The perception of cast shadows

When an object casts its shadow on a background surface, the shadow can be about the shape of the object, the shape of the background surface and the arrangement of the object relative to the background. Among ail these roles, we found that cast shadows were perceptually most relevant for the recovery of spatial arrangement especially when the shadow is in motion. This finding is intriguing when one considers the ambiguities in the possible ways that shadow motion can be We reasoned that the visual system must use a priori constraints to disambiguate the cart shadow motion. One of these constraints is that the light source is stationary. Though simple, the stationary-light-source constraint supports which, reliable inferences about the qualitative motions of objects in three dimensions.