An evolutionary approach to human intelligence leads to the radically different—and highly counterintuitive—view that our cognitive architecture includes evolved reasoning programs that were specialized by selection for distinct adaptive problems, such as social exchange and evading hazards. Although such a view strikes many as implausible in the extreme—why would anything in the mind be so strangely specialized?—the careful analysis of adaptive problems allows the derivation of rich sets of testable and unique predictions about our cognitive architecture. When these predictions are empirically tested—as here—the results typically support the view that the human cognitive architecture contains specializations for adaptive problems our ancestors faced. In this case, we can show that the cheater detection system functions with pinpoint accuracy, remaining inactive not only on rules outside the domain of social exchange but also on social exchanges that show little promise of revealing a cheater. In the contest of intuition versus evidence, it will be interesting to see which will prove the more persuasive. Human intelligence, like the sediments of east Africa, may preserve powerful signals from the evolutionary past. And, maybe, the Earth really does orbit the sun.

The authors thank Roger N. Shepard, the National Institutes of Health Directors’ Pioneer Award to L.C., the National Science Foundation Young Investigator Award to J.T., the James S. McDonnell Foundation, and a UCSB Academic Senate grant.