Science moves through history along many routes and at many speeds. There are slow times, all too frequently, when it seems to stagnate, making little or no progress. Then there are those exciting, dynamic periods when new discoveries spark waves of dialog, attention, research, and progress. These discoveries quite literally change what we know about how the world works. The history of psychology is no different from the other sciences. There has been psychological research that has had remarkable and lasting effects on the various disciplines that comprise the science we call psychology. The findings generated from these studies have changed our knowledge of human behavior, and they have set the stage for countless subsequent projects and research programs. Even when the results of some of these pivotal studies have later been drawn into controversy and question, their effect and influence in a historical context never diminishes. They continue to be cited in new articles; they continue to be the topic of academic discussion; they continue to form the foundation for textbook chapters; and they continue to hold a special place in the minds of psychologists.
The concept for this book grew out of my many years of teaching psychology. Psychology textbooks are based on those key studies that have shaped the science of psychology over its relatively brief history. Textbooks, however, seldom give the original studies the attention they richly deserve. Usually the research processes are summarized and diluted to the point that little of the life and excitement of the discoveries remain. Sometimes the way the methods and findings are reported can even mislead the reader about the study's true impact and influence. This is in no way a criticism of the textbook writers who work under length constraints and must make many difficult choices as to what gets included and in how much detail. The situation is, however, unfortunate, since the foundation of all of psychology is research, and it is through a century of ingenious and elegant studies that our knowledge and understanding of human behavior have been expanded and refined to the level of sophistication that exists today.
This book is an attempt to fill the rather large gap between the psychology textbooks and the research that made them possible. It is a journey through the headline history of psychology. My hope is that the way the 40 chosen studies are presented will bring them back to life so that you can experience them for yourself. This book is intended for anyone who wishes a greater understanding of the true roots of psychology.
CHOOSING THE STUDIES
The studies included in this book were carefully chosen from those found in psychology texts and journals and from those suggested by leading authorities in psychology's many subfields. The number wasn't planned, but as the studies were selected, 40 seemed to be about right both from a historical point of view and in terms of length. The studies chosen are arguably the most famous, the most important, or the most influential in the history of psychology. I use the word arguably since many who read this book may wish to dispute some of the choices. One thing is sure: There is no single list of 40 studies that would satisfy everyone. However, the studies included here are the ones that continue to be cited most frequently, stirred up the most controversy when they were published, sparked the most subsequent related research, opened new fields of psychological exploration, or changed most dramatically our knowledge of human behavior. These studies are organized according to the subfield into which they best fit, including Biology and Human Behavior; Consciousness; Learning and Conditioning; Intelligence, Cognition, and Memory; Human Development; Emotion and Motivation; Personality; Psychopathology; Psychotherapy; and Social Psychology.
PRESENTING THE STUDIES
A basic format is used consistently throughout the book to promote a clear understanding of each study presented. Each chapter contains:
- An exact, readily available reference for where the original study can be found.
- A brief introduction summarizing the background in the field leading up to the study and the reasons the researcher carried out the project.
- The theoretical propositions or hypotheses on which the research rests.
- A detailed account of the experimental design and methods used to carry out the research, including, where appropriate, who the subjects were and how they were recruited; descriptions of any apparatus and materials used; and the actual procedures followed in carrying out the research.
- A summary of the results of the study in clear, understandable, nontechnical, nonstatistical, no jargon language.
- An interpretation of the meaning of the findings based on the author's own discussion in the original article.
- The significance of the study to the field of psychology.
- A brief discussion of supportive or contradictory follow-up research findings and subsequent questioning or criticism from others in the field.
- A sampling of recent applications and citations of the study in others' articles to demonstrate its continuing influence.
- References for additional and updated reading relating to the study.
Often, scientists speak in languages that are not easily understood (even by other scientists!). The primary goal of this book is to make these discoveries meaningful and accessible to the reader, to allow you to experience the excitement and drama of these remarkable and important discoveries. Where possible and appropriate, the studies presented here have been simplified and edited for ease of reading and understanding. However, this has been done in such a way that the meaning and elegance of the work is preserved and the impact of the research is distilled and clarified.
NEW TO THE FOURTH EDITION
This fourth edition of Forty Studies contains many significant and substantive changes and additions including two important new studies and updates in all of the "Recent Applications" sections near the end of each reading, reflecting the numerous citations of each of the 40 studies in articles from professional journals during the three years since the completion of the third edition (1998-2000). The findings of over 60 new studies from those three years are briefly summarized to allow you to experience the ongoing influence of these 40 studies that changed psychology. The new studies are fully referenced at the end of each chapter along with other relevant sources. As you read through them, you will be able to appreciate the breadth and richness of the contributions still being made by the 10 studies that comprise this book.
Over the three years since completing the third edition, I have enjoyed numerous conversations with and received helpful suggestions and counsel from colleagues in many psychology subfields about potential changes in the selection of studies for this new edition. Two research areas that have been expanding in their influence over the past 20 years or so have been central to many of my communications from the field, and, consequently, have been added to this book. Interestingly, both are at the core of opposite sides of the nature-nurture debate.
One of these is an article representing the recent (and current) swing of the philosophical pendulum from the broad focus on environmental influences that dominated psychology for most of the second half of the twentieth century, to a new recognition that inherited; genetic forces appear to play a much stronger role than anyone since Sigmund Freud has contemplated. A great deal of the evidence for this new biological focus has emanated from Drs. Thomas Bouchard and David Lykken's studies of twins at the Minnesota Center for Twin and Adoption Research at the University of Minnesota. An article from 1990, providing an early summary of their surprising findings has been selected for this edition and may be found in the opening section on the biology of human behavior.
The second new study included here is from an historically pivotal body of work by Professor Harry Triandis at the University of Chicago on the influence of culture on human behavior. His work has provided social scientists with a guiding framework in which to place our increasing sensitivity to, and recognition of, the fundamental role cultural forces play in the formation of personality and social behaviors. Triandis, over the past 30 years, has developed and refined his theory suggesting that most human societies fall within one of two basic categories: collectivist cultures and individualistic cultures. It appears that this single, yet complex, theoretical model explains a great deal about how the culture in which you are raised determines, in large measure, who you are. An article from 1988 in which Triandis defined his theory and demonstrated various aspect of the collectivist-individualistic dimension in a series of three studies, has been included in the personality section of the fourth edition.
THE ETHICS OF RESEARCH INVOLVING HUMAN OR ANIMAL SUBJECTS
Without subjects, scientific research is virtually impossible. In physics, the subjects are subatomic particles; in botany, they are plants; in chemistry, they are the elements of the periodic table; and in psychology, the subjects are people. At times, certain research procedures or behaviors under study do not permit the use of human subjects, so animal subjects are substituted. However, the goal of animal research is to better understand humans, not the animals themselves. In the following pages, you will be reading about research involving both human and animal subjects. Some of the studies may cause you to question the ethics of the researchers in regard to the procedures used with the subjects. Usually, when painful or stressful procedures are part of a study being discussed, the question of ethics will be noted in the chapter. However, since this is such a volatile and topical issue, a brief discussion of the ethical guidelines followed by present-day psychologists is included here in preparation for some of the studies described in this book.
Research with Human Subjects
The American Psychological Association (APA) has issued strict and clear guidelines that researchers must follow when carrying out experiments involving human participants. A portion of the introduction to those guidelines reads as follows:
Psychologists respect the dignity and worth of the individual and strive for
the preservation and protection of fundamental human rights. They are
committed to increasing knowledge of human behavior and of people's understanding
of themselves and others and to the utilization of such knowledge
for the promotion of human welfare. While pursuing these objectives,
they must make every effort to protect the welfare . . . of the research participants
that may be the object of study. from American Psychological Association.
(1981). Ethical principles of psychologists. American Psychologist, 36, 633-638
To adhere to those principles, researchers follow certain basic rules for all studies involving human subjects:
- Informed consent. A researcher must explain to potential subjects what the experiment is about and what procedures will be used so that the individual is able to make an informed decision whether to participate. If the person then agrees to participate, this is called informed consent. There are times, as you will see in this book, when the true purposes of an experiment cannot be revealed because this would alter the behavior of the subjects and contaminate the results. In such cases, when deception is used, a subject still must be given adequate information for informed consent and the portions of the experiment that are hidden must be justifiable based on the importance of the potential findings.
- Freedom to withdraw at any time. All human subjects in all research projects must know that they may withdraw freely from the experiment at any time. This may seem an unnecessary rule, since it would seem obvious that any subject who is too uncomfortable with the procedures can simply leave. However, this is not always so straightforward. For example, undergraduate students are often given course credit for participating as subjects in psychological experiments. They may feel that withdrawing will influence the credit they receive and they will not, therefore, feel free to do so. When subjects are paid to participate, if they are made to feel that their completion of the experiment is a requirement for payment, this could produce an unethical inducement to avoid withdrawing when they wish to do so. To avoid this problem, subjects should be given credit or paid at the beginning of the procedure just for showing up.
- Debriefing and protection from harm. Experimenters have the responsibility to protect their subjects from all physical and psychological harm that might be produced by the research procedures. Most psychological research involves methods that are completely harmless, both during and after the study. However, even seemingly harmless procedures can sometimes produce negative effects such as frustration, embarrassment, or concern. One common safeguard against those effects is the ethical requirement for debriefing. After subjects have completed an experiment, especially one involving any form of deception, they should be debriefed. During debriefing, the true purpose and goals of the experiment are explained to them and they are given the opportunity to ask any questions about their experiences. If there is any possibility of lingering aftereffects from the experiment, the researchers should provide subjects with their phone numbers for further discussion if necessary.
- Confidentiality. All results from subjects in experiments should be kept in complete confidence unless specific agreements have been made with the subjects. This does not mean that results cannot be reported and published, but this is done in such a way that individual data cannot be identified. Often, no identifying information is even acquired from subjects, and all data are combined to arrive at average differences among groups.
In research involving children, parental consent is required and the same ethical guidelines apply.
As you read through the studies included in this book, you may find a few studies that appear to have violated some of these ethical principles. These studies were carried out long before formal ethical guidelines existed and could not be replicated today. The lack of guidelines, however, does not excuse past researchers for abuses. Judgment of those investigators must now be made by each of us individually and we must learn, as psychologists have, from past mistakes.
Research with Animal Subjects
One of the hottest topics of discussion in and outside of the scientific community is the question of the ethics of animal research. Animal-rights groups are growing in number and are becoming increasingly vocal and militant. There is more controversy today over animal subjects than human subjects, probably because animals cannot be protected, as humans can, with informed consent, freedom to withdraw, or debriefing. Additionally, the most radical animal rights activists take the view that all living things are ordered in value by their ability to sense pain. In this conceptualization, animals are equal in value to humans and, therefore, any use of animals by humans is seen as unethical. This use includes eating a chicken, wearing leather, and owning pets (which according to some animal-rights activists is a form of slavery).
At one end of the spectrum, many people believe that research with animals is inhumane and unethical, and should be prohibited. However, nearly all scientists and most Americans believe that the limited and humane use of animals in scientific research is necessary and beneficial. Many lifesaving drugs and medical techniques have been developed through the use of animal experimental subjects. Animals have also often been subjects in psychological research to study issues such as depression, brain development, overcrowding, and learning processes. The primary reason animals are used in research is that to carry out similar research on humans would be clearly unethical. For example, suppose you wanted to study the effect on brain development and intelligence of raising infants in an enriched environment with many activities and toys vs. an impoverished environment with little to do. To assign human infants to these different conditions would simply not be possible. However, most people would agree that rats could be studied without major ethical concerns to reveal findings potentially important to humans (see the reading in this book on research such as this by Rosenzweig and Bennett).
The American Psychological Association, in addition to its guidelines on human subjects, has strict rules governing research with animal subjects designed to ensure humane treatment. These rules require that research animals receive proper housing, feeding, cleanliness, and health care. All unnecessary pain to the animal is prohibited. A portion of the APA's "Care and Use of Animals" reads as follows:
Psychologists make every effort to minimize discomfort, illness, and pain of
animals. A procedure subjecting animals to pain, stress, or privation is used
only when an alternative procedure is unavailable and the goal is justified by
its prospective scientific, educational, or applied value. from American Psychological
Association. (1981). Ethical principles of psychologists. American Psychologist,
In this book, there are several studies involving animal subjects. In addition to the ethical considerations of such research, there are also difficulties in generalizing from animal findings to humans. These issues are discussed within each chapter that includes animal research. Each individual, whether a researcher or a student of psychology, must make his or her own decisions about animal research in general and the justifiability of using animal subjects in any specific instance. If you allow that animal research is acceptable under some circumstances, then for each study involving animals in this book, you must decide if the value of the study's findings support the methods used.
One final note related to this issue involves a development in animal research that is a response to public concerns about potential mistreatment. The city of Cambridge, Massachusetts, one of the major research centers of the world with institutions such as Harvard University and MIT, created the position of Commissioner of Laboratory Animals within the Department of Health and Hospitals. This was the first such governmental position and is currently held by a veterinarian, Dr. Julie Medley. Cambridge is home to 22 research laboratories that house approximately 60,000 animals. The commissioner's charge is to ensure humane and proper treatment of all animal subjects in all aspects of the research process, from the animals' living quarters to the methods used in administering the research protocols. If a lab is found to be in violation of Cambridge's strict laws concerning the humane care of lab animals, the commissioner is authorized to impose fines of up to $300 per day (see People magazine, May 27, 1991, p. 71).
The studies you are about to experience in this book have benefited all of humankind in many ways and to varying degrees. The history of psychological research is a relatively short one, but it is filled with the richness and excitement of discovering human nature.
I would like to express my sincere gratitude to Charlyce Jones Owen, Editorial Director of the Humanities Division at Prentice Hall, for her commitment to and support of this project from the beginning, three editions ago. I am also very grateful to Jayme Heffler, Psychology Acquisitions Editor at Prentice Hall for her valuable support and assistance on this fourth edition. I must convey my appreciation as well to Bill Webber, former Prentice Hall executive editor, for our rewarding and productive association over many years. I once again extend many thanks to Nancy Marcus Land and Pam Blackmon at Publications Development Company of Texas for their insightful, accurate, and talented design, production, and copy editing of the fourth-edition manuscript. I extend my personal appreciation to Bruce Kenselaar for continuing to lend his considerable talents in designing the cover of this and past editions. My genuine appreciation goes out to my psychology colleagues in the field who have taken the time, interest, and effort to communicate to me their comments, suggestions, and wisdom relating to past editions of this book. I have attempted at every opportunity to incorporate their valued insights into the manuscript. Thanks also to the following reviewers whose thoughtful input helped guide my changes and additions in the fourth edition: Joshua R. Cooper, University of Vermont; Phil D. Warm, Missouri Western State College; Margaret P. Munger, Davidson College; and Robin L. Bowers, College of Charleston. Finally, to my students, friends, and colleagues at New England College in New Hampshire, Mendocino College in California, and at many other colleges and universities who have participated in the history of this book in many tangible and intangible ways over the past 12 years (you know who you are), I extend my best wishes and heartfelt thanks.
ROGER R. HOCK