Individual Heterogeneity in Punishment and Reward

We design experiments to study the extent to which individuals differ in their motivations behind costly punishment and rewarding. Our findings qualify existing evidence and suggest that the largest fraction of players is motivated by a mixture of both inequity-aversion and reciprocity, while smaller fractions are primarily motivated by pure inequity-aversion and pure reciprocity. These findings provide new insights into the literature on other-regarding preferences and may help to reconcile important phenomena reported in the experimental literature on punishment and reward.