Later, over tapas at a chic Spanish restaurant in Old City, Kurzban uses the objects at hand to explain how evolutionary psychologists work.

“If you want to claim that something is an adaptation, that something is designed to serve a particular function,” he says, “then you need to show evidence of special design.” He pauses between bites of elegantly sauced morsels of chicken to ruminate on his utensils.

“If I wanted to say that this is a knife, whose function is cutting, it would be very nice to be able to show that it had a sharp edge and it had a handle, it had a certain heft.” He turns it over to demonstrate the point, then draws out the analogy: “If I could only look at this obliquely, which is what happens in psychology, then I might have to do some wriggling to see whether or not the blade is really sharp. And I might have to put it through lots of different tests. And that’s what we do in the laboratory.”

Kurzban has focused mostly on human “sociality,” as opposed to mating, which preoccupies many evolutionary psychologists. “Really what I think about is, ‘What are the human adaptations designed for social interaction?’” he says.

Cosmides particularly values Kurzban’s work on coalitional psychology and the psychology of collective action. Using the techniques of experimental economics, Kurzban has described how “people regulate their levels of cooperation when there is a public good,” she says. Specifically, he has shown that in a situation where people are not allowed to punish “free-riders” (those who don’t do their share), people “ratchet down” their contributions, causing “the whole operation to unwind.”

Such work, though not politically motivated, has obvious political implications, Cosmides says. She notes how disastrous collectivized agriculture proved in the old Soviet Union. “I think Rob’s work shows why.”

Kurzban’s most-cited contribution is a 2001 theory paper on stigma, co-authored with Wake Forest University’s Mark R. Leary. He explains: “That paper essentially says: ‘This category that social psychologists have been using—it’s not one thing, it’s multiple things, and those different things can be understood in the context of different adaptive problems and different adaptive mechanisms to try and solve them.’” Stigma is useful, Kurzban says, to avoid disease, “bad social exchange partners” (for instance, people who are unpredictable, dishonest, or poor), and “bad coalition partners.”

Daphne B. Bugental, professor of social and developmental psychology at the University of California at Santa Barbara, says that previous researchers have concentrated on “what stigma is, how it operates, and who is affected,” while “Kurzban’s approach addresses the basic why question.” Because he suggests that people sometimes avoid people with physical disabilities because they are responding to “ancient markers of risk” that may no longer be relevant, she says, his research could help combat prejudice. So, too, she says, could his “ground-breaking” work on race.

In “Can race be erased? Coalitional computation and social categorization,” co-authored with Tooby and Cosmides in 2001, Kurzban reports an experiment that showed that when race doesn’t correspond with alliances, “subjects markedly reduce the extent to which they categorize others by race, and indeed may cease doing so entirely.” That research is a good example of how the evolutionary paradigm can generate testable hypotheses. “Humans would not have been evolving in a world where there were different races around, although there would have been people of different ages and sexes. So race should be very different from age and sex,” says Kurzban. “The claim in the literature was that categorizing people by race was done automatically. And that paper shows it’s not automatic.”

Because of their essentialist leanings, evolutionary psychologists are sometimes accused of being “right-wing fascists,” in Kurzban’s phrase. But the race paper provoked e-mails charging that he was “pandering to left-wing liberals.” As a scientist, he shrugs off such reactions: “All I know is: Here are the data. If people have some political agenda they want to use it for, that’s actually not my business—or my problem.”

One of Kurzban’s current projects—an ambitious theory paper being considered for publication in the prestigious Personality and Social Psychology Review—also appears destined to provoke controversy. Titled “Modularity and the Social Mind: Are Psychologists Too Self-ish?,” it challenges the idea of the unitary “self,” as well as the importance of the notion of self-esteem. Attempting to explain why people often can’t enunciate a rationale for their own decisions, Kurzban and co-author C. Athena Aktipis, a doctoral student
at Penn, posit that different parts of the mind have different functions that aren’t always transparent to one another. “People aren’t going to like it,” Kurzban says, “but hopefully it will get a discussion going.”

Another paper, accepted by the journal Evolution and Human Behavior, takes a look at moralistic punishment. In two experiments, Kurzban found that if punishing cheaters by docking their pay entails an economic cost to the punisher, people are more likely to impose punishments when they are being observed. “Let me make an important distinction: People like wrongdoers to be punished,” he says. But “once an individual has to bear the cost of inflicting this punishment [him- or herself], they don’t actually seem all that willing” to do it. (“I think that’s exactly why we have things like a justice system,” he adds.)

“The argument,” he continues, “is [that] where you do see some punishment is when you get a reputational benefit from it. So we think that the story here might be one in which moralistic punishment is a signaling act,” meaning that it indicates something positive about the punisher. But, he says, “I wouldn’t take that one to the bank right now.” Another piece of the puzzle is gradually being filled in: Data collected by Kurzban’s students show that “people who punish a moderate amount are construed more favorably than people who don’t punish at all.”

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©2006 The Pennsylvania Gazette
Last modified 06/28/06

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FEATURE: The Reverse Engineer
By Julia M. Klein

“Really what I think
about is, ‘What are the
human adaptations
designed for social interaction?’”