The mere presence of an outgroup member disrupts the brain's feedback-monitoring system.

Much of human learning happens in the social world. A person's social identity-the groups to which they belong, the people with whom they identify-is a powerful cue that can affect our goal-directed behaviors, often implicitly. In the present experiment, we explored the underlying neural mechanisms driving these processes, testing hypotheses derived from social identity theory. In a within-subjects design, participants underwent a minimal group manipulation where they were randomly assigned to an arbitrary ingroup. In two blocks of the experiment, participants were asked to complete a task for money while being observed by an ingroup member and outgroup member separately. Results revealed that being observed by an ingroup or outgroup member led to divergent patterns of neural activity associated with feedback monitoring, namely the feedback-related negativity (FRN). Receiving feedback in the presence of an ingroup member produced a typical FRN signal, but the FRN was dampened while receiving feedback in the presence of an outgroup member. Further, this differentiated neural pattern was exaggerated in people who reported greater intergroup bias. Together, the mere presence of a person can alter how the brain adaptively monitors feedback, impairing the reinforcement learning signal when the person observing is an outgroup member.