Cooperation and crossed categorization in a minimal group context: testing the bounded generalized reciprocity and social identity accounts

Individuals display the tendency to cooperate more with in-group members than they do with out-group members (i.e. in-group favoritism) across diverse contexts. While previous studies have thoroughly investigated in-group favoritism when a single social category is salient, they have understudied how individuals cooperate with others when multiple social categories are simultaneously salient. To bridge this gap, we conducted a study to examine cooperation under crossed categorization, in which two dichotomous social categories are orthogonally crossed. We then examined the psychological mechanisms potentially underlying intergroup cooperation, including reputational concern, expected cooperation, and social identification, drawn from the theoretical perspectives of bounded generalized reciprocity and social identity theory. Overall, we found that two in-group memberships additively increased cooperation. That is, cooperation with a double in-group member (a person with two in-group memberships) was higher than that with a partial in-group member (i.e. a person with one in-group membership and one out-group membership). We also found that cooperation with a partial in-group member was larger than that with a double out-group member (a person with two out-group memberships). In addition, we found some evidence that expected cooperation partially mediated the relationship between in-group membership and cooperation.