Decoding fairness motivations from multivariate brainactivity patterns

A preference for fairness may originate from prosocial or strategic motivations: we may wish to improve others’ well-beingor avoid the repercussions of selfish behavior. Here, we used functional magnetic resonance imaging to identify neuralpatterns that dissociate these two motivations. Participantsplayed both the ultimatum and dictator game (UG–DG) asproposers. Because responders can reject the offer in the UG, butnot the DG, offers and neural patterns between the gamesshould differ for strategic players but not prosocial players. Using multivariate pattern analysis, we found that the decodingaccuracy of neural patterns associated with UG and DG decisionscorrelated significantly with differences in offers betweengames in regions associated with theory of mind (ToM), such as the temporoparietal junction, and cognitive control, such asthe dorsolateral prefrontal cortex and inferior frontal cortex. Weconclude that individual differences in prosocial behaviormay be driven by variations in the degree to which self-control and ToM processes are engaged during decision-makingsuch that the extent to which these processes are engaged is indicative of either selfish or prosocial motivations.