Equality versus self-interest in the brain: Differential roles of anterior insula and medial prefrontal cortex

► We manipulate equality and self-interest of the offer in a modified Ultimatum Game. ► Participants reject unequal and self-disadvantageous offers. ► Anterior insula signals inequality, independently of self-interest. ► Inequality is interpreted as a violation of expected outcome. ► Medial prefrontal cortex processes self-interested motivations.