Musical Chairs

Abstract

Participants played four rounds of a social card game in which they formed groups to make card hands and earn money. When isolates—players left out when groups formed—earned nothing, self-organized groups frequently included these extra people, even though this decreased earnings for group members. Although group composition remained fluid, with time most populations settled into a pattern of including everyone. When isolates received a small welfare payment, group formation was less ordered and predictable and exclusion remained common. Although exact repeats of the same group membership were relatively rare in both conditions, group stability was associated with more cooperative behavior by members. When membership was unstable, members were more likely to make excessive claims on group earnings, increasing their individual payoff at the expense of fellow group members.