Behavioral Dynamics of Heading Alignment in Pedestrian Following

The collective behavior of crowds is thought to emerge from local interactions between pedestrians. One widely assumed interaction is heading alignment. We tested four dynamical models of alignment against human data from pairs of pedestrians. A “follower” walked with a “leader” while head trajectories were recorded. In the simplest model, the follower's angular acceleration is proportional to the sine of the heading difference (r=0.71); additional damping or delay parameters did not improve the fit. We conclude that alignment is controlled by nulling the heading difference. The results provide a cognitively- grounded model of alignment that may be generalized to larger crowds.