Feedback-related negativity (FRN) and theta oscillations: Different feedback signals for non-conform and conform decisions

•Outcome evaluation of conformity decisions was encoded by different brain signals.•Increase in FRN was observed in incorrect self-opinion-based Non-Conform decision.•Theta (beta) indexed incorrect (correct) others-opinion-based Conform decision.•FRN and theta served as error signals to guide subsequent conformity behavior.•FRN and theta are functionally dissociated when self and others are in conflict. The current study investigated if feedback-related negativity (FRN) and mid-frontal theta oscillations would respond differently during the outcome evaluations of conformity decisions, which were consistent with self vs. others’ opinions. Participants first performed a perceptual judgment task, then saw the majority opinion prior to submitting their final decision, and subsequently learned whether their final decision was correct. With incongruent initial self and others’ opinions, the incorrect feedback to a non-conform (no-change) final decision elicited larger FRN while the incorrect feedback to a conform (change) decision elicited larger theta power, compared to their respective correct decisions. In addition, beta power was larger in the correct than incorrect conform decision. FRN and theta power, but not beta power, were associated with subsequent conformity behavior. The FRN and theta signals therefore demonstrated differential sensitivity to the source of information that drove a conformity decision.