Friendship modulates physical effort and neural dynamics during group coordination in shared social networks
Human social interactions are embedded within social networks, yet how existing interpersonal relationships influence the behavioural and neural dynamics of collective action remains unclear. We combined social network mapping with three-person EEG-hyperscanning to investigate how friendship asymmetry within shared social networks modulates physical effort allocation during real-time coordination. Triads consisting of two close friends and one non-friend performed a novel joint force task. Non-friends consistently produced greater and more vigorous force relative to friends, particularly those embedded in smaller classroom social networks. At the neural level, non-friends also showed stronger alpha- and beta-band event-related desynchronization, inter-subject correlation, and group phase synchrony, indicating greater engagement of action-related and attentional processes. These findings suggest that non-friends invest more physical effort and attention when interacting in socially asymmetric group settings, demonstrating how real-world relational context within social networks is dynamically embodied in the neural and behavioural mechanisms supporting human group coordination.