How friendly is a little friendly competition? Evidence of self-interest and empathy during outcome evaluation.

Although previous studies have shown that brain potentials recorded from passive observers differ when gambling-task outcomes are delivered to a friend or a stranger, it is unclear how these outcome evaluations are reflected in brain potentials during active competition. The present study recorded event-related potentials (ERP) from 16 normal adults playing an interactive gambling task against both a friend and a stranger. In this task, the P300 was modulated by the feedback valence (gain or loss) and the nature of the interpersonal relationship, such that it was larger when competing against strangers. Regression analyses indicated that empathy to another's personal distress was negatively related to P300 amplitudes when competing against friends. The dFRN, defined as the difference between losses and gains, varied with Perspective-Taking when competing against friends, such that smaller dFRN amplitudes were correlated with increased Perspective-Taking. The modulation of ERP components indicates that interpersonal relationships may influence outcome evaluations in competitive situations. Correlations between ERP components and empathy measures also provide preliminary support of a relationship between one's empathy and the processing of outcomes during competition against a friend.