Importance of body-part-movements in self-organization of pedestrian crowds

Collective human behavior has been studied through various approaches, including empirical observations, modeling, and experimental studies. These approaches have advanced our understanding of the underlying behavioral mechanisms. However, in most studies, individual people are treated as points or oval shapes, ignoring their physical bodies. To better understand collective behavior, further investigations into the role of body-part-movements are required. To this end, we previously conducted pedestrian crowd experiments of lane formation, where unidirectional lanes are spontaneously generated in bidirectional pedestrian flows, tracking pedestrians’ head, foot, and shoulder movements. In the present study, with newly obtained data, we observed the direct relationship between body-partmovements (i.e., body (shoulder) rotation to avoid collisions) and structural instability of generated lanes. Moreover, we found that experimental manipulation where pedestrians align their footsteps with auditory cues caused larger body rotation in the middle of lane formation process. Our findings indicate that movements of one body part (foot) influences the group-level structure, which in turn influences the movements of another body part (shoulder).