Little is known about the neurobiological mechanisms underlying prosocial decisions and how they are modulated by social factors such as perceived group membership. The present study investigates the neural processes preceding the willingness to engage in costly helping toward ingroup and outgroup members. Soccer fans witnessed a fan of their favorite team (ingroup member) or of a rival team (outgroup member) experience pain. They were subsequently able to choose to help the other by enduring physical pain themselves to reduce the other's pain. Helping the ingroup member was best predicted by anterior insula activation when seeing him suffer and by associated self-reports of empathic concern. In contrast, not helping the outgroup member was best predicted by nucleus accumbens activation and the degree of negative evaluation of the other. We conclude that empathy-related insula activation can motivate costly helping, whereas an antagonistic signal in nucleus accumbens reduces the propensity to help.

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The superior temporal sulcus (STS) is the chameleon of the human brain. Several research areas claim the STS as the host brain region for their particular behavior of interest. Some see it as one of the core structures for theory of mind. For others, it is the main region for audiovisual integration. It plays an important role in biological motion perception, but is also claimed to be essential for speech processing and processing of faces. We review the foci of activations in the STS from multiple functional magnetic resonance imaging studies, focusing on theory of mind, audiovisual integration, motion processing, speech processing, and face processing. The results indicate a differentiation of the STS region in an anterior portion, mainly involved in speech processing, and a posterior portion recruited by cognitive demands of all these different research areas. The latter finding argues against a strict functional subdivision of the STS. In line with anatomical evidence from tracer studies, we propose that the function of the STS varies depending on the nature of network coactivations with different regions in the frontal cortex and medial-temporal lobe. This view is more in keeping with the notion that the same brain region can support different cognitive operations depending on task-dependent network connections, emphasizing the role of network connectivity analysis in neuroimaging.