title: Contour inflections are adaptable features.
abstract: An object's shape is a strong cue for visual recognition. Most models of shape coding emphasize the role of oriented lines and curves for coding an object's shape. Yet inflection points, which occur at the junction of two oppositely signed curves, are ubiquitous features in natural scenes and carry important information about the shape of an object. Using a visual aftereffect in which the perceived shape of a contour is changed following prolonged viewing of a slightly different-shaped contour, we demonstrate a specific aftereffect for a contour inflection. Control conditions show that this aftereffect cannot be explained by adaptation to either the component curves or to the local orientation at the point of inflection. Further, we show that the aftereffect transfers weakly to a compound curve without an inflection, ruling out a general compound curvature detector as an explanation of our findings. We assume however that there are adaptable mechanisms for coding other specific forms of compound curves. Taken together, our findings provide evidence that the human visual system contains specific mechanisms for coding contour inflections, further highlighting their role in shape and object coding.
authors.affiliation: School of Psychology, University of Western Australia, Crawley, AustraliaMcGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Bell
authors.affiliation: School of Psychology, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Sinthujaa
authors.initials: S
authors.lastname: Sampasivam
authors.affiliation: Multisensory Cognition Group, Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland.
authors.forename: David P
authors.initials: DP
authors.lastname: McGovern
authors.affiliation: Institut de Neuroscience de la Timone, UMR 7289 CNRS & Aix-Marseille Université, Marseille, France.
authors.forename: Andrew Isaac
authors.initials: AI
authors.lastname: Meso
authors.affiliation: McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, Quebec, Canada.
authors.forename: Frederick A A
authors.initials: FA
authors.lastname: Kingdom
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D003463:Cues; D005260:Female; D005366:Figural Aftereffect / Q000502:physiology*; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D009949:Orientation; D010775:Photic Stimulation
keywords: aftereffects; contour; curvature; inflection; shape