Summary: A new double-blind, placebo-controlled study shows that dopamine directly influences mentalising—the ability to infer others’ thoughts, feelings and intentions—in healthy adults. In a trial with 33 volunteers, blocking dopamine receptors with haloperidol reduced accuracy when participants ascribed mental states to animated interactions, highlighting dopamine’s role in socio-cognitive function and carrying implications for conditions such as Parkinson’s disease.
Researchers at the University of Birmingham report these findings in PLOS Biology, demonstrating for the first time a causal link between dopamine signalling and theory of mind (mentalising) performance in healthy individuals.
Key facts
- Dopamine influences the brain processes that support understanding others’ mental states (mentalising/theory of mind).
- The study used haloperidol to block dopamine receptors in 33 healthy volunteers within a double-blind, placebo-controlled design.
- Results indicate that dopamine imbalance can impair socio-cognitive abilities such as emotion recognition and mentalising.
Background
Dopamine is a key neurotransmitter involved in motivation, reward and learning. It is also central to motor control, and diminished dopamine signalling in motor regions underlies core symptoms of Parkinson’s disease. Alongside motor symptoms, people with Parkinson’s commonly experience socio-cognitive difficulties, including problems with emotion recognition and mentalising. Until now, a direct link between dopamine function and these socio-cognitive abilities in healthy people had not been established.
The study design
Lead author Dr Bianca Schuster and colleagues tested 33 healthy adult volunteers using a rigorous double-blind, placebo-controlled protocol. Each participant completed the experimental tasks on two separate days: once after receiving a single dose of haloperidol, a drug that blocks dopamine D2 receptors, and once after receiving a placebo. The order of drug and placebo sessions was counterbalanced across participants to control for practice and order effects.
The primary measure was an animations task commonly used to probe mentalising. Participants watched short videos in which simple geometric shapes—typically triangles—appeared to interact in ways that imply social intentions (for example, chasing, coaxing or helping). After each clip, participants selected the label they felt best described the interaction, allowing researchers to quantify accuracy in attributing mental states.
In a complementary experiment, the team also measured emotion recognition using whole-body point-light displays—videos in which only an actor’s joint movements are visible—to isolate perceptual cues from facial detail (see Schuster et al., 2021, Journal of Neuroscience for related methods and findings).
Findings
Administration of haloperidol reduced participants’ ability to correctly attribute mental states in the animations task compared with the placebo condition. This decrement in mentalising performance was linked to changes in emotion recognition measured with point-light displays, suggesting that dopamine blockade may impair socio-cognitive judgments by altering the perception and interpretation of emotional motion cues.
Dr Schuster explains that while socio-cognitive symptoms are not always the main clinical focus in disorders like Parkinson’s, they have a substantial impact on daily life and social functioning. These results show that dopamine dysfunction can contribute directly to those socio-cognitive impairments, beyond the well-characterised motor effects of dopamine loss.
Implications
The study provides evidence that pharmacological manipulation of dopamine alters theory of mind performance in healthy adults. This has two important implications: first, it suggests that socio-cognitive deficits observed in dopamine-related disorders may stem in part from neurotransmitter imbalance rather than solely from psychosocial factors such as isolation. Second, it highlights the need to consider socio-cognitive side effects when prescribing drugs that affect dopamine signalling, including treatments for Parkinson’s and other conditions.
About this research
Author: Beck Lockwood
Source: University of Birmingham
Contact: Beck Lockwood, University of Birmingham
Image credit: Neuroscience News
Original research: Findings reported in PLOS Biology