Psychology: An Evolutionary Approach

Preface "Is it not reasonable to anticipate that our understanding of the human mind
would be aided greatly by knowing the purpose for which it was designed?"
(Williams 1966, p. 16).

In one important way this book is very different from other introductory psychology texts. Traditional psychology largely ignores the question of what the mind is for. This oversight puts traditional psychology seriously out of step with the rest of the life sciences, where design-for-a-function is recognized as the normal result of evolution by natural selection. The reader may hesitate but there's little room for doubt: Psychology is a life science. It studies the behavior of living things, not rocks or stars or electrons. The theory of evolution has inspired countless thousands of discoveries throughout the life sciences—in physiology, ecology, medicine, and the like. It's time to consider what this theory can offer to psychology.

In a sentence, natural selection shapes organisms by preserving those chance genetic variants that aid survival and reproduction. Contemporary biologists are convinced that every single species, including our own, owes its present form to a long history of natural selection. And their conclusion applies with equal force to every organ system; the mind and the behaviors it fosters are in no way exempt from this process. Thus our working assumption is that human psychology was designed by evolution, over millions of years, to solve the various challenges that faced our ancestors in their struggles to survive and reproduce.

We have chosen to write an introductory textbook for one simple reason. Evolutionary psychology is not a specialized subfield of psychology, such as personality psychology or abnormal psychology. Instead, it is a different way of thinking about the entire field. Its insights and methods should be the groundwork for the study of psychology, not an afterthought. Our goal is that, after reading this text, students will be able to think like evolutionists, not only about human behavior but also about a wide range of related matters.

But what of traditional psychology? Let us be clear. Traditional psychology it is a rich and vital field. But we have two general criticisms of it. First, because traditional psychology has no overarching theory of what we call "mind design," it can only take a trial-and-error approach to discovering the mind's operating principles. Unfortunately, trial and error is slow and inefficient, and it has led to some spectacular blind alleys, such as Freudian theory. Second, most of traditional psychology's reliable findings, about perception, thought, learning, motivation, social behavior and the like are more sensible and more informative when they are interpreted in an evolutionary framework. For example, long-standing debates such as the one over nature versus nurture, are illuminated and usefully resolved by evolutionary thinking.

Thus we begin in Chapter 1 by mapping the differences between evolutionary psychology and the more traditional non-evolutionary approach. Evolutionary psychologists and traditional psychologists often differ in how they develop their theories, in the kinds of questions they pose, and in the sorts of statements they accept as valid answers. There is an old saying that you can't understand what a person is saying unless you know who he's arguing against. Let's be explicit then; in a real sense we are arguing against many of the assumptions and interpretations (but few of the findings) of traditional psychology.

Studying psychology from an evolutionary viewpoint requires a clear understanding of the theory of evolution. Thus, one of our key missions is to explain what evolution is (and isn't), and what it can (and can not) do. These matters are the focus of Chapters 2, 3 and 4. There may be a temptation on the part of both students and professors to skip or deal briefly with these chapters in order to get on to the "meat" of the course—psychology. We beg you not to yield to the temptation! Every high-school graduate "knows what evolution is." But most harbor serious misconceptions: Evolution always fosters what is good for the species; because of their basis in genes, evolved traits are fixed and unresponsive to experience; species can usefully be arranged on a ladder from lower to higher. Wrong; wrong; and wrong again! According to a large majority of modern evolutionists all three of these ideas are dangerously off the mark. And there are many other pitfalls and misconceptions that must be discussed before evolutionary theory can be productively applied, to the study of psychology or to any other set of questions. Thus, a thorough grasp of the basics of modern evolutionary theory, especially as it relates to behavior, is essential to a full appreciation of the argument and evidence in this book.

The remaining chapters, 5 through 16, each treat one of the central topics of modern psychology. The topics include sensation and perception, development, learning, cognition, social psychology, abnormal psychology, motivation, individual differences and several others. In each of these chapters, our focus is not on reviewing the entire literature, either from a traditional or an evolutionary perspective. Instead, by discussing eight or ten examples in each chapter, we try to show what evolutionary psychology is, how it reorients the study of mind and behavior and how genuinely novel its conclusions can be. Our goal in exemplifying the evolutionary approach over such a wide range of topics is two-fold. Of course we intend that each reader will take away a richer understanding of human behavior and the psychological mechanisms that underlie it. But we also hope to demonstrate the considerable power of Darwin's theory. For any question about living things—from the sensory abilities of moths to the complexities of human cognition—an approach that neglects evolution is unlikely to produce full and satisfying answers. Charles Darwin explained the fundamental logic at the core of all living things. If we wish to understand our own, our friends', our mates' or our children's behavior, we'd be foolish to ignore the insights afforded by an evolutionary perspective.

As will be obvious from our citations and bibliography, we are not the first to imagine the outlines of an evolutionary psychology. Many students of human behavior, not only from the field of psychology, but also from biology, anthropology, economics and the other social sciences have contributed to the emergence of this field. Our primary debt, then, is to these colleagues, who had both the vision to foresee a synthesis between the evolutionary and behavioral sciences, and the interdisciplinary knowledge to build it. We hope that we have portrayed your pioneering efforts as clearly as you would have, and that many others will be encouraged to follow you down the Darwinian path.

In particular we thank our colleagues, Liz Cashdan, Martin Daly, Denys deCatanzaro, Jack Demarest, Jennifer Higa-King, L. Scott Johnson, Bruce MacDonald, Janet Mann, B. Kent Parker, Kathleen Ross, Kenneth Wildman, David Sloan Wilson, Matthew Window, and Thomas Zentall who offered frank, thorough and genuinely useful criticisms of parts, or in some cases all, of the book manuscript. You were (nearly) always right, and we have done our best to implement the various improvements you suggested while keeping in mind the kind of book we wanted to produce.

Indispensable editorial and organizational advice and support was generously provided by Cynthia and Claire Gaulin, Deborah Fenster, Frances Russello, Sharon Cosgrove, and especially our editor, Bill Webber. Bruce Hobart, our production supervisor, was the model of organization and good humor. We thank you all; it was a pleasure working with you.

Steven J.C. Gaulin
Donald H. McBurney

This theory, long the cornerstone of biology, is now beginning to reshape the social and human sciences. Just as selection has sculpted hearts, lungs and livers for specific functions, the human mind too can best be understood in the light of what it was designed to do. This text is the first to show the relevance of evolutionary thinking to the entire range of psychological phenomena, and it does so at a level appropriate for introductory students.

Drawing on their considerable interdisciplinary expertise, Gaulin and McBurney first lay out the fundamentals of modern evolutionary theory. Then they systematically apply this theory to questions from every domain of psychology: learning, cognition, perception, emotion, development, pathology, and more.

This approach has three significant benefits; It forms a bridge that joins psychology with the rest of the life sciences; it provides a powerful and easily mastered basis for hypothesis generation; and it offers an explanatory framework that, for the first time, unites all of psychology. The result is a text that is exciting for both student and professor.