Neural correlates of the rejection of unfair offers in the impunity game.
This study examined the roles of the insula and the anterior cingulate activations in the rejection of unfair offers in the impunity game. Fifteen participants played the impunity game in ten trials as responders during neuroimaging. About 45% of the unfair offers were rejected by the responders even when responders could not restore a fair outcome, which cannot be accounted for by social preference of inequity aversion. Imaging data showed that the right anterior insula was activated when participants faced and rejected unfair offers. The insula activation during a rejection of the unfair offers is the reflection of an emotional response, rather than social preference of inequity aversion. The role of emotion in the neuroeconomics of fairness was demonstrated.