Neural responses to equity and inequity when receiving vicarious rewards for self and charity during adolescence

This study examined neural responses to inequity aversion for vicarious outcomes involving self and charity in adolescence using fMRI. In three longitudinal waves including participants between ages 11-24-years (wave 1: n=160, 86 females; wave 2: n=165, 84 females; wave 3: n=174, 90 females), we studied neural responses in dorsolateral prefrontal cortex (DLPFC), temporal parietal junction (TPJ), and ventral striatum (VS) using a Prisoner Dilemma-informed paradigm. After each choice between two possible options, participants received rewards either only for self, only for charity, for both, or for neither. Similar as in previous research, activity in VS correlated with self-serving outcomes. In contrast, DLPFC and TPJ showed lowest activity to equity outcomes (mutual benefit) and higher activity to both self-serving and other-serving inequity, suggesting a general role in inequity aversion. Finally, TPJ activity was highest when neither party received a reward, possibly signaling additional demands on social attention switching. Developmental comparisons revealed a shift from stronger activity in VS to self-serving outcomes in early adolescence to stronger activity in DLPFC and TPJ to inequity aversion in late adolescence. Together, these findings suggest more advanced inequity signaling during adolescent development.