How body knowledge shapes motion perception

Human motion perception is crucial for social interactions. There is evidence that this perception is influenced by the knowledge of our body and its range of movement. We run two experiments to understand how robust this influence can be. First, we compared human and clock hand motion perception through an apparent motion paradigm. Second, we used a masked priming paradigm to explore how unconscious processes affect motion perception. While the clock hand rotations were generally perceived as clockwise, the human hands were perceived as rotating clockwise and counterclockwise, and their perception was predominantly aligned with biomechanical constraints. The main finding was that this alignment persisted under visual priming for human hands but not for clock hands. The priming effect was significantly reduced when the primed direction conflicted with biomechanically possible hand movements. This suggests that body knowledge shapes motion perception, with this effect proving highly robust.