Friend versus foe: Neural networks of prosocial decision-making with peers

Adolescents spend the majority of their time with their peer. Peers, and friends in particular, are known to
play a salient role in adolescents' social decisions. Adolescents can act in more prosocial or selfish ways
depending on who their interaction partner is. In the current study we aimed to examine prosocial behavior
and its neural correlates in interactions with peers. Participants (N = 50, Mean age = 14 years) took part in a
functional magnetic resonance imaging study where they were asked to make decisions regarding
distributions of coins in three economic exchange paradigms. Participants made decisions for four different
groups of peers: liked (i.e., friends), disliked classmates, neutral classmates, and unfamiliar peers. In line with
expectations, participants were more prosocial towards friends and more selfish towards disliked peers than
towards neutral and unfamiliar peers. Decisions for friends were associated with heightened activation in the
ventromedial prefrontal cortex (vmPFC) and temporoparietal junction (TPJ); prosocial decisions for friends
were specifically associated with heightened activation in putamen and the superior temporal sulcus (STS).
These findings suggest that, possibly, mentalizing processes and value estimations of the relationship might
underlie decisions involving friends. Decisions for disliked peers did not show significant heightened brain
activation. These findings will open pathways to better understand the underlying processes of prosocial
behavior in adolescence.