Life may not be fair, but humans have a strong bias for fairness. In experiments humans will generally reject or punish a partner who offers noticeably less than half a shared reward, even if they wind up empty-handed. Chimps, it turns out, are not so picky and will (rationally, an economist might point out) take whatever they can get, according to an October 2007Science paper. So what could explain this difference between our closest living relatives and us?
The answer may lie in the social relationships that influence so many of our actions. Recent studies of primate fairness seem to contradict each other–unless you consider exactly who is cheating whom.
In 2003 a provocative study led by Sarah F. Brosnan, now at Georgia State University, concluded that capuchin monkeys were exhibiting humanlike social indignation when they turned down unfair deals. The monkeys refused to perform tasks if they saw companions getting better rewards for the same work. They threw tantrums, and their food rewards, to protest the unequal treatment.
In 2006, however, a group at American University reported the opposite result–their capuchins’ behavior was not affected by the food their partners got. In response, Brosnan’s group released an updated study, again showing the capuchins’ penchant for fairness. But some experts are still not convinced–Clive Wynne of the University of Florida warns that the different study designs make comparisons “messy.”
Brosnan argues that social relationships are more important than the other groups are accounting for. Her group found that chimpanzees were more likely to accept unfair deals from members of their social group than from outsiders. In another study, humans accepted unfair deals from a computer but not from people. These results imply that relationships matter when primates judge fairness, Brosnan says, and “may explain the failure to find a response in the [Science] study.” The chimps, in other words, may have been willing to accept unfair offers because they came from old pals.
Studying animal fairness could ultimately help us understand human cooperation and justice–but the jury is still out.