The sunny side of fairness: preference for fairness activates reward circuitry (and disregarding unfairness activates self-control circuitry).

Little is known about the positive emotional impact of fairness or the process of resolving conflict between fairness and financial interests. In past research, fairness has covaried with monetary payoff, such that the mental processes underlying preference for fairness and those underlying preference for greater monetary outcome could not be distinguished. We examined self-reported happiness and neural responses to fair and unfair offers while controlling for monetary payoff. Compared with unfair offers of equal monetary value, fair offers led to higher happiness ratings and activation in several reward regions of the brain. Furthermore, the tendency to accept unfair proposals was associated with increased activity in right ventrolateral prefrontal cortex, a region involved in emotion regulation, and with decreased activity in the anterior insula, which has been implicated in negative affect. This work provides evidence that fairness is hedonically valued and that tolerating unfair treatment for material gain involves a pattern of activation resembling suppression of negative affect.