The neural basis of the Machiavellians' decision making in fair and unfair situations

Although previous research has revealed a number of social, cognitive and neural components of Machiavellians' decision making processes, less attention has been given to the neural correlates of the high Mach (HM) and low Mach (LM) people's responses to situations involving risks and costs imposed by others in interpersonal relationships. In the present study, we used an fMRI technique to examine individuals as they played the Trust game in fair and unfair situations. Our results revealed that the social environment involving opportunities for exploiting others may be more demanding for Machiavellians who showed elevated brain activities in the fair condition (where the partner made a cooperative initiation) but not in the unfair condition. Regarding the specific activated brain areas in the fair condition, the HM's anterior dorsolateral prefrontal cortex (DLPFC) was responding, which is likely to be involved in the inhibition of the prepotent social-emotional response to the partner's cooperative initiative. Furthermore, we found increased activity in the HM subjects' inferior frontal gyrus (IFG), compared to LMs, that plays a crucial role in the evaluation of the signals associated with the others' social behavior, especially when the player faces a cooperative partner. Alternatively, although Machiavellians are regarded as poor mind readers, inferior frontal gyrus may be effective in anticipating their partner's subsequent decisions in the social dilemma situation.