Serotonin modulates behavioral reactions to unfairness

Abstract

Serotonin (5-HT) has long been implicated in social behavior and impulsivity, but the mechanisms through which it modulates self-control remain unclear. We observed the effects of manipulating 5-HT function on behavior in the ultimatum game, where players must decide whether to accept or reject fair or unfair monetary offers from another player. Participants with depleted 5-HT levels rejected a greater proportion of unfair offers, but not fair offers, without showing changes in mood, fairness judgment, basic reward processing, or response inhibition. Our results suggest that 5-HT plays a critical role in regulating emotion during social decision-making.

Fig. 1

(A) Diagram (adapted from (4)) illustrating the structure of each one-shot UG. While each offer was on the screen, participants pressed one button to accept, or another button to reject. (B) Types of offers. (C) Rejection rates for fair, unfair, and most unfair offers following ATD and placebo (PLA) treatments. Error bars represent standard errors of the difference between means. *P=0.01 difference between treatments.