The ties that bind: Group membership shapes the neural correlates of in-group favoritism.

Across species, including non-human primates, rodents, and humans, prosocial behavior, the act of helping others, is preferentially provided to members of one's own group. Whereas a particularly ubiquitous example of this is kinship, whereby humans and animals expend greater resources and take more risks for their own kin, in-group prosocial behavior has been demonstrated among diverse shared social groups, including race and culture. In the current study, we made group membership salient by recruiting Chinese and American participants to engage in a prosocial decision-making task during fMRI with an American and Chinese confederate. We found across all participants that donations to the in-group relative to out-group was associated with increased activation in the ventral striatum. Moreover, participants with a greater sense of group identity and Chinese participants relative to American participants, showed heightened activation in self-control (VLPFC, ACC) and mentalizing (TPJ, DMPFC) regions when contributing to the out-group relative to in-group. Our findings provide novel evidence about the neural mechanisms involved in intergroup prosocial behavior.