Individual abilities to estimate levels of movement synchrony predict action observation network activation.

Observers' ability to estimate levels of movement synchrony, such as in Olympic diving or rowing, is highly variable and, in part, constrained by personality traits and enjoyment of the movements. Embodiment also appears to play a crucial role, whereby stronger beliefs that one's body can complete physical tasks predict more accurate estimation of synchrony levels. However, to demonstrate the relevance of embodiment per se, direct evidence that physical embodiment (i.e., bodily knowledge of specific movements) alters synchrony estimation is required. Here, we assessed the behavioural and cortical underpinnings of synchrony estimation in conditions with and without physical embodiment. Forty-three participants completed personality trait measures, then completed a synchrony estimation task. Participants copied upper-body movement sequences (acquiring physical embodiment), then viewed dyads performing the same sequence or an unknown sequence and estimated the level of synchrony, while we recorded cortical activation using functional near-infrared spectroscopy (fNIRS). Participants underestimated synchrony levels, showing greater underestimation for unknown movements than performed movements. For performed movements, but not unknown movements, the degree of estimation error was associated with activation of left inferior frontal gyrus and superior temporal gyrus, and right motor cortex and inferior parietal lobule. Participants' estimation error was associated with body competence and autistic trait scores, as well as measures of enjoyment and movement predictability (replicating previous work). This work demonstrates that physical embodiment improves lay observers' ability to discern levels of movement synchrony and has practical implications across a wide variety of artistic and athletic domains.