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 of a shared reward, even if they wind up empty-handed. Chimps, it turns out, are not so picky and will (rationally, an economist might add) take whatever they can get, according to an October 2007 Science 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 one another—unless you consider who exactly 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.
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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 computers 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 the 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. —Lucas Laursen