Dopaminergic Modulation of Sense of Agency Influences Moral Behavior in Parkinson’s Disease

Embodied morality theories propose that corporeal self-awareness is pivotal for refraining from immoral actions. Studies indicate that the Sense of Agency (SoA) – i.e., the feeling of controlling one’s actions and their consequences – is reduced when harming others. Whether modulating SoA impacts moral behavior remains unclear. Crucially, individuals with Parkinson’s Disease (PD) show dopamine-related SoA changes and altered moral decision-making, suggesting that these two processes are related to the dopaminergic system functioning. To probe the link between dopaminergic state, moral behavior and SoA we tested 23 participants affected by Parkinson’s disease (PD) in ON and OFF dopaminergic states, and 24 control participants. They performed two behavioral tasks aimed at measuring SoA (SoA-GAME) and moral decision-making (Temptation to Lie Card Game, TLCG), respectively. The SoA-GAME captures degrees of SoA by collecting synchrony judgments between executed and observed virtual actions. The TLCG measures dishonesty by tempting participants to deceive another player for monetary gain. We found that SOA was higher in ON vs. OFF dopaminergic state – specifically, when virtual movements were congruent with participants’ movements and the goal of the action was not achieved – and that patients with PD deceived less in ON than OFF dopaminergic state. Importantly, higher perceived synchrony in the SoA-GAME predicted a reduction of immoral decision-making in the TLCG, only when individuals were in ON dopaminergic state. Our results indicate that dopaminergic medication may decrease self-serving immoral actions through SoA enhancement and support theories proposing a direct connection between corporeal self-awareness and morality.