Neural precursors of future liking and reciprocity

Why do certain group members end up especially liking each other more than others? The prediction of interpersonal attraction has been a longstanding pursuit in the social sciences. We combine functional MRI and longitudinal social network data to test whether newly acquainted group members’ reward-related neural responses to one another predict their future attractions after completing a summer program together. We find that one’s own (actor’s) future liking of a particular group member (partner) is predicted jointly by actor’s neural valuation of partner and by that partner’s neural valuation of actor. These actor and partner effects exhibited equivalent predictive strength and were robust to each other, both individuals’ initial liking, and other potential drivers of tie formation. Behavioral findings indicated that actor’s relational attraction (to partner) and partner’s relational attraction (to actor) were initially independent (unreciprocated) at T1 yet became predominantly interdependent (reciprocated) by T2. This emergence of dyadic reciprocity was partly explained by the reciprocal pathways linking dyad members’ T1 neural data both to their own and to each other’s T2 liking outcomes. In sum, these findings elucidate interpersonal brain mechanisms that define how we ultimately end up liking (and being liked by) particular interaction partners, how group members’ initially idiosyncratic attractions become mutually reciprocated, and more broadly, how dyads evolve from the bonding of individuals. This study advances a flexible framework for researching the neural foundations of interpersonal sentiments and social relations that—conceptually, methodologically, and statistically—emphasizes group members’ relational interdependence.