Group Membership, Team Preferences, and Expectations (This is a new version of CEEL WP 6-09)

Group membership increases cooperation in social dilemma games, altruistic donation in dictator games, and fair offers in ultimatum games. While the empirical study of group action has grown rapidly over the years, there is little agreement at the theoretical level on exactly why and how group membership changes individual behaviour. According to some theorists, the effect of group framing is channelled primarily via the beliefs of group members, while others identify changes in preference as the key explanatory mechanism. We report an experiment using the minimal group paradigm and a prisoner’s dilemma with multiple actions, in which we manipulate players’ beliefs and show that common knowledge of group affiliation is necessary for group action. We also observe puzzling variations in behaviour when knowledge of group membership is asymmetric, which may be interpreted as cognitive dissonance generated by a normative cue administered in a highly unusual situation.