Effects of local information and egocentric reference frames on estimation of biological motion direction

Previous studies have established that coarse discrimination (e.g., left/right, forward/backward) of point-light walker (PLW) direction is modulated by multiple factors including global/local motion information, biological/social factors, and egocentric reference frames. However, the specific contributions of local motion information and egocentric referencing to fine-grained PLW direction estimation remain unclear. Drawing upon principles of biomechanical asymmetry and right-lateralized motor dominance, we hypothesized a systematic overall rightward bias in PLW direction estimation. Through three carefully controlled experiments, we demonstrated that: (1) right-handed participants showed consistently overall rightward estimation bias; (2) this bias was selectively enhanced by right-sided body stimuli while remaining unaffected by left-sided stimuli; and (3) spatial decoupling of stimulus center from egocentric coordinates revealed persistent egocentric coding in the direction estimation. Moreover, prolonged stimulus exposure led to expanded gaze distribution alongside heightened local information processing, underscoring the pivotal role of local information. These findings suggest that biomechanical asymmetries may shape PLW direction perception and reveal the interplay between local information analysis and egocentric referencing in fine-grained biological motion estimation.