Abstract
Illusory contours (ICs) provide some of the most compelling data demonstrating the visual system's capacity to synthesize structure that is not present in the input. One theoretical view is that ICs are generated by processes that attempt to provide the best explanation of the input, whereas others explain IC synthesis at an implementation (mechanistic) level of analysis. Here, we report a broad new class of extremely robust IC displays that appear to support implementation level models. We created displays containing thin radial lines ("spokes"). An occluding figure consisting of a 'spiky' circular disk was placed at the center of the display and rotated over the radial spokes. The contrast of the occluding figure relative to the surround, number of spokes, and the number and amplitude of the occluding spikes were parametrically varied. We observed a striking variety of extremely vivid ICs, which appeared to rotate under the physically visible occluding surface. These ICs could take on dramatically different shapes, rigidity, and perceived motion as function of the number of spikes and spokes. The perceived strength of these ICs decreased monotonically as the contrast of the occluding figure increased, but remained visible over all but the highest level of contrast. We psychophysically measured the strength and shape of the ICs. We show that the shapes and motion of the ICs can be well explained by a model of partial border ownership, and develop a model that can accurately predict the perceived shape and motion of these different ICs. Our results suggest that the ICs formed by the accretion and deletion of thin contours are difficult to reconcile with models that attempt to treat IC formation as rational perceptual inference.
Meeting abstract presented at VSS 2018