Scaling of Perceived Optical Distortion

Abstract

When observers make subjective judgments about a physical stimulus attribute, one is studying the relationship between physical and psychological scales. If the physical stimulus is clearly multidimensional, the relationship of the physical and psychological scales is not always obvious. We have carried out two studies to explore scaling of patterns that simulate optically induced visual distortions. In the first study, subjects rank-ordered computer generated sine wave patterns in order of distortion severity. The rankings corresponded to the physical parameters of frequency and amplitude. In the second study, all possible pairs of 48 stimuli were rated on a dissimilarity index. The data were analyzed by a non-metric multidimensional scaling procedure. We found that a third dimension, in addition to frequency and amplitude was necessary to adequately describe the data.