Velocity—Not Perceived as Such: The Role of Object Mass in Velocity Estimation

Heavier objects tend to move more slowly than lighter ones, whether we lift them ourselves or observe larger vehicles accelerating more gradually– a relationship constrained by Newtonian law. As our perception of the environment is so tightly guided by the externally available information, it’s natural to ask to what extent sensory processing internalizes these everyday mass–velocity relationships. Contrary to the longstanding assumption that mass and velocity are encoded independently in the mind, across three experiments (N=176), we reveal a novel mass–speed illusion: heavier-looking objects are judged to move more slowly than lighter ones, despite identical retinal speeds and sizes. This bias persists across very different stimulus manipulations and is strikingly uniform across observers. Together, these results demonstrate that the perceptual system internalizes the statistical regularities linking mass and velocity in the natural environment and suggest that the foundations of our intuitive grasp of physics are embedded within early sensory encoding.