Dopaminergic modulation of the sense of agency influences moral behavior in Parkinson’s disease

Abstract

Embodied accounts of morality propose that corporeal self-awareness helps restrain immoral actions. The Sense of Agency (SoA)—the feeling of controlling one’s actions and their consequences—drops when individuals harm others. However, whether modulating SoA shifts moral behavior remains unclear. Parkinson’s Disease (PD) offers a unique model to address this question, because dopaminergic dysfunction affects both SoA and moral decision-making. We tested 23 individuals with PD in ON and OFF dopaminergic state, and 24 healthy controls using two tasks assessing SoA (SoA-GAME) and moral decision-making (Temptation to Lie Card Game, TLCG), respectively. The SoA-GAME quantified perceived synchrony between executed and observed virtual actions, indexing SoA changes driven by action-related prediction errors (PEs). The TLCG measures self-serving dishonesty by tempting participants to deceive another player for monetary gain. Dopaminergic medication increased SoA relative to OFF state—especially when virtual movements matched participants’ movements but failed to achieve the intended goal—and was associated with reduced dishonest behavior. Drift diffusion modeling showed that dopaminergic state modulated the accumulation of evidence underlying agency judgments, specifically in response to action-related PEs. Critically, higher perceived synchrony in the SoA-GAME predicted a reduction of dishonest choices, but only when individuals with PD were tested ON dopaminergic medication. These findings indicate that dopaminergic modulation of SoA and of the action-related PEs that inform it can influence moral behavior, supporting a direct connection between corporeal self-awareness and morality.