ANOMALOUS AND LUMINANCE CONTOURS PRODUCE SIMILAR ANGULAR INDUCTION EFFECTS

One can shear a pattern of lines to produce an anomalous contour which has a perceptual influence similar to that of a straight line segment . Illusion effects have been found with configurations which contain t hese anomalous contours, as well as cross adaptation with respect to l uminance contours. We have found that sheared-line contours will bias judgment of collinearity, ie perceived alignment, of a luminance conto ur. The angular induction effects are similar to those reported for in teractions between luminance contours, and the same equation can be us ed to model both kinds of data. The results of this experiment support the neuroreductionist view that anomalous and luminance contours are processed at the same level of the nervous system. Additionally, we su ggest that with both types of contour the perceptual system registers and responds to the alignment of local brightness differentials.