Effects of group affiliation on neural signatures of fairness norm violations in antisocial violent offenders.

While norm-violating behavior in antisocial individuals has been widely studied, little is known about how these people react to unfair behavior directed towards them. Previous research yields inconclusive results with some evidence for rational and strategic behavior in antisocial individuals. Electrophysiological correlates as well as socio-contextual factors such as group affiliation that may inform decision making on fairness considerations have not been investigated in previous studies. This study compared fairness considerations of antisocial violent offenders (N = 25) and controls (N = 26) by using the Ultimatum Game where one player proposes a split of resources and the other player has to respond by accepting or declining the offer. Group affiliation of the proposer (in- vs. out-group) and fairness of offers (fair vs. unfair) were manipulated. We found no difference between groups regarding decision behavior. However, healthy participants showed an electrophysiological response to group affiliation, which was attenuated in the violent offender group. This data suggests intact understanding of social norms in antisocial violent offenders while electrophysiological response pattern may be linked to impaired emotional reactions to expectancy violations.