Reliability and dimensionality of judgments of visually textured materials

We extended perceptual studies of the Brodatz set of textured materials. In the experiments, texture perception for different texture sets, viewing di stances, or lighting intensities was examined. Subjects compared one pair o f textures at a time. The main task was to rapidly rate all of the texture pairs on a number scale for their overall dissimilarities first and then fo r their dissimilarities according to six specified attributes (e.g., textur e contrast). The implied dimensionality of perceptual texture space was usu ally at least four, rather than three. All six attributes proved to be usef ul predictors of overall dissimilarity, especially coarseness and regularit y. The novel attribute texture lightness, an assessment of mean surface ref lectance, was important when viewing conditions were wide-ranging. We were impressed by the general validity of texture judgments across subject, text ure set, and comfortable viewing distances or lighting intensities. The att ributes are nonorthogonal directions in four-dimensional perceptual space a nd are probably not narrow linear axes. In a supplementary experiment, we s tudied a completely different task: identifying textures from a distance. T he dimensionality for this more refined task is similar to that for rating judgments, so our findings may have general application.