Interpersonal physiological synchrony during dyadic joint actions is increased by task novelty and reduced by social anxiety

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Interpersonal Physiological Synchrony (IPS) refers to the temporal coordination of autonomic states during social interactions. Despite the potential importance of IPS in modulating social functions, a clear understanding of its functional role and the contextual and individual factors that may promote or hinder its emergency, is missing. In the present study, we recorded the cardiac activity of dyads engaged in a cooperative joint action task and measured the degree of IPS occurring during the task. To investigate the role played by contextual factors in the emergence of IPS, we engaged participants in different versions of the task (peer-to-peer vs. leader-follower, complementary vs imitative movements). We explored whether switching compared to repeating the same task version would affect IPS and assessed the influence of dyad members’ social anxiety and perspective-taking abilities on IPS. Our results revealed a significant increase in IPS and a decrease in perceived performance, interaction easiness/pleasantness, and feeling of alignment when participants switched to a new version of the task (i.e., during switch blocks) compared to repeating the same. Task switching was also characterised by an increase in heart rate variability. Social Anxiety negatively predicted IPS, indicating that more socially anxious dyads were less likely to become physiologically aligned. No relationship was observed between IPS and task performance. Overall, this work indicates that IPS increases when the dyad faces the challenges of learning together a new task and that both contextual and individual aspects contribute to its emergence.