title: Visual discrimination of local surface structure: slant, tilt, and curvedness.
abstract: In four experiments, observers were required to discriminate interval or ordinal differences in slant, tilt, or curvedness between designated probe points on randomly shaped curved surfaces defined by shading, texture, and binocular disparity. The results reveal that discrimination thresholds for judgments of slant or tilt typically range between 4 degrees and 10 degrees; that judgments of one component are unaffected by simultaneous variations in the other; and that the individual thresholds for either the slant or tilt components of orientation are approximately equal to those obtained for judgments of the total orientation difference between two probed regions. Performance was much worse, however, for judgments of curvedness, and these judgments were significantly impaired when there were simultaneous variations in the shape index parameter of curvature.
authors.affiliation: Department of Psychology, Western Kentucky University, Bowling Green, KY 42101-1030, USA. Farley.Norman@wku.edu
authors.forename: J Farley
authors.initials: JF
authors.lastname: Norman
authors.forename: James T
authors.initials: JT
authors.lastname: Todd
authors.forename: Hideko F
authors.initials: HF
authors.lastname: Norman
authors.forename: Anna Marie
authors.initials: AM
authors.lastname: Clayton
authors.forename: T Ryan
authors.initials: TR
authors.lastname: McBride
mesh_terms: D003867:Depth Perception / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology*; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D007600:Judgment / Q000502:physiology; D009949:Orientation; D010775:Photic Stimulation / Q000379:methods; D011594:Psychometrics; D012684:Sensory Thresholds / Q000502:physiology; D015357:Vision Disparity / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology