title: The role of remote closure in the perception of occlusion at junctions and illusory contours.
abstract: Abstract. Perceived occlusion at T-junctions or illusory contours at implicit T-junctions are often modelled by using edge information without surface context. We explored the effect of closure on perceived occlusion at T-junctions. Two vertical lines separated by a gap each had six abutting horizontal lines on opposite sides forming T-junctions. These lines were either closed or not closed into pairs at the stem ends of the Ts. In experiment 1, closed T-junction stems gave a much stronger sense of occlusion at the vertical lines than unclosed ones, even though closure information was remote from the putative occlusion and local T-junction information remained constant. When the outer two T-junctions were converted to L-junctions, perceived occlusion considerably diminished. The effect of closure on illusory-contour strength for stimuli like those of experiment 1 but with the vertical lines omitted was explored in experiment 2. The two sets of horizontal lines, separated by a gap, were either closed or not closed into pairs at their outer ends. Illusory-contour strength along the vertical alignments was much greater for closed pairs. Line terminations on both sides of the gap enhanced illusory-contour strength, but whether they were collinear or not had little effect.
authors.affiliation: School of Psychology, University of New South Wales (UNSW), Sydney, NSW 2052, Australia. b.gillam@unsw.edu.au
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Gillam
authors.forename: Philip M
authors.initials: PM
authors.lastname: Grove
authors.forename: Jessica
authors.initials: J
authors.lastname: Layden
mesh_terms: D000704:Analysis of Variance; D005556:Form Perception / Q000502:physiology; D006801:Humans; D007600:Judgment / Q000502:physiology; D009903:Optical Illusions; D010775:Photic Stimulation; D014796:Visual Perception / Q000502:physiology*