available knowledge, experiences, and
thoughts

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transduction

trichromatic theory of color perception

trough

tympanic membrane

umami

vertigo

vestibular sense

visible spectrum

wavelength

conversion from sensory stimulus energy to action potential

color vision is mediated by the activity across the three groups
of cones

lowest point of a wave

eardrum

taste for monosodium glutamate

spinning sensation

contributes to our ability to maintain balance and body posture

portion of the electromagnetic spectrum that we can see

length of a wave from one peak to the next peak

Summary

5.1 Sensation versus Perception
Sensation occurs when sensory receptors detect sensory stimuli. Perception involves the organization,
interpretation, and conscious experience of those sensations. All sensory systems have both absolute and
difference thresholds, which refer to the minimum amount of stimulus energy or the minimum amount
of difference in stimulus energy required to be detected about 50% of the time, respectively. Sensory
adaptation, selective attention, and signal detection theory can help explain what is perceived and what is
not. In addition, our perceptions are affected by a number of factors, including beliefs, values, prejudices,
culture, and life experiences.

5.2 Waves and Wavelengths
Both light and sound can be described in terms of wave forms with physical characteristics like amplitude,
wavelength, and timbre. Wavelength and frequency are inversely related so that longer waves have lower
frequencies, and shorter waves have higher frequencies. In the visual system, a light wave’s wavelength is
generally associated with color, and its amplitude is associated with brightness. In the auditory system, a
sound’s frequency is associated with pitch, and its amplitude is associated with loudness.

5.3 Vision
Light waves cross the cornea and enter the eye at the pupil. The eye’s lens focuses this light so that the
image is focused on a region of the retina known as the fovea. The fovea contains cones that possess
high levels of visual acuity and operate best in bright light conditions. Rods are located throughout the
retina and operate best under dim light conditions. Visual information leaves the eye via the optic nerve.
Information from each visual field is sent to the opposite side of the brain at the optic chiasm. Visual
information then moves through a number of brain sites before reaching the occipital lobe, where it is
processed.

Two theories explain color perception. The trichromatic theory asserts that three distinct cone groups are
tuned to slightly different wavelengths of light, and it is the combination of activity across these cone
types that results in our perception of all the colors we see. The opponent-process theory of color vision
asserts that color is processed in opponent pairs and accounts for the interesting phenomenon of a negative
afterimage. We perceive depth through a combination of monocular and binocular depth cues.

5.4 Hearing
Sound waves are funneled into the auditory canal and cause vibrations of the eardrum; these vibrations
move the ossicles. As the ossicles move, the stapes presses against the oval window of the cochlea, which

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causes fluid inside the cochlea to move. As a result, hair cells embedded in the basilar membrane become
enlarged, which sends neural impulses to the brain via the auditory nerve.

Pitch perception and sound localization are important aspects of hearing. Our ability to perceive pitch
relies on both the firing rate of the hair cells in the basilar membrane as well as their location within the
membrane. In terms of sound localization, both monaural and binaural cues are used to locate where
sounds originate in our environment.

Individuals can be born deaf, or they can develop deafness as a result of age, genetic predisposition, and/
or environmental causes. Hearing loss that results from a failure of the vibration of the eardrum or the
resultant movement of the ossicles is called conductive hearing loss. Hearing loss that involves a failure of
the transmission of auditory nerve impulses to the brain is called sensorineural hearing loss.

5.5 The Other Senses
Taste (gustation) and smell (olfaction) are chemical senses that employ receptors on the tongue and in the
nose that bind directly with taste and odor molecules in order to transmit information to the brain for
processing. Our ability to perceive touch, temperature, and pain is mediated by a number of receptors
and free nerve endings that are distributed throughout the skin and various tissues of the body. The
vestibular sense helps us maintain a sense of balance through the response of hair cells in the utricle,
saccule, and semi-circular canals that respond to changes in head position and gravity. Our proprioceptive
and kinesthetic systems provide information about body position and body movement through receptors
that detect stretch and tension in the muscles, joints, tendons, and skin of the body.

5.6 Gestalt Principles of Perception
Gestalt theorists have been incredibly influential in the areas of sensation and perception. Gestalt
principles such as figure-ground relationship, grouping by proximity or similarity, the law of good
continuation, and closure are all used to help explain how we organize sensory information. Our
perceptions are not infallible, and they can be influenced by bias, prejudice, and other factors.

Review Questions

1. ________ refers to the minimum amount of
stimulus energy required to be detected 50% of the
time.

a. absolute threshold
b. difference threshold
c. just noticeable difference
d. transduction

2. Decreased sensitivity to an unchanging
stimulus is known as ________.

a. transduction
b. difference threshold
c. sensory adaptation
d. inattentional blindness

3. ________ involves the conversion of sensory
stimulus energy into neural impulses.

a. sensory adaptation
b. inattentional blindness
c. difference threshold
d. transduction

4. ________ occurs when sensory information is
organized, interpreted, and consciously
experienced.

a. sensation
b. perception
c. transduction
d. sensory adaptation

5. Which of the following correctly matches the
pattern in our perception of color as we move
from short wavelengths to long wavelengths?

a. red to orange to yellow
b. yellow to orange to red
c. yellow to red to orange
d. orange to yellow to red

6. The visible spectrum includes light that ranges
from about ________.

a. 400–700 nm
b. 200–900 nm
c. 20–20000 Hz
d. 10–20 dB

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7. The electromagnetic spectrum includes
________.

a. radio waves
b. x-rays
c. infrared light
d. all of the above

8. The audible range for humans is ________.
a. 380–740 Hz
b. 10–20 dB
c. less than 300 dB
d. 20-20,000 Hz

9. The quality of a sound that is affected by
frequency, amplitude, and timing of the sound
wave is known as ________.

a. pitch
b. tone
c. electromagnetic
d. timbre

10. The ________ is a small indentation of the
retina that contains cones.

a. optic chiasm
b. optic nerve
c. fovea
d. iris

11. ________ operate best under bright light
conditions.

a. cones
b. rods
c. retinal ganglion cells
d. striate cortex

12. ________ depth cues require the use of both
eyes.

a. monocular
b. binocular
c. linear perspective
d. accommodating

13. If you were to stare at a green dot for a
relatively long period of time and then shift your
gaze to a blank white screen, you would see a
________ negative afterimage.

a. blue
b. yellow
c. black
d. red

14. Hair cells located near the base of the basilar
membrane respond best to ________ sounds.

a. low-frequency
b. high-frequency
c. low-amplitude
d. high-amplitude

15. The three ossicles of the middle ear are
known as ________.

a. malleus, incus, and stapes
b. hammer, anvil, and stirrup
c. pinna, cochlea, and utricle
d. both a and b

16. Hearing aids might be effective for treating
________.

a. Ménière’s disease
b. sensorineural hearing loss
c. conductive hearing loss
d. interaural time differences

17. Cues that require two ears are referred to as
________ cues.

a. monocular
b. monaural
c. binocular
d. binaural

18. Chemical messages often sent between two
members of a species to communicate something
about reproductive status are called ________.

a. hormones
b. pheromones
c. Merkel’s disks
d. Meissner’s corpuscles

19. Which taste is associated with monosodium
glutamate?

a. sweet
b. bitter
c. umami
d. sour

20. ________ serve as sensory receptors for
temperature and pain stimuli.

a. free nerve endings
b. Pacinian corpuscles
c. Ruffini corpuscles
d. Meissner’s corpuscles

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21. Which of the following is involved in
maintaining balance and body posture?

a. auditory nerve
b. nociceptors
c. olfactory bulb
d. vestibular system

22. According to the principle of ________,
objects that occur close to one another tend to be
grouped together.

a. similarity
b. good continuation
c. proximity
d. closure

23. Our tendency to perceive things as complete
objects rather than as a series of parts is known as
the principle of ________.

a. closure
b. good continuation
c. proximity
d. similarity

24. According to the law of ________, we are
more likely to perceive smoothly flowing lines
rather than choppy or jagged lines.

a. closure
b. good continuation
c. proximity
d. similarity

25. The main point of focus in a visual display is
known as the ________.

a. closure
b. perceptual set
c. ground
d. figure

Critical Thinking Questions

26. Not everything that is sensed is perceived. Do you think there could ever be a case where something
could be perceived without being sensed?

27. Please generate a novel example of how just noticeable difference can change as a function of stimulus
intensity.

28. Why do you think other species have such different ranges of sensitivity for both visual and auditory
stimuli compared to humans?

29. Why do you think humans are especially sensitive to sounds with frequencies that fall in the middle
portion of the audible range?

30. Compare the two theories of color perception. Are they completely different?

31. Color is not a physical property of our environment. What function (if any) do you think color vision
serves?

32. Given what you’ve read about sound localization, from an evolutionary perspective, how does sound
localization facilitate survival?

33. How can temporal and place theories both be used to explain our ability to perceive the pitch of sound
waves with frequencies up to 4000 Hz?

34. Many people experience nausea while traveling in a car, plane, or boat. How might you explain this
as a function of sensory interaction?

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35. If you heard someone say that they would do anything not to feel the pain associated with significant
injury, how would you respond given what you’ve just read?

36. Do you think women experience pain differently than men? Why do you think this is?

37. The central tenet of Gestalt psychology is that the whole is different from the sum of its parts. What
does this mean in the context of perception?

38. Take a look at the following figure. How might you influence whether people see a duck or a rabbit?

Figure 5.30

Personal Application Questions

39. Think about a time when you failed to notice something around you because your attention was
focused elsewhere. If someone pointed it out, were you surprised that you hadn’t noticed it right away?

40. If you grew up with a family pet, then you have surely noticed that they often seem to hear things that
you don’t hear. Now that you’ve read this section, you probably have some insight as to why this may be.
How would you explain this to a friend who never had the opportunity to take a class like this?

41. Take a look at a few of your photos or personal works of art. Can you find examples of linear
perspective as a potential depth cue?

42. If you had to choose to lose either your vision or your hearing, which would you choose and why?

43. As mentioned earlier, a food’s flavor represents an interaction of both gustatory and olfactory
information. Think about the last time you were seriously congested due to a cold or the flu. What changes
did you notice in the flavors of the foods that you ate during this time?

44. Have you ever listened to a song on the radio and sung along only to find out later that you have been
singing the wrong lyrics? Once you found the correct lyrics, did your perception of the song change?

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Chapter 6

Learning

Figure 6.1 Loggerhead sea turtle hatchlings are born knowing how to find the ocean and how to swim. Unlike the
sea turtle, humans must learn how to swim (and surf). (credit “turtle”: modification of work by Becky Skiba, USFWS;
credit “surfer”: modification of work by Mike Baird)

Chapter Outline

6.1 What Is Learning?

6.2 Classical Conditioning

6.3 Operant Conditioning

6.4 Observational Learning (Modeling)

Introduction

The summer sun shines brightly on a deserted stretch of beach. Suddenly, a tiny grey head emerges
from the sand, then another and another. Soon the beach is teeming with loggerhead sea turtle hatchlings
(Figure 6.1). Although only minutes old, the hatchlings know exactly what to do. Their flippers are not
very efficient for moving across the hot sand, yet they continue onward, instinctively. Some are quickly
snapped up by gulls circling overhead and others become lunch for hungry ghost crabs that dart out of
their holes. Despite these dangers, the hatchlings are driven to leave the safety of their nest and find the
ocean.

Not far down this same beach, Ben and his son, Julian, paddle out into the ocean on surfboards. A wave
approaches. Julian crouches on his board, then jumps up and rides the wave for a few seconds before
losing his balance. He emerges from the water in time to watch his father ride the face of the wave.

Unlike baby sea turtles, which know how to find the ocean and swim with no help from their parents, we
are not born knowing how to swim (or surf). Yet we humans pride ourselves on our ability to learn. In fact,
over thousands of years and across cultures, we have created institutions devoted entirely to learning. But
have you ever asked yourself how exactly it is that we learn? What processes are at work as we come to
know what we know? This chapter focuses on the primary ways in which learning occurs.

Chapter 6 | Learning 191

6.1 What Is Learning?

Learning Objectives

By the end of this section, you will be able to:
• Explain how learned behaviors are different from instincts and reflexes
• Define learning
• Recognize and define three basic forms of learning—classical conditioning, operant

conditioning, and observational learning

Birds build nests and migrate as winter approaches. Infants suckle at their mother’s breast. Dogs shake
water off wet fur. Salmon swim upstream to spawn, and spiders spin intricate webs. What do these
seemingly unrelated behaviors have in common? They all are unlearned behaviors. Both instincts and
reflexes are innate (unlearned) behaviors that organisms are born with. Reflexes are a motor or neural
reaction to a specific stimulus in the environment. They tend to be simpler than instincts, involve the
activity of specific body parts and systems (e.g., the knee-jerk reflex and the contraction of the pupil in
bright light), and involve more primitive centers of the central nervous system (e.g., the spinal cord and the
medulla). In contrast, instincts are innate behaviors that are triggered by a broader range of events, such
as maturation and the change of seasons. They are more complex patterns of behavior, involve movement
of the organism as a whole (e.g., sexual activity and migration), and involve higher brain centers.

Both reflexes and instincts help an organism adapt to its environment and do not have to be learned. For
example, every healthy human baby has a sucking reflex, present at birth. Babies are born knowing how to
suck on a nipple, whether artificial (from a bottle) or human. Nobody teaches the baby to suck, just as no
one teaches a sea turtle hatchling to move toward the ocean. Learning, like reflexes and instincts, allows an
organism to adapt to its environment. But unlike instincts and reflexes, learned behaviors involve change
and experience: learning is a relatively permanent change in behavior or knowledge that results from
experience. In contrast to the innate behaviors discussed above, learning involves acquiring knowledge
and skills through experience. Looking back at our surfing scenario, Julian will have to spend much more
time training with his surfboard before he learns how to ride the waves like his father.

Learning to surf, as well as any complex learning process (e.g., learning about the discipline of
psychology), involves a complex interaction of conscious and unconscious processes. Learning has
traditionally been studied in terms of its simplest components—the associations our minds automatically
make between events. Our minds have a natural tendency to connect events that occur closely together or
in sequence. Associative learning occurs when an organism makes connections between stimuli or events
that occur together in the environment. You will see that associative learning is central to all three basic
learning processes discussed in this chapter; classical conditioning tends to involve unconscious processes,
operant conditioning tends to involve conscious processes, and observational learning adds social and
cognitive layers to all the basic associative processes, both conscious and unconscious. These learning
processes will be discussed in detail later in the chapter, but it is helpful to have a brief overview of each
as you begin to explore how learning is understood from a psychological perspective.

In classical conditioning, also known as Pavlovian conditioning, organisms learn to associate events—or
stimuli—that repeatedly happen together. We experience this process throughout our daily lives. For
example, you might see a flash of lightning in the sky during a storm and then hear a loud boom of
thunder. The sound of the thunder naturally makes you jump (loud noises have that effect by reflex).
Because lightning reliably predicts the impending boom of thunder, you may associate the two and jump
when you see lightning. Psychological researchers study this associative process by focusing on what can
be seen and measured—behaviors. Researchers ask if one stimulus triggers a reflex, can we train a different
stimulus to trigger that same reflex? In operant conditioning, organisms learn, again, to associate events—a
behavior and its consequence (reinforcement or punishment). A pleasant consequence encourages more

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of that behavior in the future, whereas a punishment deters the behavior. Imagine you are teaching your
dog, Hodor, to sit. You tell Hodor to sit, and give him a treat when he does. After repeated experiences,
Hodor begins to associate the act of sitting with receiving a treat. He learns that the consequence of sitting
is that he gets a doggie biscuit (Figure 6.2). Conversely, if the dog is punished when exhibiting a behavior,
it becomes conditioned to avoid that behavior (e.g., receiving a small shock when crossing the boundary
of an invisible electric fence).

Figure 6.2 In operant conditioning, a response is associated with a consequence. This dog has learned that certain
behaviors result in receiving a treat. (credit: Crystal Rolfe)

Observational learning extends the effective range of both classical and operant conditioning. In contrast to
classical and operant conditioning, in which learning occurs only through direct experience, observational
learning is the process of watching others and then imitating what they do. A lot of learning among
humans and other animals comes from observational learning. To get an idea of the extra effective range
that observational learning brings, consider Ben and his son Julian from the introduction. How might
observation help Julian learn to surf, as opposed to learning by trial and error alone? By watching his
father, he can imitate the moves that bring success and avoid the moves that lead to failure. Can you think
of something you have learned how to do after watching someone else?

All of the approaches covered in this chapter are part of a particular tradition in psychology, called
behaviorism, which we discuss in the next section. However, these approaches do not represent the entire
study of learning. Separate traditions of learning have taken shape within different fields of psychology,
such as memory and cognition, so you will find that other chapters will round out your understanding
of the topic. Over time these traditions tend to converge. For example, in this chapter you will see how
cognition has come to play a larger role in behaviorism, whose more extreme adherents once insisted that
behaviors are triggered by the environment with no intervening thought.

6.2 Classical Conditioning

Learning Objectives

By the end of this section, you will be able to:
• Explain how classical conditioning occurs
• Summarize the processes of acquisition, extinction, spontaneous recovery, generalization,

and discrimination

Does the name Ivan Pavlov ring a bell? Even if you are new to the study of psychology, chances are that
you have heard of Pavlov and his famous dogs.

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Pavlov (1849–1936), a Russian scientist, performed extensive research on dogs and is best known for
his experiments in classical conditioning (Figure 6.3). As we discussed briefly in the previous section,
classical conditioning is a process by which we learn to associate stimuli and, consequently, to anticipate
events.

Figure 6.3 Ivan Pavlov’s research on the digestive system of dogs unexpectedly led to his discovery of the learning
process now known as classical conditioning.

Pavlov came to his conclusions about how learning occurs completely by accident. Pavlov was a
physiologist, not a psychologist. Physiologists study the life processes of organisms, from the molecular
level to the level of cells, organ systems, and entire organisms. Pavlov’s area of interest was the digestive
system (Hunt, 2007). In his studies with dogs, Pavlov measured the amount of saliva produced in response
to various foods. Over time, Pavlov (1927) observed that the dogs began to salivate not only at the taste
of food, but also at the sight of food, at the sight of an empty food bowl, and even at the sound of the
laboratory assistants’ footsteps. Salivating to food in the mouth is reflexive, so no learning is involved.
However, dogs don’t naturally salivate at the sight of an empty bowl or the sound of footsteps.

These unusual responses intrigued Pavlov, and he wondered what accounted for what he called the dogs’
“psychic secretions” (Pavlov, 1927). To explore this phenomenon in an objective manner, Pavlov designed
a series of carefully controlled experiments to see which stimuli would cause the dogs to salivate. He was
able to train the dogs to salivate in response to stimuli that clearly had nothing to do with food, such as the
sound of a bell, a light, and a touch on the leg. Through his experiments, Pavlov realized that an organism
has two types of responses to its environment: (1) unconditioned (unlearned) responses, or reflexes, and
(2) conditioned (learned) responses.

In Pavlov’s experiments, the dogs salivated each time meat powder was presented to them. The meat
powder in this situation was an unconditioned stimulus (UCS): a stimulus that elicits a reflexive response
in an organism. The dogs’ salivation was an unconditioned response (UCR): a natural (unlearned)
reaction to a given stimulus. Before conditioning, think of the dogs’ stimulus and response like this:

Meat powder (UCS) → Salivation (UCR)

In classical conditioning, a neutral stimulus is presented immediately before an unconditioned stimulus.
Pavlov would sound a tone (like ringing a bell) and then give the dogs the meat powder (Figure 6.4). The
tone was the neutral stimulus (NS), which is a stimulus that does not naturally elicit a response. Prior to
conditioning, the dogs did not salivate when they just heard the tone because the tone had no association
for the dogs.

Tone (NS) + Meat Powder (UCS) → Salivation (UCR)

When Pavlov paired the tone with the meat powder over and over again, the previously neutral stimulus
(the tone) also began to elicit salivation from the dogs. Thus, the neutral stimulus became the conditioned

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stimulus (CS), which is a stimulus that elicits a response after repeatedly being paired with an
unconditioned stimulus. Eventually, the dogs began to salivate to the tone alone, just as they previously
had salivated at the sound of the assistants’ footsteps. The behavior caused by the conditioned stimulus is
called the conditioned response (CR). In the case of Pavlov’s dogs, they had learned to associate the tone
(CS) with being fed, and they began to salivate (CR) in anticipation of food.

Tone (CS) → Salivation (CR)

Figure 6.4 Before conditioning, an unconditioned stimulus (food) produces an unconditioned response (salivation),
and a neutral stimulus (bell) does not produce a response. During conditioning, the unconditioned stimulus (food) is
presented repeatedly just after the presentation of the neutral stimulus (bell). After conditioning, the neutral stimulus
alone produces a conditioned response (salivation), thus becoming a conditioned stimulus.

View this video about Pavlov and his dogs (http://openstax.org/l/pavlov2) to learn more.

REAL WORLD APPLICATION OF CLASSICAL CONDITIONING

How does classical conditioning work in the real world? Consider the case of Moisha, who was diagnosed
with cancer. When she received her first chemotherapy treatment, she vomited shortly after the chemicals
were injected. In fact, every trip to the doctor for chemotherapy treatment shortly after the drugs were
injected, she vomited. Moisha’s treatment was a success and her cancer went into remission. Now, when
she visits her oncologist’s office every 6 months for a check-up, she becomes nauseous. In this case,
the chemotherapy drugs are the unconditioned stimulus (UCS), vomiting is the unconditioned response
(UCR), the doctor’s office is the conditioned stimulus (CS) after being paired with the UCS, and nausea
is the conditioned response (CR). Let’s assume that the chemotherapy drugs that Moisha takes are given
through a syringe injection. After entering the doctor’s office, Moisha sees a syringe, and then gets
her medication. In addition to the doctor’s office, Moisha will learn to associate the syringe will the
medication and will respond to syringes with nausea. This is an example of higher-order (or second-order)

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conditioning, when the conditioned stimulus (the doctor’s office) serves to condition another stimulus (the
syringe). It is hard to achieve anything above second-order conditioning. For example, if someone rang a
bell every time Moisha received a syringe injection of chemotherapy drugs in the doctor’s office, Moisha
likely will never get sick in response to the bell.

Consider another example of classical conditioning. Let’s say you have a cat named Tiger, who is quite
spoiled. You keep her food in a separate cabinet, and you also have a special electric can opener that you
use only to open cans of cat food. For every meal, Tiger hears the distinctive sound of the electric can
opener (“zzhzhz”) and then gets her food. Tiger quickly learns that when she hears “zzhzhz” she is about
to get fed. What do you think Tiger does when she hears the electric can opener? She will likely get excited
and run to where you are preparing her food. This is an example of classical conditioning. In this case,
what are the UCS, CS, UCR, and CR?

What if the cabinet holding Tiger’s food becomes squeaky? In that case, Tiger hears “squeak” (the cabinet),
“zzhzhz” (the electric can opener), and then she gets her food. Tiger will learn to get excited when she
hears the “squeak” of the cabinet. Pairing a new neutral stimulus (“squeak”) with the conditioned stimulus
(“zzhzhz”) is called higher-order conditioning, or second-order conditioning. This means you are using
the conditioned stimulus of the can opener to condition another stimulus: the squeaky cabinet (Figure 6.5).
It is hard to achieve anything above second-order conditioning. For example, if you ring a bell, open the
cabinet (“squeak”), use the can opener (“zzhzhz”), and then feed Tiger, Tiger will likely never get excited
when hearing the bell alone.

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Figure 6.5 In higher-order conditioning, an established conditioned stimulus is paired with a new neutral stimulus
(the second-order stimulus), so that eventually the new stimulus also elicits the conditioned response, without the
initial conditioned stimulus being presented.

Classical Conditioning at Stingray City

Kate and her spouse recently vacationed in the Cayman Islands, and booked a boat tour to Stingray City,
where they could feed and swim with the southern stingrays. The boat captain explained how the normally
solitary stingrays have become accustomed to interacting with humans. About 40 years ago, fishermen began
to clean fish and conch (unconditioned stimulus) at a particular sandbar near a barrier reef, and large numbers
of stingrays would swim in to eat (unconditioned response) what the fishermen threw into the water; this
continued for years. By the late 1980s, word of the large group of stingrays spread among scuba divers, who
then started feeding them by hand. Over time, the southern stingrays in the area were classically conditioned
much like Pavlov’s dogs. When they hear the sound of a boat engine (neutral stimulus that becomes a
conditioned stimulus), they know that they will get to eat (conditioned response).

As soon as they reached Stingray City, over two dozen stingrays surrounded their tour boat. The couple slipped
into the water with bags of squid, the stingrays’ favorite treat. The swarm of stingrays bumped and rubbed
up against their legs like hungry cats (Figure 6.6). Kate was able to feed, pet, and even kiss (for luck) these
amazing creatures. Then all the squid was gone, and so were the stingrays.

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Figure 6.6 Kate holds a southern stingray at Stingray City in the Cayman Islands. These stingrays have
been classically conditioned to associate the sound of a boat motor with food provided by tourists. (credit:
Kathryn Dumper)

Classical conditioning also applies to humans, even babies. For example, Sara buys formula in blue
canisters for her six-month-old daughter, Angelina. Whenever Sara takes out a formula container,
Angelina gets excited, tries to reach toward the food, and most likely salivates. Why does Angelina get
excited when she sees the formula canister? What are the UCS, CS, UCR, and CR here?

So far, all of the examples have involved food, but classical conditioning extends beyond the basic need
to be fed. Consider our earlier example of a dog whose owners install an invisible electric dog fence.
A small electrical shock (unconditioned stimulus) elicits discomfort (unconditioned response). When the
unconditioned stimulus (shock) is paired with a neutral stimulus (the edge of a yard), the dog associates
the discomfort (unconditioned response) with the edge of the yard (conditioned stimulus) and stays within
the set boundaries. In this example, the edge of the yard elicits fear and anxiety in the dog. Fear and anxiety
are the conditioned response.

Watch this video clip from the television show, The Office, for a humorous look at conditioning
(http://openstax.org/l/theoffice) in which Jim conditions Dwight to expect a breath mint every time Jim’s
computer makes a specific sound.

GENERAL PROCESSES IN CLASSICAL CONDITIONING

Now that you know how classical conditioning works and have seen several examples, let’s take a look at
some of the general processes involved. In classical conditioning, the initial period of learning is known
as acquisition, when an organism learns to connect a neutral stimulus and an unconditioned stimulus.
During acquisition, the neutral stimulus begins to elicit the conditioned response, and eventually the
neutral stimulus becomes a conditioned stimulus capable of eliciting the conditioned response by itself.
Timing is important for conditioning to occur. Typically, there should only be a brief interval between
presentation of the conditioned stimulus and the unconditioned stimulus. Depending on what is being

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conditioned, sometimes this interval is as little as five seconds (Chance, 2009). However, with other types
of conditioning, the interval can be up to several hours.

Taste aversion is a type of conditioning in which an interval of several hours may pass between the
conditioned stimulus (something ingested) and the unconditioned stimulus (nausea or illness). Here’s how
it works. Between classes, you and a friend grab a quick lunch from a food cart on campus. You share a
dish of chicken curry and head off to your next class. A few hours later, you feel nauseous and become ill.
Although your friend is fine and you determine that you have intestinal flu (the food is not the culprit),
you’ve developed a taste aversion; the next time you are at a restaurant and someone orders curry, you
immediately feel ill. While the chicken dish is not what made you sick, you are experiencing taste aversion:
you’ve been conditioned to be averse to a food after a single, bad experience.

How does this occur—conditioning based on a single instance and involving an extended time lapse
between the event and the negative stimulus? Research into taste aversion suggests that this response
may be an evolutionary adaptation designed to help organisms quickly learn to avoid harmful foods
(Garcia & Rusiniak, 1980; Garcia & Koelling, 1966). Not only may this contribute to species survival via
natural selection, but it may also help us develop strategies for challenges such as helping cancer patients
through the nausea induced by certain treatments (Holmes, 1993; Jacobsen et al., 1993; Hutton, Baracos, &
Wismer, 2007; Skolin et al., 2006). Garcia and Koelling (1966) showed not only that taste aversions could
be conditioned, but also that there were biological constraints to learning. In their study, separate groups
of rats were conditioned to associate either a flavor with illness, or lights and sounds with illness. Results
showed that all rats exposed to flavor-illness pairings learned to avoid the flavor, but none of the rats
exposed to lights and sounds with illness learned to avoid lights or sounds. This added evidence to the
idea that classical conditioning could contribute to species survival by helping organisms learn to avoid
stimuli that posed real dangers to health and welfare.

Robert Rescorla demonstrated how powerfully an organism can learn to predict the UCS from the CS.
Take, for example, the following two situations. Ari’s dad always has dinner on the table every day at 6:00.
Soraya’s mom switches it up so that some days they eat dinner at 6:00, some days they eat at 5:00, and
other days they eat at 7:00. For Ari, 6:00 reliably and consistently predicts dinner, so Ari will likely start
feeling hungry every day right before 6:00, even if he’s had a late snack. Soraya, on the other hand, will be
less likely to associate 6:00 with dinner, since 6:00 does not always predict that dinner is coming. Rescorla,
along with his colleague at Yale University, Alan Wagner, developed a mathematical formula that could
be used to calculate the probability that an association would be learned given the ability of a conditioned
stimulus to predict the occurrence of an unconditioned stimulus and other factors; today this is known as
the Rescorla-Wagner model (Rescorla & Wagner, 1972)

Once we have established the connection between the unconditioned stimulus and the conditioned
stimulus, how do we break that connection and get the dog, cat, or child to stop responding? In Tiger’s
case, imagine what would happen if you stopped using the electric can opener for her food and began to
use it only for human food. Now, Tiger would hear the can opener, but she would not get food. In classical
conditioning terms, you would be giving the conditioned stimulus, but not the unconditioned stimulus.
Pavlov explored this scenario in his experiments with dogs: sounding the tone without giving the dogs the
meat powder. Soon the dogs stopped responding to the tone. Extinction is the decrease in the conditioned
response when the unconditioned stimulus is no longer presented with the conditioned stimulus. When
presented with the conditioned stimulus alone, the dog, cat, or other organism would show a weaker and
weaker response, and finally no response. In classical conditioning terms, there is a gradual weakening
and disappearance of the conditioned response.

What happens when learning is not used for a while—when what was learned lies dormant? As we
just discussed, Pavlov found that when he repeatedly presented the bell (conditioned stimulus) without
the meat powder (unconditioned stimulus), extinction occurred; the dogs stopped salivating to the bell.
However, after a couple of hours of resting from this extinction training, the dogs again began to salivate
when Pavlov rang the bell. What do you think would happen with Tiger’s behavior if your electric can
opener broke, and you did not use it for several months? When you finally got it fixed and started using

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it to open Tiger’s food again, Tiger would remember the association between the can opener and her
food—she would get excited and run to the kitchen when she heard the sound. The behavior of Pavlov’s
dogs and Tiger illustrates a concept Pavlov called spontaneous recovery: the return of a previously
extinguished conditioned response following a rest period (Figure 6.7).

Figure 6.7 This is the curve of acquisition, extinction, and spontaneous recovery. The rising curve shows the
conditioned response quickly getting stronger through the repeated pairing of the conditioned stimulus and the
unconditioned stimulus (acquisition). Then the curve decreases, which shows how the conditioned response weakens
when only the conditioned stimulus is presented (extinction). After a break or pause from conditioning, the
conditioned response reappears (spontaneous recovery).

Of course, these processes also apply in humans. For example, let’s say that every day when you walk to
campus, an ice cream truck passes your route. Day after day, you hear the truck’s music (neutral stimulus),
so you finally stop and purchase a chocolate ice cream bar. You take a bite (unconditioned stimulus) and
then your mouth waters (unconditioned response). This initial period of learning is known as acquisition,
when you begin to connect the neutral stimulus (the sound of the truck) and the unconditioned stimulus
(the taste of the chocolate ice cream in your mouth). During acquisition, the conditioned response gets
stronger and stronger through repeated pairings of the conditioned stimulus and unconditioned stimulus.
Several days (and ice cream bars) later, you notice that your mouth begins to water (conditioned response)
as soon as you hear the truck’s musical jingle—even before you bite into the ice cream bar. Then one day
you head down the street. You hear the truck’s music (conditioned stimulus), and your mouth waters
(conditioned response). However, when you get to the truck, you discover that they are all out of ice cream.
You leave disappointed. The next few days you pass by the truck and hear the music, but don’t stop to
get an ice cream bar because you’re running late for class. You begin to salivate less and less when you
hear the music, until by the end of the week, your mouth no longer waters when you hear the tune. This
illustrates extinction. The conditioned response weakens when only the conditioned stimulus (the sound
of the truck) is presented, without being followed by the unconditioned stimulus (chocolate ice cream in
the mouth). Then the weekend comes. You don’t have to go to class, so you don’t pass the truck. Monday
morning arrives and you take your usual route to campus. You round the corner and hear the truck again.
What do you think happens? Your mouth begins to water again. Why? After a break from conditioning,
the conditioned response reappears, which indicates spontaneous recovery.

Acquisition and extinction involve the strengthening and weakening, respectively, of a learned
association. Two other learning processes—stimulus discrimination and stimulus generalization—are
involved in determining which stimuli will trigger learned responses. Animals (including humans) need
to distinguish between stimuli—for example, between sounds that predict a threatening event and sounds
that do not—so that they can respond appropriately (such as running away if the sound is threatening).
When an organism learns to respond differently to various stimuli that are similar, it is called stimulus
discrimination. In classical conditioning terms, the organism demonstrates the conditioned response only

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to the conditioned stimulus. Pavlov’s dogs discriminated between the basic tone that sounded before they
were fed and other tones (e.g., the doorbell), because the other sounds did not predict the arrival of food.
Similarly, Tiger, the cat, discriminated between the sound of the can opener and the sound of the electric
mixer. When the electric mixer is going, Tiger is not about to be fed, so she does not come running to
the kitchen looking for food. In our other example, Moisha, the cancer patient, discriminated between
oncologists and other types of doctors. She learned not to feel ill when visiting doctors for other types of
appointments, such as her annual physical.

On the other hand, when an organism demonstrates the conditioned response to stimuli that are similar to
the condition stimulus, it is called stimulus generalization, the opposite of stimulus discrimination. The
more similar a stimulus is to the condition stimulus, the more likely the organism is to give the conditioned
response. For instance, if the electric mixer sounds very similar to the electric can opener, Tiger may come
running after hearing its sound. But if you do not feed her following the electric mixer sound, and you
continue to feed her consistently after the electric can opener sound, she will quickly learn to discriminate
between the two sounds (provided they are sufficiently dissimilar that she can tell them apart). In our
other example, Moisha continued to feel ill whenever visiting other oncologists or other doctors in the
same building as her oncologist.

BEHAVIORISM

John B. Watson, shown in Figure 6.8, is considered the founder of behaviorism. Behaviorism is a school
of thought that arose during the first part of the 20th century, which incorporates elements of Pavlov’s
classical conditioning (Hunt, 2007). In stark contrast with Freud, who considered the reasons for behavior
to be hidden in the unconscious, Watson championed the idea that all behavior can be studied as a
simple stimulus-response reaction, without regard for internal processes. Watson argued that in order for
psychology to become a legitimate science, it must shift its concern away from internal mental processes
because mental processes cannot be seen or measured. Instead, he asserted that psychology must focus on
outward observable behavior that can be measured.

Figure 6.8 John B. Watson used the principles of classical conditioning in the study of human emotion.

Watson’s ideas were influenced by Pavlov’s work. According to Watson, human behavior, just like animal
behavior, is primarily the result of conditioned responses. Whereas Pavlov’s work with dogs involved the
conditioning of reflexes, Watson believed the same principles could be extended to the conditioning of
human emotions (Watson, 1919). Thus began Watson’s work with his graduate student Rosalie Rayner
and a baby called Little Albert. Through their experiments with Little Albert, Watson and Rayner (1920)
demonstrated how fears can be conditioned.

In 1920, Watson was the chair of the psychology department at Johns Hopkins University. Through his
position at the university he came to meet Little Albert’s mother, Arvilla Merritte, who worked at a campus

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hospital (DeAngelis, 2010). Watson offered her a dollar to allow her son to be the subject of his experiments
in classical conditioning. Through these experiments, Little Albert was exposed to and conditioned to fear
certain things. Initially he was presented with various neutral stimuli, including a rabbit, a dog, a monkey,
masks, cotton wool, and a white rat. He was not afraid of any of these things. Then Watson, with the
help of Rayner, conditioned Little Albert to associate these stimuli with an emotion—fear. For example,
Watson handed Little Albert the white rat, and Little Albert enjoyed playing with it. Then Watson made
a loud sound, by striking a hammer against a metal bar hanging behind Little Albert’s head, each time
Little Albert touched the rat. Little Albert was frightened by the sound—demonstrating a reflexive fear of
sudden loud noises—and began to cry. Watson repeatedly paired the loud sound with the white rat. Soon
Little Albert became frightened by the white rat alone. In this case, what are the UCS, CS, UCR, and CR?
Days later, Little Albert demonstrated stimulus generalization—he became afraid of other furry things:
a rabbit, a furry coat, and even a Santa Claus mask (Figure 6.9). Watson had succeeded in conditioning
a fear response in Little Albert, thus demonstrating that emotions could become conditioned responses.
It had been Watson’s intention to produce a phobia—a persistent, excessive fear of a specific object or
situation— through conditioning alone, thus countering Freud’s view that phobias are caused by deep,
hidden conflicts in the mind. However, there is no evidence that Little Albert experienced phobias in later
years. Little Albert’s mother moved away, ending the experiment. While Watson’s research provided new
insight into conditioning, it would be considered unethical by today’s standards.

Figure 6.9 Through stimulus generalization, Little Albert came to fear furry things, including Watson in a Santa
Claus mask.

View scenes from this video on John Watson’s experiment in which Little Albert was conditioned to
respond in fear to furry objects (http://openstax.org/l/Watson1) to learn more.

As you watch the video, look closely at Little Albert’s reactions and the manner in which Watson and
Rayner present the stimuli before and after conditioning. Based on what you see, would you come to the
same conclusions as the researchers?

Advertising and Associative Learning

Advertising executives are pros at applying the principles of associative learning. Think about the car
commercials you have seen on television. Many of them feature an attractive model. By associating the model
with the car being advertised, you come to see the car as being desirable (Cialdini, 2008). You may be asking
yourself, does this advertising technique actually work? According to Cialdini (2008), men who viewed a car
commercial that included an attractive model later rated the car as being faster, more appealing, and better

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designed than did men who viewed an advertisement for the same car minus the model.

Have you ever noticed how quickly advertisers cancel contracts with a famous athlete following a scandal?
As far as the advertiser is concerned, that athlete is no longer associated with positive feelings; therefore, the
athlete cannot be used as an unconditioned stimulus to condition the public to associate positive feelings (the
unconditioned response) with their product (the conditioned stimulus).

Now that you are aware of how associative learning works, see if you can find examples of these types of
advertisements on television, in magazines, or on the Internet.

6.3 Operant Conditioning

Learning Objectives

By the end of this section, you will be able to:
• Define operant conditioning
• Explain the difference between reinforcement and punishment
• Distinguish between reinforcement schedules

The previous section of this chapter focused on the type of associative learning known as classical
conditioning. Remember that in classical conditioning, something in the environment triggers a reflex
automatically, and researchers train the organism to react to a different stimulus. Now we turn to the
second type of associative learning, operant conditioning. In operant conditioning, organisms learn to
associate a behavior and its consequence (Table 6.1). A pleasant consequence makes that behavior more
likely to be repeated in the future. For example, Spirit, a dolphin at the National Aquarium in Baltimore,
does a flip in the air when her trainer blows a whistle. The consequence is that she gets a fish.

Classical and Operant Conditioning Compared

Classical Conditioning Operant Conditioning

Conditioning
approach

An unconditioned stimulus (such as
food) is paired with a neutral
stimulus (such as a bell). The neutral
stimulus eventually becomes the
conditioned stimulus, which brings
about the conditioned response
(salivation).

The target behavior is followed by
reinforcement or punishment to
either strengthen or weaken it, so
that the learner is more likely to
exhibit the desired behavior in the
future.

Stimulus timing The stimulus occurs immediately
before the response.

The stimulus (either reinforcement
or punishment) occurs soon after the
response.

Table 6.1

Psychologist B. F. Skinner saw that classical conditioning is limited to existing behaviors that are
reflexively elicited, and it doesn’t account for new behaviors such as riding a bike. He proposed a theory
about how such behaviors come about. Skinner believed that behavior is motivated by the consequences
we receive for the behavior: the reinforcements and punishments. His idea that learning is the result of

Chapter 6 | Learning 203

consequences is based on the law of effect, which was first proposed by psychologist Edward Thorndike.
According to the law of effect, behaviors that are followed by consequences that are satisfying to the
organism are more likely to be repeated, and behaviors that are followed by unpleasant consequences are
less likely to be repeated (Thorndike, 1911). Essentially, if an organism does something that brings about
a desired result, the organism is more likely to do it again. If an organism does something that does not
bring about a desired result, the organism is less likely to do it again. An example of the law of effect is in
employment. One of the reasons (and often the main reason) we show up for work is because we get paid
to do so. If we stop getting paid, we will likely stop showing up—even if we love our job.

Working with Thorndike’s law of effect as his foundation, Skinner began conducting scientific experiments
on animals (mainly rats and pigeons) to determine how organisms learn through operant conditioning
(Skinner, 1938). He placed these animals inside an operant conditioning chamber, which has come to be
known as a “Skinner box” (Figure 6.10). A Skinner box contains a lever (for rats) or disk (for pigeons) that
the animal can press or peck for a food reward via the dispenser. Speakers and lights can be associated
with certain behaviors. A recorder counts the number of responses made by the animal.

Figure 6.10 (a) B. F. Skinner developed operant conditioning for systematic study of how behaviors are
strengthened or weakened according to their consequences. (b) In a Skinner box, a rat presses a lever in an operant
conditioning chamber to receive a food reward. (credit a: modification of work by “Silly rabbit”/Wikimedia Commons)

Watch this brief video to see Skinner’s interview and a demonstration of operant conditioning of
pigeons (http://openstax.org/l/skinner1) to learn more.

In discussing operant conditioning, we use several everyday words—positive, negative, reinforcement,
and punishment—in a specialized manner. In operant conditioning, positive and negative do not mean
good and bad. Instead, positive means you are adding something, and negative means you are taking
something away. Reinforcement means you are increasing a behavior, and punishment means you are
decreasing a behavior. Reinforcement can be positive or negative, and punishment can also be positive
or negative. All reinforcers (positive or negative) increase the likelihood of a behavioral response. All
punishers (positive or negative) decrease the likelihood of a behavioral response. Now let’s combine
these four terms: positive reinforcement, negative reinforcement, positive punishment, and negative
punishment (Table 6.2).

LINK TO LEARNING

204 Chapter 6 | Learning

This OpenStax book is available for free at http://cnx.org/content/col31502/1.4

Positive and Negative Reinforcement and Punishment

Reinforcement Punishment

Positive Something is added to increase the
likelihood of a behavior.

Something is added to decrease the
likelihood of a behavior.

Negative Something is removed to increase the
likelihood of a behavior.

Something is removed to decrease the
likelihood of a behavior.

Table 6.2

REINFORCEMENT

The most effective way to teach a person or animal a new behavior is with positive reinforcement. In
positive reinforcement, a desirable stimulus is added to increase a behavior.

For example, you tell your five-year-old son, Jerome, that if he cleans his room, he will get a toy. Jerome
quickly cleans his room because he wants a new art set. Let’s pause for a moment. Some people might
say, “Why should I reward my child for doing what is expected?” But in fact we are constantly and
consistently rewarded in our lives. Our paychecks are rewards, as are high grades and acceptance into
our preferred school. Being praised for doing a good job and for passing a driver’s test is also a reward.
Positive reinforcement as a learning tool is extremely effective. It has been found that one of the most
effective ways to increase achievement in school districts with below-average reading scores was to pay
the children to read. Specifically, second-grade students in Dallas were paid $2 each time they read a book
and passed a short quiz about the book. The result was a significant increase in reading comprehension
(Fryer, 2010). What do you think about this program? If Skinner were alive today, he would probably
think this was a great idea. He was a strong proponent of using operant conditioning principles to
influence students’ behavior at school. In fact, in addition to the Skinner box, he also invented what
he called a teaching machine that was designed to reward small steps in learning (Skinner, 1961)—an
early forerunner of computer-assisted learning. His teaching machine tested students’ knowledge as
they worked through various school subjects. If students answered questions correctly, they received
immediate positive reinforcement and could continue; if they answered incorrectly, they did not receive
any reinforcement. The idea was that students would spend additional time studying the material to
increase their chance of being reinforced the next time (Skinner, 1961).