Neural and Behavioral Responses to Social Norm Violations Across Trust and Fairness Contexts

Fairness and trust are core components of social decision making, yet little is known about how individual differences shape neural responses across these contexts. Because the Trust Game (TG) and Ultimatum Game (UG) involve different forms of norm violation, betrayal and interpersonal unfairness, they allow us to test whether neural responses generalize across social contexts Using fMRI during both the TG and UG, we examined how trait-level social cognition interacts with brain systems supporting norm evaluation. Participants demonstrated robust sensitivity to fairness in the Ultimatum Game. A whole-brain psychophysiological interaction analysis revealed that connectivity between the posterior temporoparietal junction (pTPJ) and dorsolateral prefrontal cortex (dlPFC) during unfair offers from a human partner was moderated by the interaction between Autism Quotient (AQ) scores and dorsal anterior cingulate cortex (dACC) response to betrayal in the Trust Game. Individuals with higher AQ showed distinct patterns of pTPJ-dlPFC coupling depending on their neural sensitivity to trust violations. These findings highlight a cross-task mechanism through which trait-level social cognition and trust-related conflict signals shape network-level responses to interpersonal unfairness.