Social Discounting of Monetary Rewards: The Effects of Amount and Social Relationship

The purpose of the study was to test hypotheses regarding a form of social discounting in which the subjective value of a reward decreases as a function of the number of people it is shared with. Based on evolutionary theory, individuals' social discounting rates were expected to depend on both reward amount and the type of relationship with the people with whom the reward would be shared. As predicted, smaller amounts were discounted less steeply than larger ones, and social discounting was steepest when sharing with strangers and shallowest when sharing with family. The effect of the type of social relationship is consistent with Hamilton's inclusive fitness theory. The shallower discounting of smaller rewards may be adaptive when resources are limited; alternatively, this finding may be due to the degree of disappointment that is anticipated if the reward is unfairly shared, assuming that the disappointment increases with the size of the reward being withheld by the group.