Change in appearance of textures with randomisation of Fourier phase

Abstract

It is known that humans can discriminate visual textures on the basis of differences in statistics higher than the second order. However, these results have been obtained using artificial textures made up of geometric elements, and the effects of manipulating higher order statistics in textures with a more natural appearance have not been examined quantitatively. We therefore investigate the effect of gradual phase randomisation on the ability of observers to discriminate synthetic textures with a naturalistic appearance. We keep the first and second order statistics of textures constant as phase is randomised, so that any perceived changes are due only to changes in third and higher order statistics. A difference scaling method is used to derive perceptual scales for each observer, and this shows a monotonic effect of the degree of randomisation on appearance. The greatest change is perceived between 20% and 60% randomisation, with little change in appearance above and below this range. We propose a biologically plausible model based on a local measurement derived using phase congruence information to account for the observed effects of phase randomisation on discrimination of texture pairs. We show that the same behaviour can be achieved in both perceptual and feature spaces, which can be related by a linear relationship within a log-log space.