Different effects from spatial frequency masking in texture segregation and texton detection tasks

The paper reports psychophysical experiments set up to study the visual cues used in texture discrimination. In particular, the special role of "textons", i.e. distinct visual features such as blobs of different size, lines at different orientation, line intersections ("crossings") and line ends ("terminators") which have been proposed to provide the basis of perceptual segregation of texture areas, has been investigated. Texture pairs were briefly presented and simultaneously masked with two-dimensional visual noise at various spatial frequency bands. In different tasks on similar patterns, observers had to estimate the orientation of globally dissecting texture areas ("texture segregation") and to identify and distinguish the texture elements themselves ("texton detection"). Differential masking effects between these tasks indicate that texture segregation is often based on visual cues different from the supposed texton features. The segregation of crossing or terminator differences is also achieved from associated differences in the spatial frequency composition, that of differences in blob size from associated differences in mean luminance. Only differences in line orientation revealed similar masking curves in texture segregation and texton detection tasks.