Inequity Aversion Makes Gains Harder: Evidence from Neural dynamics in the ultimatum game

To compare cognitive costs between shifting from “rejecting unfairness to accepting unfairness” versus “accepting fairness to accepting unfairness”, an Ultimatum Game with EEG time-frequency analysis (ERSP) was conducted. Participants either accepted a moderately unfair offer (7:3) after rejecting an extreme unfair one (9:1), requiring suppression of inequity aversion, or accepted the same after a fair offer (5:5), without prior rejection. Behaviorally, acceptance rates did not differ. Neurally, the “reject-to-accept” condition exhibited stronger alpha (7–13 Hz) and beta (13–25 Hz) event-related desynchronization (ERD) in the right temporoparietal junction (rTPJ), indicating higher inhibitory control costs. Findings elucidate adaptive mechanisms balancing emotional aversion and strategic flexibility in social inequality contexts, informing interventions for fairness-sensitive individuals and equitable policy design.