A stranger in a strange land: Promises and identity

One's social identity tends to favor those belonging to one's group. At the same time, communication has had beneficial social consequences in controlled laboratory experiments. Can communication improve trust and outcomes between out-group members by making them more familiar? We construct a simple weak mechanism of group favoritism (different assigned colors) that induces in-group favoritism. Communication increases cooperation but does not affect per se the social identity gap, i.e., people make more favorable choices for in-group members. However, mutual promises are more effective for out-groups than in-groups, reducing or eliminating the social-identity gap. So perhaps, in some sense, out-group members are seen as more like in-group members when they have experienced mutual promises. We also find evidence that the two groups' decisions are driven by different motivations, one based on expectations in-groups and one based on moral commitment in the case of out-groups.