title: Properties of long-range illusory contours produced by offset-arcs.
abstract: Researchers have used several different types of illusory contours to investigate properties of human perception. One rarely used illusory contour is a combination of the abutting grating and Kanizsa illusions. We call this the offset-arcs illusion and provide an empirical investigation of the illusion. Through a series of four experiments, using different methods of measurement, we show that changes to the phase of the abutting-grating part of the inducing stimulus can dramatically change the perceived strength and clarity of the long-range illusory contour. The easy manipulation of illusion strength should make the offset-arcs illusion applicable to a wide range of studies that utilize long-range illusory contours. The lack of a brightness component to the illusion should allow the offset-arcs illusion to help separate perceptual grouping from surface brightness effects that are often confounded in other illusory contours.
authors.affiliation: Department of Psychological Sciences, Purdue University, 703 Third Street, West Lafayette, IN 47907-2004, USA. gfrancis@purdue.edu
authors.forename: Gregory
authors.initials: G
authors.lastname: Francis
authors.forename: Joshua
authors.initials: J
authors.lastname: Wede
mesh_terms: D000704:Analysis of Variance; D005366:Figural Aftereffect / Q000502:physiology*; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D009903:Optical Illusions / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods