Individual locomotor bias drives counterclockwise motion in pedestrian crowds

These experiments investigate why free-roaming pedestrian groups tend to rotate counterclockwise (CCW). Five controlled campaigns in Spain and Japan used circular arenas, an open schoolyard, nursery free play, and single-person trials to measure turning behavior. Individual turning preference was tested by asking volunteers to walk to a wall, turn 180°, and return; collective rotation was quantified with a polarization metric M computed from each pedestrian’s velocity relative to the arena center. Conditions included groups enriched in left-handed or left-turning people, environments without enclosing boundaries, and populations from regions with different counterflow lane biases.

Results show a robust, reproducible CCW bias that appears even when interpersonal or boundary interactions should not generate a group preference: CCW rotation emerged with left-dominant participants, in open spaces, in Japanese samples where counterflows favor left lanes, during children’s play, and for single walkers in isolation. Survey responses and tests of handedness, footedness, and eye dominance fail to account for the effect, leading to the conclusion that a subtle individual locomotor bias - likely biologically rooted - drives collective CCW motion. Findings call for reconsidering assumptions in crowd modeling and have implications for urban design and crowd management, while the precise physiological origin remains unresolved.