To believe or not to believe: trust choice modulates brain responses in outcome evaluation.

Making a trust decision in interpersonal relationship involves forming positive expectation toward the decision outcome. Previous studies have suggested that trust and distrust are qualitatively distinct and have differential neurocognitive substrates. In this study, we investigated how trust choice would modulate brain responses to decision outcome in a modified coin-toss game. Participants received statements from partners concerning the results of coin-toss and decided whether to believe the truthfulness of the statements. In two experiments, event-related potentials (ERPs) to the real results revealed after the trust choice demonstrated differential patterns following trust and distrust choices. Both the feedback-related negativity (FRN) and the P300 showed effects of outcome valence following trust choices, but the FRN effect was reduced following distrust choices. Thus, trust choice creates different contexts in which aspects of decision outcome can be encoded simultaneously by the FRN. The FRN may reflect the subjective evaluation of decision outcome in a specific context rather than a general expectancy towards the outcome.