Chimps Have a Sense of Fairness

Humans aren’t the only ones who cry “no fair.” In a classic test of fairness called the ultimatum game, apes will dole out an equitable share of their bananas — and when they don’t, their partners will complain, a new study shows.

The findings, published today (Jan. 14) in the Proceedings of the National Academy of Sciences, suggests that humans and chimpanzees may share an evolved sense of fairness common to many cooperative species, said lead study author Darby Proctor, a primatologist at Emory University.

“If you’re involved in some cooperative act you need to be sure you’re engaging in something that’s beneficial to you,” Proctor told LiveScience. “Comparing your rewards with others’ seems like it would be really, really important.”

Fair and square

In a classic economic trial called the ultimatum game, people are given $100 and can give some fraction of it to an anonymous partner they’ll never see again. The recipients can reject the offer if they don’t like it, in which case both people get nothing.

Rationally, the “smart” response would be to take any offer, no matter how low, but participants routinely reject offers lower than $10 or $20, said Manfred Milinski, an evolutionary biologist at the Max Planck Institute for Evolutionary Biology in Germany, who was not involved in the study. Most people offer around $40 to their partners and in some countries, people offer more than half of the money to partners, Milinski told LiveScience.

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