Theory of mind and joint action in Parkinson’s disease

Gender composition of pairs influences joint action effect

Research on joint action has demonstrated that individuals are sensitive to a coactor's attentional relation to jointly attend stimuli. It has also been suggested that some features are necessary to resolve the discrimination problem (i.e., self-own and other-own actions). In the present study, we aimed to test whether the gender composition of interacting pairs modulated the joint action effect. Same- (female-female or male-male) and mixed- (female-male) gender pairs performed a joint version of flanker tasks in Experiment 1 (90 participants, 50% males), while in Experiment 2 (154 participants, 50% males) Navon tasks were performed. In Experiment 1, a higher joint flanker effect in same-gender pairs than in mixed-gender pairs, and this joint effect was similar to the classical flanker effect reported by males and females in a classical procedure of the task (70 participants, 50% males). In Experiment 2, the same-gender pairs reported a joint Navon effect, which was reversed in mixed-gender pairs. In conclusion, our findings support how the gender composition of interacting pairs plays a role in joint attentional tasks.

The dopaminergic system supports flexible and rewarding dyadic motor interactive behaviour in Parkinson's Disease

Studies indicate that the dopaminergic system (DAS) supports individual flexible behaviour. While flexibility is quintessential to effective dyadic motor interactions, whether DAS mediates adaptations of one's own motor behaviour to that of a partner is not known. Here, we asked patients with Parkinson's Disease (PD) to synchronize their grasping movements with those of a virtual partner in conditions that did (Interactive) or did not (Cued) require to predict and adapt to its actions. PD performed the task during daily antiparkinsonian treatment ('On' condition) or after drug-withdrawal ('Off' condition). A group of healthy individuals also served as control group. In the Interactive condition, PDs performed better and found the interaction more enjoyable when in 'On' than in 'Off' condition. Crucially, PD performance in the 'On' condition did not differ from that of healthy controls. This pattern of results hints at the key role of the DAS in supporting the flexible adaptation of one's own actions to the partner's during motor interactions.