Young Children Police Group Members at Personal Cost

Humans’ evolutionary success has depended in part on their willingness to punish, at personal cost, bad actors who have not harmed them directly—a behavior known as costly third party punishment. Though this behavior has been widely observed in adults, important questions remain as to its underlying psychology. We approached these questions from a developmental perspective, using a novel, naturalistic experiment to study costly punishment in young children (age 3-6). Results showed that even the youngest children in our sample (age 3-4) enacted costly punishment. In addition, younger (age 3-4) children policed members of their own group when placed in a position of authority. These effects of group membership and authority, along with evidence of the emergence of costly punishment at an age prior to the development of reputational concerns, indicate that costly punishment is promoted in part by the desire to regulate the behavior of potential cooperative partners, not just by spite or reputation management. Overall, the results shed new light on a behavior critical for cooperation, with implications for theories of human development, altruism, and justice.