title: Parallelism and the perception of illusory contours.
abstract: The role of symmetry in the perception of illusory contours has been a subject of controversy ever since Kanizsa proposed his theory of illusory contours based on Gestalt principles. Today it is widely agreed that illusory contours do not necessarily occur more readily with inducers that can be 'amodally' completed to symmetrical objects than with inducers that cannot. But the question of whether symmetrical inducers produce weaker illusory contours than do unsymmetrical ones is still controversial. A novel determinant of illusory contour strength, parallelism, is proposed. Experiments are reported which indicate that illusory contours induced by 'blobs' which have boundaries that are nearby and parallel to the illusory contour are weaker than illusory contours induced by blobs that do not have this property. It is suggested that the display that has been most widely used by researchers to support their claims for a weakening of illusory contours with symmetrical inducers is weak primarily because of parallelism.
authors.affiliation: Department of Information and Computer Science, University of California at Irvine 92717.
authors.forename: M K
authors.initials: MK
authors.lastname: Albert
mesh_terms: D000328:Adult; D001288:Attention; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D008297:Male; D009903:Optical Illusions; D009949:Orientation; D010364:Pattern Recognition, Visual; D011601:Psychophysics