Abstract
Without special training or feedback, observers can make accurate judgements concerning the relative mass of two colliding objects. However, judgments of relative mass are subject to bias, and subjects tend to perceive the initially faster of two collision objects as heavier. This is especially true when physical systems are displayed with a significant loss in kinetic energy after the collision. This bias, the Motor Object Bias, has been understood as a deviation from Newtonian mechanics, suggesting that the visual system is not capable of taking advantage of physical regularities when making physical inferences. Both heuristics and ideal-observer models have been proposed to explain how observers select and utilize kinematic information to obtain a dynamical judgment. Instead, we argue that the visual system may be able to compute a mass ratio based on sensory inputs and Newtonian regularities. However, the process is not atemporal. Rather, the visual system produces mass judgments about objects continuously and from multiple sources of information. We investigate a range of factors that are involved in static mass perception, such as volume and material properties, as well as the momentum cues such as elasticity and relative velocity and found that the physical inconsistency can be easily explained by the commonsense assumption that the visual systems impression of relative mass of two colliding objects is influenced by the impression of mass from static cues, prior to any motion event.