Technology & Science

Chimps show sense of 'fair play'

Chimpanzees show a similar sense of fairness to humans, a study suggests.

Chimpanzees show a sense of fairness similar to that in humans – one that changes depending on their social bonds with other animals, a study suggests.

It's the first time that nonhuman primates have been shown to react to inequity like humans, says the paper published Wednesday in the online edition of the Proceedings of the Royal Academy of Sciences.

Combined with the authors' previous study on fairness among capuchin monkeys, it suggests the sense of fair play may have a long evolutionary history in primates.

Primatologists at the Yerkes National Primate Centre in Atlanta, Sarah Brosnan and Frans de Waal, paired up chimpanzees and gave them each a piece of plastic.

When the chimps handed them back, the researchers doled out unequal rewards. They gave one animal a cucumber slice or celery stick and the other chimp a much more popular treat – a grape.

If a chimp had known its partner for less than eight years and got shortchanged, it would refuse to co-operate with the researchers.

If it had known the other animal for its entire life, however, it was much less likely to get upset.

The reaction parallels that seen among humans, who might become miffed when a stranger or enemy gets an unfair reward, but not when a family member or friend benefits.

"Human decisions tend to be emotional and vary depending on the other people involved," writes Brosnan, of Emory University.

"Our finding in chimpanzees implies this variability in response is adaptive and emphasizes there is not one best response for any given situation, but rather it depends on the social environment at the time."

The researchers received support from the National Science Foundation Graduate Research Fellowship and a National Institutes of Health Grant.