Social Exchange : The Evolutionary Design of a Neurocognitive System

faced in the past, it reliably develops in all normal human gs, it develops without any conscious effort and in the absence explicit instruction, it is applied without any conscious aware-of its underlying logic, and it is functionally and neurally dis-from more general abilities to process information or behave igently erything should bc madc as simple as possible, but no simpler. By exchanging benefits-goods, services, acts of help and kindness-people can make themselves better off than they were before. This very basic fact of human social life is easy to take for granted. But when placed in zoological perspective , social exchange stands out as a strange phenomenon whose existence requires explanation. ZOOLOGICAL DISTRIBUTION Despite widespread investigation , social exchange (reciprocity, reciprocal altruism) has been reported in only a tiny handful of species, such as chimpanzees , baboons, lions, and vampire bats (see Dugatkin, 1997, and Hauser, in press, for contrasting views on the animal findings). Most species do not engage in this very useful form of mutual help. In contrast, social exchange is a characteristic of our species as language or tool use. Not only is social exchange found in every documented culture, but it is a feature of virtually every human life within each culture, taking on a mul-tiplicity of forms, such as returning favors, sharing food, reciprocal $t giving, market exchange, and extending acts of help with the (implicit) expectation that they will be re-Paleoanthropological evidence suggests that certain forms of social exchange were present in horninids at least two million years ago (Isaac, 1978), and its presence in other primates suggests it may be even more ancient than that. The fact that social exchange is an ancient and pervasive feature of human social life, yet rare in other species, is informative. It means that the neurocognitive macfiinery necessary for social exchange exists in humans, but not in most animals. But what, exactly, is the nature of the neurocogni-tive machinery that enables exchange, and how specialized is it for this function? Is social exchange a by-product of neural circuitry that causes one to reason logically? To think intelligently? To reason about all conditional rules? To reason about deontic rules-moral rules involving obligation and entitlement? O r does the ability to engage in social exchange require evolved mechanisms that were tailored by natural selection specifically for social exchange? The research discussed in this chapter explores a simple hypothesis: …