title: Where is the light? Bayesian perceptual priors for lighting direction.
abstract: Perception of shaded three-dimensional figures is inherently ambiguous, but this ambiguity can be resolved if the brain assumes that figures are lit from a specific direction. Under the Bayesian framework, the visual system assigns a weighting to each possible direction, and these weightings define a prior probability distribution for light-source direction. Here, we describe a non-parametric maximum-likelihood estimation method for finding the prior distribution for lighting direction. Our results suggest that each observer has a distinct prior distribution, with non-zero values in all directions, but with a peak which indicates observers are biased to expect light to come from above left. The implications of these results for estimating general perceptual priors are discussed.
authors.affiliation: Department of Psychology, University of Sheffield, Sheffield S10 2TP, UK. j.v.stone@shef.ac.uk
authors.forename: J V
authors.initials: JV
authors.lastname: Stone
authors.forename: I S
authors.initials: IS
authors.lastname: Kerrigan
authors.forename: J
authors.initials: J
authors.lastname: Porrill