Serotonin selectively influences moral judgment and behavior through effects on harm aversion

• DOI: 10.1073/pnas.1009396107
• Publication Date: 2010-09-28T04:45:52Z
• Authors: Molly J. Crockett; Luke Clark; Marc D. Hauser; Trevor W. Robbins
• Keywords: Prosocial Behavior; Ultimatum game

Aversive emotional reactions to real or imagined social harms infuse moral judgment and motivate prosocial behavior. Here, we show that the neurotransmitter serotonin directly alters both behavior through increasing subjects’ aversion personally harming others. We enhanced in healthy volunteers with citalopram (a selective reuptake inhibitor) contrasted its effects a pharmacological control treatment placebo on tests of measured drugs' set 'dilemmas' pitting utilitarian outcomes (e.g., saving five lives) against highly aversive harmful actions killing an innocent person). Enhancing made subjects more likely judge as forbidden, but only cases where were emotionally salient. This harm-avoidant bias after was also evident during ultimatum game, which decide accept reject fair unfair monetary offers from another player. Rejecting enforces fairness norm other player financially. less offers. Furthermore, varied function trait empathy. Individuals high empathy showed stronger than individuals low Together, these findings provide unique evidence could promote by enhancing harm aversion, sentiment affects