Trust in reciprocity (TR) is defined as the risky decision to invest valued resources in another party with the hope of mutual benefit. Several fMRI studies have investigated the neural correlates of TR in one‐shot and multiround versions of the investment game (IG). However, an overall characterization of the underlying neural networks remains elusive. Here, a coordinate‐based meta‐analysis was employed (activation likelihood estimation method, 30 articles) to investigate consistent brain activations in each of the IG stages (i.e., the trust, reciprocity and feedback stage). Results showed consistent activations in the anterior insula (AI) during trust decisions in the one‐shot IG and decisions to reciprocate in the multiround IG, likely related to representations of aversive feelings. Moreover, decisions to reciprocate also consistently engaged the intraparietal sulcus, probably involved in evaluations of the reciprocity options. On the contrary, trust decisions in the multiround IG consistently activated the ventral striatum, likely associated with reward prediction error signals. Finally, the dorsal striatum was found consistently recruited during the feedback stage of the multiround IG, likely related to reinforcement learning. In conclusion, our results indicate different neural networks underlying trust, reciprocity, and feedback learning. These findings suggest that although decisions to trust and reciprocate may elicit aversive feelings likely evoked by the uncertainty about the decision outcomes and the pressing requirements of social standards, multiple interactions allow people to build interpersonal trust for cooperation via a learning mechanism by which they arguably learn to distinguish trustworthy from untrustworthy partners. Hum Brain Mapp 38:1233–1248, 2017.

Loneliness is a central predictor of depression and major factor of all-cause mortality. Loneliness is supposed to be a warning signal prompting individuals to seek out social connections. However, lonely individuals seem to be less likely to engage in prosocial activities and are overall more socially withdrawn. Hence, it is yet unclear whether and how loneliness affects an individual’s social motivations. Prosocial attitudes and expectations about social interactions of lonely individuals might shed light on whether lonely individuals are more prone to connect or withdraw from social activities. Here, results from a large dataset (~ 15,500 individuals) provide evidence for both. In particular, lonely individuals indicate stronger altruistic attitudes, suggesting a positive tendency to build and maintain social bonds. However, they also report more negative expectations about others, as they believe their social partners be less fair and trustworthy, suggesting less favorable evaluations of social interactions. By highlighting an important link between loneliness, prosocial attitudes and social expectations, this work stresses the role of loneliness in social motivations, points to potential consequences for social behaviors, and proposes a mechanism for the paradoxical effects of loneliness on an individual’s social attitudes and expectations, with important implications for future basic and clinical research, as well as education, economics and public policy.

Theoretical accounts propose honesty as a central determinant of trustworthiness impressions and trusting behavior. However, behavioral and neural evidence on the relationships between honesty and trust is missing. Here, combining a novel paradigm that successfully induces trustworthiness impressions with functional MRI and multivariate analyses, we demonstrate that honesty-based trustworthiness is represented in the posterior cingulate cortex, dorsolateral prefrontal cortex and intraparietal sulcus. Crucially, brain signals in these regions predict individual trust in a subsequent social interaction with the same partner. Honesty recruited the ventromedial prefrontal cortex (VMPFC), and stronger functional connectivity between the VMPFC and temporoparietal junction during honesty encoding was associated with higher trust in the subsequent interaction. These results suggest that honesty signals in the VMPFC are integrated into trustworthiness beliefs to inform present and future social behaviors. These findings improve our understanding of the neural representations of an individual’s social character that guide behaviors during interpersonal interactions.