Modulation of the brain activity in outcome evaluation by interpersonal relationship: an ERP study.

Previous event-related potential (ERP) studies employing monetary gambling tasks have demonstrated that the brain responds differentially not only to one's own gain and loss but also to the others' gambling outcomes. Empathy and motivational significance are implicated in the processes of outcome evaluation. This study is to explore to what extent the brain activity is modulated by the interpersonal relationship between the individual and the other agent, who can be a friend or a stranger. Brain potentials were recorded while the participant observed reward feedback to his/her own, his/her friend's, or a stranger's performance in a gambling task. The magnitude and latency of the effect on an early ERP component, the FRN, did not differ between the friend- and the stranger-observation conditions, whereas a late component, the P300, was modulated not only by reward valence but also by the interpersonal relationship between the observer and the other agent. These findings suggest that brain responses in outcome evaluation may be divided into an earlier semi-automatic process and a later cognitive appraisal process and that the interpersonal relationship comes into play mostly in the late attention-sensitive stage.