History of one's own performance modulates evaluative processing of another's action outcomes, but not vice versa.

In action monitoring, i.e., evaluating an outcome of our behavior, a reward prediction error signal is calculated as the difference between actual and predicted outcomes and is used to adjust future behavior. Previous studies demonstrate that this signal, which is reflected by an event-related brain potential called feedback-related negativity (FRN), occurs in response to not only one's own outcomes, but also those of others. However, it is still unknown if predictions of different actors' performance interact with each other. Thus, we investigated how predictions from one's own and another's performance history affect each other by manipulating the task difficulty for participants themselves and their partners independently. Pairs of participants performed a time estimation task, randomly switching the roles of actor and observer from trial to trial. Results show that the history of the other's performance did not modulate the amplitude of the FRN for the evaluation of one's own outcomes. In contrast, the amplitude of the observer FRN for the other's outcomes differed according to the frequency of one's own action outcomes. In conclusion, the monitoring system tracks the histories of one's own and observed outcomes separately and considers information related to one's own action outcomes to be more important.