Whose loss is it? Human electrophysiological correlates of non-self reward processing.

To recognize whether another person's action results in a good or bad outcome is imperative for social learning, as well as for understanding the behavior of others in a broad context. Recent studies have reported that a scalp-surface event-related potential (ERP) called medial-frontal negativity (MFN), considered to be an index of negative reward processing, is generated when perceiving not only one's own losses, but also those of others. This suggests that the same neural mechanisms operate in monitoring one's own actions and in perceiving the consequences of the actions of others. To further elucidate the properties of this "observational" MFN, this study examined whether its amplitude differs with different observational targets. In a gambling task, participants observed the performances of non-self agents: a human friend and PC programs. The outcomes of the decisions of these agents were not associated with the participants' own benefits. ERP results showed that the MFN-like pattern was significantly elicited only when observing the outcomes of decisions made by human agents. Furthermore, self-reported measures of empathy were positively associated with the magnitude of the observational MFN. These findings suggest that the neural activity in non-self reward processing reflects a socioemotional state generated by the target of observation, as well as an empathetic trait of the individual.