The visual system relies on two types of information to interpret a visual
scene: the cues that can be extracted from the retinal images and prior con
straints that are used to disambiguate the scene. Many studies have looked
at how multiple visual cues are combined. We examined the interaction of mu
ltiple prior constraints. The particular constraints studied here are assum
ptions the observer makes concerning the location of the light source (for
the shading cue to depth) and the orientation of a surface (for depth based
on image contours). The reliability of each of the two cues was manipulate
d by changing the contrast of different parts of the stimuli. We developed
a model based on elements of Bayesian decision theory that permitted us to
track the weights applied to each of the prior constraints as a function of
the cue reliabilities. The results provided evidence that prior constraint
s behave just like visual cues to depth: cues with more reliable informatio
n have higher weight attributed to their corresponding prior constraint. (C
) 2001 Elsevier Science Ltd. All rights reserved.