Chimps=Economists?

Katherine Mangu-Ward | October 9, 2007

Economists have long been bedeviled by the fact that people consistently refuse to behave as economic models predict. But now the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany, has moved on to more compliantly rational subjects: chimps.

They find that "unlike humans, chimpanzees conform to traditional economic models." When presented with a simplified version of the ultimatum game, in which one player decides how to divide a windfall between himself and another player, people frequently reject "unfair" offers (say, 8 for me, 2 for you). When an offer is rejected, both parties get nothing. Because if this human tendency, people tend to wind up with something close to a 50/50 split. But rejected small offers is not rational, and it infuriates economists when people consistently turn down small gains just to punish the other player for being unfair.

Unlike humans faced with these games, chimpanzee responders accepted any nonzero offer, whether it was unfair or not. The only offer that was reliably rejected was the 10/0 option (responder gets nothing). The researchers conclude that chimpanzees do not show a willingness to make fair offers and reject unfair ones. In this way, they behave like selfish economists rather than as social reciprocators.

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