Interpersonal relationship modulates the behavioral and neural responses during moral decision-making

Interpersonal relationship (IR) may play an important role in moral decision-making. However, it is little known about how IR influences neural and behavioral responses during moral decision-making. The present study utilized the dilemma scenario-priming paradigm to examine the time course of the different intimate IR (friend, acquaintance, or stranger) impacts on the emotional and cognitive processes during moral decision-making. Results showed that participants made less altruistic decisions with increased decision times and experienced more unpleasure for strangers versus friends and acquaintances. Moreover, at the early moral intuitional process, there was no significance difference observed at N1 under different intimate IR; however, at the emotional process, larger P260 which reflects the dilemma conflicts and negative emotional responses, was elicited when moral decision-making for strangers; at the later cognitive process, such difference was also observed at LPP (300–450 ms) which indexes the later top-down cognitive appraisal and reasoning processes. However, such differences were not observed between friends and acquaintances. Results indicate that IR modulates the emotional and cognitive processes during moral decision-making, suggesting that the closer the IR is, the weaker the dilemma conflicts and emotional responses are, and the more efficient this conflicts are solved.