The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

How social is inequity aversion in humans? Like nonhuman primates, children reject inequity in a nonsocial game


1Human Evolutionary Biology, Harvard University, 2Program for Evolutionary Dynamics, Harvard University, 3Harvard College, Harvard University, 4Psychology, Harvard University

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Inequity aversion (IA), which is intolerance for uneven reward distributions, is an important component of the human sense of fairness. IA is normally assumed to occur only under social conditions and thus virtually no study of IA in humans has tested whether individuals reject unfair offers in nonsocial contexts. Studies of IA in nonhuman primates (hereafter primates), by contrast, test IA in both social and nonsocial contexts and evidence for IA hinges on the demonstration that subjects reject inequity more when they are paired with a social partner than when no partner is present. Indeed, some primate studies have shown that responses to inequity are strongest in social conditions. However, individuals in these studies also typically reject unequal offers in nonsocial conditions. Rejections in a nonsocial context suggest that primates react differently to inequity in comparison to humans. Here, we test this hypothesis by examining IA in children in a nonsocial game.

We tested 185 4-9 year old children in a nonsocial economic game where subjects could accept or reject equal and unequal offers of candy. Results show that 6-9 year old children reject inequity in this game. These results are compared to those from a social version of the game (Blake and McAuliffe, 2011), which shows that, like primates, individuals exhibit stronger IA in a social context.

More broadly, these results suggest that a simple mechanism whereby individuals gauge their payoffs relative to those available may be the evolutionary starting point for a more derived form of social IA.

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