Individual contributions to (re-)stabilizing interpersonal movement coordination.

Interpersonal movement coordination is characterized by stable coordination patterns. We examined the extent to which the two individuals within a dyad contributed to the stabilization of a shared coordination pattern. Within each dyad, the two participants coordinated rhythmic movements of their right lower arms in either in-phase or antiphase. We analyzed the responses to precisely controlled mechanical perturbations to one of the arms that disrupted the coordination pattern. Return to the original coordination pattern did not only involve phase adaptations in the perturbed arm, but in the unperturbed arm as well. Hence, the coupling between the companions was bidirectional and subserved the coordinative stability. Moreover, for both coordination patterns the interpersonal coupling was near symmetrical, with both actors (perturbed and unperturbed) contributing to the same extents to the restabilization of the coordination between them. The applied methodology provides a new entry point to examine asymmetries in interpersonal coupling, due to, for instance, social impairments, differences in social competence, or particular task setting.