How visual information influences coordination dynamics when following the leader.

Coordinating one's movements with others is an important aspect of human interactions. Regulating the distance to other moving agents is often necessary to achieve specific task goals such as in invasion sports. This study aimed to examine how distance regulation is mediated by different sources of information that are typically available when humans coordinate their actions to others. Participants followed a virtual leader that moved backwards and forwards, and were instructed to maintain the initial distance. In one condition, participants were presented with a life-size fully animated human avatar as the leader, displaying both segmental (limb motion) and global (optical expansion) motion information. In the other condition, participants had to follow an expanding and receding sphere in which segmental motion information was absent. Optical expansion rates revealed that participants regulated distance equally effective in both conditions. Given the phase relation and response times to direction changes however, the timing to the leader appeared to be more accurate in the avatar condition. These results provide support that forward-backward following can indeed be successfully mediated through global information, but that detection of segmental information allows for earlier tuning to another person's movement intentions.