The role of affiliation in the development of collaborative partner choice.

Collaboration is an early emerging component of successful cooperative relations that produces a cascade of positive social preferences between collaborators. Concurrently, robust preferences for affiliated others may restrict these benefits to in-group peers. We investigated how in-group affiliation (based on minimal group markers) and interpersonal affiliation (based on shared preferences) influence children's collaborative partner choice. We asked whether children prefer to collaborate with affiliated peers and if highlighting interpersonal affiliation with out-group members reduce in-group bias in partner choice. In Study 1, we assigned children (4-9 years,