Dopamine is one of the brain’s principal neurotransmitters and plays a fundamental role in how we behave, what motivates us, and how we make decisions. It is central to the brain’s so-called reward circuits, which are activated when we engage in pleasurable or rewarding activities. These same circuits are also involved in gambling behaviour and in the way we perceive risk. A new study published in the scientific journal PNAS shows that dopamine can also influence our sense of control over our own actions and, consequently, our tendency to behave fairly towards others.

The study was conducted as part of a large multicentre collaboration involving the Italian Institute of Technology, Sapienza University of Rome, and the IRCCS Santa Lucia Foundation in Rome. The research was coordinated by Salvatore Maria Aglioti, a neurologist, in collaboration with Giorgia Ponsi and Riccardo Villa, both neuroscientists.

To investigate the influence of dopamine on the brain, the research team focused on a group of patients with Parkinson’s disease, a neurological disorder characterised by a deficiency of dopamine that is treated with dopamine-replacement therapies. To compensate for this deficiency, patients with Parkinson’s disease are commonly prescribed levodopa—a precursor of dopamine—or other dopaminergic medications that increase dopamine levels or mimic and enhance its effects.

Specifically, the participants took part in an interactive game in which they were required to make choices that could either benefit or disadvantage another player. This enabled the researchers to assess whether the patients showed a preference for either type of decision, both when they were off their medication and after they had taken it. “We showed patients virtual actions and asked them to take part in an interactive game in which they could receive a reward by lying,” says Giorgia Ponsi and Riccardo Villa. “Using these tools, we tested two processes that we believed to be influenced by dopamine: the sense of being responsible for our own actions and their consequences, and the way we make decisions related to honesty.”

The results show that, after taking medication, participants reported a stronger sense of control over their own actions and were therefore less likely to behave dishonestly towards the other player, compared with when they were off medication, when their sense of control was reduced.

It is known that in more than 10% of patients with Parkinson’s disease, the type of medication used to treat the condition can lead to socially dysregulated behaviour or impulsive financial decision-making, due to its effects on dopamine circuits. The study attributes these behaviours to the modulation exerted by dopamine on the sense of control we have over our own actions.

“The brain does not alter moral decision-making processes because of a lack of dopamine, as we might be inclined to think. Rather, a reduction in this neurotransmitter leads it to diminish the perception of one’s own causal role in generating events: it becomes harder to identify one’s responsibility for actions, even when these have negative consequences for other people,” says professor Salvatore Maria Aglioti.

These results support the idea of a close relationship between bodily awareness and moral behaviour.
This research is part of a broader line of studies that attributes to the basal ganglia—brain regions involved in dopamine production and severely affected in Parkinson’s disease—not only a motor function, but also a role in evaluating the consequences of one’s own actions

From a clinical perspective, the study adds an important piece to our understanding of the effects that dopaminergic treatments may have on social interactions. In addition, it may contribute to the development of more comprehensive and personalised therapeutic approaches for Parkinson’s disease.

The study was carried out in collaboration with the University of Verona, the University Medical Center Hamburg-Eppendorf (UKE), and Ghent University. The authors would like to thank Dr Ilaria Di Vico, Professor Maria Serena Panasiti, Dr Michael Schepisi, and Professor Michele Tinazzi, who supervised the recruitment of the 24 patients.

References: G. Ponsi, R. Villa, I. Di Vico, M.S. Panasiti, M. Schepisi, M. Tinazzi, & S.M. Aglioti, Dopaminergic modulation of the sense of agency influences moral behavior in Parkinson’s disease, Proc. Natl. Acad. Sci. U.S.A. (2026) 123 (17) e2513356123,

DOI: 10.1073/pnas.2513356123

Further Information

Giorgia Ponsi – Department of Psychology

giorgia.ponsi@uniroma1.it