Relational Dynamics Inform Predictive Motor Planning and Weight Perception

While size and material cues have long been recognized as key drivers of anticipatory load force scaling, dynamic relational interactions may offer an equally potent source of sensorimotor guidance. This study examined whether conservation of momentum influences sensorimotor planning and whether it is perceptually instantiated. We developed a hybrid virtual reality/real-object paradigm in which participants (N=7) observed collisions between visually identical objects that varied only in apparent mass ratios and coefficients of restitution before lifting them. Results revealed that anticipatory forces scaled with inferred mass from collision kinematics, and explicit weight judgments demonstrated a dynamic weight illusion—participants perceived the motor object as heavier when the target object’s inferred mass increased. These findings suggest that conservation of momentum is integrated into both motor planning and perceptual representations, extending our understanding of intuitive physics by demonstrating that the visual system incorporates relational dynamics into sensorimotor processing.