Visual search of illusory contours: The role of illusory contour clarity

Kanizsa-type illusory contours demonstrate an important function of the visual system—object inference from incomplete boundaries, which can be due to low luminance environments, camouflage, or occlusion. At a perceptual level, Kanizsa figures have been shown to have various degrees of clarity, depending on the features of the inducers. The aim of the present study is to evaluate whether contour clarity influences search efficiency of Kanizsa-type illusory contours. Experiment 1 will examine search for a Kanizsa-type illusory target among Kanizsa-type illusory distractors, by manipulating contour clarity using inducer size in three conditions, compared with search for a nonillusory perceptually grouped target among nonillusory perceptually grouped distractors with manipulated inducer size. Experiment 2 will address the effects of contour clarity on visual search by manipulating the number of arcs (i.e., line ends) comprising the inducers, in a visual search task of Kanizsa-type stimuli, compared with visual search for nonillusory grouped targets and distractors when the number of arcs are manipulated. To examine whether surface alterations had an impact on search in Experiment 1 due to changes in inducer size, Experiment 3 will examine search for Kanizsa stimuli formed from “smoothed” inducers, in comparison to search for Kanizsa stimuli used in Experiment 1 . Together, these experiments will demonstrate whether contour clarity impacts visual search of illusory contours.