Social postural coordination.

The goal of the current study was to investigate whether a visual coupling between two people can produce spontaneous interpersonal postural coordination and change their intrapersonal postural coordination involved in the control of stance. We examined the front-to-back head displacements of participants and the angular motion of their hip and ankle during a visual tracking task performed alone and paired. Our results showed that visually paired participants exhibited spontaneous coordination between the movements of their head, hip, and ankle. Moreover, the visual coupling modified the spontaneous intrapersonal ankle-hip coordination dynamics of participants and their performance during visual tracking. Generally, our findings demonstrated reciprocal relations between intrapersonal and interpersonal coordination during social interaction.