A method for analyzing the dimensions of preattentive visual sensitivity

Abstract

A fundamental question in vision science is: Which physical differences in the visual input are spontaneously visible and which are not? At present this question has only been partially answered. We propose that spontaneously visible variations are coded in “field-capture channels” that compute statistics on the raw visual input and pass them on to higher level processes. We describe a psychophysical method for exhaustively deriving the sensitivities of perceptually-available field-capture channels and thereby determining the dimensionality of early visual processes. The description of the field-capture channels resident in human vision will take the form of a compendium of dimensions of preattentive visual sensitivity. Here we demonstrate a method for deriving this compendium. In particular, we apply the method in a domain of physical variation (textures defined by randomly scrambled mixtures of different gray levels) for which the experimental data are available. A simulation shows that the method can (1) determine the number of field-capture channels that are differentially sensitive to variations in the domain and (2) derive a set of basis functions of the space of physical variations to which those channels are sensitive.