This paper addresses the formation of social norms of cooperation through interaction in repeated Public Goods Games, using novel multilevel techniques. Cooperation has traditionally been understood as the interplay of static factors such as shared social identity and pre-existing norms. This study investigates the dynamic emergence of cooperative norms in the presence or absence of social categorization. A small effect of categorization was found: Categorization helps initiate and maintain higher levels of cooperation. However, the differences in emergent cooperation between small groups were much stronger than the differences between the Categorization and Non-Categorization conditions. Using explorative analyses, three distinct classes of groups were found. Within groups, group members follow nearly identical rules for their choice of cooperative behavior. We argue that individual behavior converged because of the social interactions within these groups. Overall, the development of cooperation is best predicted by the process of norm formation that occurs when social identities emerge.

We investigated the effect of structural interdependencies between groups (especially inequality), and interdependencies between individuals on ingroup favoritism in minimal group situations. Previous research has attempted to determine whether ingroup favoritism is produced by categorization or intragroup interdependencies (reciprocation expectations), but recent literature suggests that it is not possible to tease these influences apart. We report two studies that investigate how ingroup favoritism evolves over time in social interaction. The levels of ingroup favoritism were affected by categorization and inequality, and the level of ingroup favoritism changed over time, increasing or decreasing depending on the nature of the initial intergroup structure. We conclude by providing two explanations for this change: emergent norms, and changes to the intergroup situation produced by interaction. Our experiments confirm the value of studying the evolution of minimal group behavior, especially for explaining why low status groups act to preserve intergroup inequalities.

This paper addresses the formation of social norms of cooperation through interaction in repeated Public Goods Games, using novel multilevel techniques. Cooperation has traditionally been understood as the interplay of static factors such as shared social identity and pre-existing norms. This study investigates the dynamic emergence of cooperative norms