Pushing the Ball or Pulling the Rubber Band: Material Perception Reverses the Causal Arrow in Agent-Patient Dynamics

We effortlessly recognize various non-rigid materials and predict their behavior from visual cues. However, causal perception research has largely underexplored dynamic interactions involving non-rigid objects, often treating spatiotemporal causality as independent of object properties. This study introduces a novel ambiguous motion stimulus: A line segment elongating with a disc at its end, perceived as either “a disc pulling an elastic band” or “a rigid stick pushing a disc.” Across three experiments (n=138 young adults), causal and material judgments were strongly influenced by acceleration and deceleration patterns. Four follow-up experiments (n=120) using a pause- detection task revealed participants’ sensitivity to dynamics incompatible with the expected behavior of a stretched elastic band, underscoring the visual system’s integration of kinematic patterns into coherent perceptual interpretations. These findings demonstrate how subtle kinematic manipulations can entirely reverse perceived force dynamics, causal roles, and material properties in sync, advancing a unified framework for material and causal perception.