Harvard students and Amazon Indians help identify the brain's lie detector

A "cheating centre" in the brain has been identified by scientists with the help of Harvard students, a tribe of Amazonian Indians and a man who cannot handle money.

The findings suggest two million years of human evolution have led to a specialised set of brain cells devoted to the critically important social task of detecting whether someone is a cheat or a liar.

Discovering that the centre functions just as well in members of a remote Amazon tribe as in the minds of well-educated Harvard undergraduates demonstrated its basic role in human biology, the scientists said.

Two studies published yesterday in the Proceedings of the National Academy of Sciences have shown that cheat-detection is a universal feature of human nature and that it is performed quite separately from the other tasks of the brain. Anthropologists and evolutionary psychologists have long suspected that humans must be gifted in detecting cheats because of the importance of reciprocal cooperation in social behaviour.

"For social exchange to evolve in a species, individuals must be able to detect cheat-ers," say the researchers, led by Leda Cosmides and John Tooby, of the University of California at Santa Barbara.

The scientists studied a brain-damaged patient, known only by the initials RM, who was quite normal in all respects except that he was naive when it came to interacting with other people and had difficulty with money.

"RM's differential impairment indicates that being able to detect potential cheaters may be a separable component of the human mind," say the researchers. They suggest the cheating centre is in the limbic system of the brain.

A separate series of tests of Harvard undergraduates and the Shiwiar tribe found even people living the simplest existence were just as good at detecting cheating.