“I will fix only my own mistakes”: An ERP study investigating error processing in a joint choice-RT task

► We show that people monitor both their own and others responses. ► Participants only adjust their performance after own but not others errors. ► Feedback-related ERP components are larger for co-actors than own responses. ► Performance monitoring is not sufficient to trigger control adjustments. The current study investigated error monitoring and subsequent control adjustments in a joint choice RT task. External feedback relating to the combined performance of both actors was provided. Participants slowed down only after their own but not after the co-actor's mistakes. In order to investigate the neural correlates of interpersonal error monitoring, ERPs associated with error processing (Ne/ERN, Pe) and feedback-related processing (FRN, f-P300) were analysed. The Ne/ERN and Pe were only affected by own but not the co-actor's actions. Conversely, at the feedback stage both the FRN and the f-P300 were larger when external feedback indicated a co-actor's error, yet despite this finding, co-actor errors did not affect the actor's subsequent performance. These findings are in line with previous research suggesting that we monitor not only our own but also others’ errors. Importantly, however, monitoring others’ performance seems insufficient to trigger subsequent behavioural adjustment in the form of post-error slowing, but might only occur when a surprising outcome is evaluated as negative.