title: Effects of contour proximity and lightness on Delboeuf illusions created by circumscribed letters.
abstract: 32 observers judged the size of a letter, either an "A" or an "S," which was surrounded by a circle. Both letters were overestimated, but larger surrounding circles reduced the illusion. Decreasing the lightness contrast of the surrounding circle relative to the central letter diminished the illusion. The results suggest that, like the Delboeuf illusion, these circumscribed letters illusions are produced by interactions among size-coding neurons.
authors.affiliation: Department of Psychology, 501 Westminster Avenue, Westminster College, Fulton, MO 65251, USA. JaegerT@westminster-mo.edu
authors.forename: Ted
authors.initials: T
authors.lastname: Jaeger
authors.forename: Stephen
authors.initials: S
authors.lastname: Long
mesh_terms: D000293:Adolescent; D000328:Adult; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D007600:Judgment / Q000502:physiology; D008297:Male; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology; D009903:Optical Illusions / Q000502:physiology*; D012107:Research Design; D012858:Size Perception / Q000502:physiology