Human groups maintain a high level of sociality despite a low level of relatedness among group members. The behavioral basis of this sociality remains in doubt. This paper reviews the evidence for an empirically identifiable form of prosocial behavior in humans, which we call "strong...

Policies and explicit private incentives designed for self-regarding individuals sometimes are less effective or even counterproductive when they diminish altruism, ethical norms and other social preferences. Evidence from 51 experimental studies indicates that this crowding out effect is...