American Scientist

An Argument for Mind. Jerome Kagan. xiv + 287 pp. Yale University Press, 2006. $27.50.

In an old New Yorker cartoon, one crotchety-looking guy in a lab coat says to another, "One thing I'll say for us, Meyer—we never stooped to popularizing science." The same can't be said of Jerome Kagan, emeritus professor of psychology at Harvard. Kagan is one of the most famous developmental psychologists in the world, and yet I have seen the mention of his name provoke eye rolling among some academics—probably because he is both a popularizer, with an enthusiasm that can seem showy, and a generalist, with research interests that range from the biological to the cultural ends of the spectrum. Such scornful scholars may be thinking that it is slightly unseemly to venture out of the lab into public view or that breadth of interest necessarily sacrifices depth of understanding.

Kagan's latest book, An Argument for Mind, mixes autobiography with a history of psychology over the past 50 years. He uses his own journey from the Ph.D. program in psychology at Yale to the Fels Research Institute and then to Harvard to illustrate the movement of the field from the behaviorism of the 1950s and its overemphasis on environmental causes of behavior to the current acknowledgment of the importance of biological influences. Kagan contributed to this movement from nurture toward nature with his research on temperament, or biologically based differences in infant personality. He takes the position that some children are naturally predisposed to be inhibited or exuberant, although these tendencies can be altered by experience. In other words, nature and nurture are important.

Kagan may be a victim of his own success, however, in that this conclusion, which would have been startling in the 1950s, seems unsurprising in 2006. Indeed, empirical evidence consistent with Kagan's claims about the biological bases of behavioral tendencies continues to come in, such as the recent finding by Gleb Shumyatsky and colleagues that removing a single gene associated with protein expression in the amygdala reduces fearful behavior in mice.

Kagan has never been one to shy away from controversy or the limelight. He picked a very public fight with attachment theorists, arguing that their procedures really measure a child's temperament more than the security of the emotional bond between child and parent. And in the late 1990s, when Judith Rich Harris burst onto the scene with her critiques of developmental psychology (most notably in her 1998 book The Nurture Assumption), Kagan took it upon himself to defend the field, denouncing her conclusions in unusually strong terms ("total nonsense," "crazy"). The two of them clashed in the online magazine Slate in 1998 and on an ABC News special in 1999. In the ABC News piece, Kagan implied that Harris, a textbook writer, is unqualified to interpret the research literature because she is not a researcher herself. Students to whom I have shown this video have commented that Kagan comes across as a snob. Kagan's ire toward Harris is somewhat surprising in that they are in many ways natural theoretical allies: On the nature-nurture issue, they both emphasize heredity and criticize attachment theory's emphasis on early experience. They differ, however, in their relative weighting of environmental influences, with Harris giving more weight to peers and less to parents.

Kagan says in An Argument for Mind that he does not enjoy the role of critic, but he certainly plays that part a lot. For example, he is critical of the selfishness, hedonism and materialism of modern Western culture. He also criticizes evolutionary biology's assumption that human behavior is primarily driven by maximizing reproductive success and inclusive fitness; he believes that we are instead more motivated by the desire to be virtuous—to meet our personal moral standards. And he also suggests that one cannot use evolutionary theory to explain the popularity of religion—yet both psychologist Jesse Bering and philosopher Daniel Dennett have recently done just that.

The book takes its title from a chapter in which Kagan rejects neuroscience's claim that understanding the mind will eventually be reduced to understanding the brain. He argues that psychological properties are emergent and not reducible to physical terms. His position is not new; similar arguments have been made by philosophers of mind such as Jerry Fodor and Thomas Nagel. However, Kagan provides an excellent summary of the evidence for the nonequivalence of physical and psychological states.

Kagan expounds repeatedly on his personal philosophy of science. Researchers should prefer hypotheses and categories suggested by open-minded observation over those derived from theoretical preconceptions, he argues. For example, Kagan believes that many current psychological terms, such as stress and fear, are too broad to be useful, because they lump together states with very different physical manifestations and psychological impacts, especially across cultures and species. He predicts that psychological descriptions in the future will be much more context-specific, even considering the season of year and time of day. He also discusses how the popularity of scientific theories depends on how well they mesh with the zeitgeist of the culture. For example, behaviorism's emphasis on nurture over nature resonated with American egalitarianism ("all men are created equal"), and Freud's psychoanalytic theory fits with American ambivalence about sexuality. Finally, Kagan argues that society should not expect science to settle ethical issues; science can provide information but cannot tell us what, if anything, to do with that information.

At 287 pages, the book is not long, but it is densely packed with ideas. Kagan illustrates his points with references that range from literary to neurological, although their relevance is not always obvious. His metaphors can be colorful and a little over the top. He has an interesting tendency to anthropomorphize nature, in particular as a feminine figure to be revealed:

The inability to know the future, a frustrating source of uncertainty in the life sciences, and especially in studies of human behavior, is the wall in the labyrinth that will not fall until history, signaling its vulnerability, allows our hero to pass into the next room to confront another barrier on the endless journey to the center, where truth, reclining on a silk couch, waits patiently to be touched.

I'm tempted to ask what truth is wearing.

Overall, Kagan comes across as optimistic—about human nature ("loyal, caring, and cooperative"), psychology's progress to date ("extraordinary") and even prejudice at Harvard ("essentially gone"). Therefore it is somewhat surprising that in his conclusion he issues a pessimistic forecast for the future of psychology as a unified field, predicting a split into neurobiological and sociocultural groups. Personally, I hope he is wrong, for I fear that such a division would result in fewer generalists and popularizers such as Kagan.