Beauty affects fairness: facial attractiveness alters neural responses to unfairness in the ultimatum game.

Human faces consist of rich information for social interactions and facial attractiveness is a key dimension affecting social decisions. Previous studies have indicated that human players are less likely to refuse an unfair offer from proposers with high facial attractiveness in the Ultimatum Game (UG). However, the neural mechanisms underlying such beauty premium effect remain unclear. In this study, we used functional magnetic resonance imaging (fMRI) and examined the effects of facial attractiveness on brain responses to fair and unfair offers in the UG. Behavioral data showed that subjects were overall prone to refuse unfair offers across conditions but were more likely to accept unfair offers from higher facial attractive proposers than those from lower facial attractive proposers. Imaging data showed that unfair offers induced greater activity in the anterior insula and medial prefrontal cortex (MePFC) compared to those in fair offers condition for both high and low facial attractive proposers. Moreover, the acceptance rate of unfair offers positively correlated with the MePFC activity for high facial attractive proposers and negatively correlated with the anterior insula activity for low facial attractive proposers. These findings suggest that facial attractiveness modulates brain responses to unfairness through altering the roles of emotion and cognitive motivation in social interactions.