title: The detection of spatial discontinuities: interactions between contrast and spatial contiguity.
abstract: Thresholds were measured for the detection of spatial discontinuities (notches and bumps) along luminance boundaries. At high contrasts of the boundary, thresholds expressed in terms of the spatial notch/bump height fell well inside the hyperacuity range. Expressed as luminance increment thresholds between adjacent photoreceptors, the same thresholds were similar to those previously reported by Hartridge and by Hecht and Mintz for the detection of a single line. The ability of observers to detect differences in the height of a boundary on either side of a mean luminance gap was also investigated, and the effect of the gap was found to depend upon stimulus contrast. At high contrasts the introduction of a gap increased thresholds, but at the lowest contrasts, thresholds were unaffected by a gap. The role of different spatial frequency and orientational mechanisms in vernier acuity is discussed.
authors.affiliation: Department of Psychology, University College London, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Morgan
mesh_terms: D015350:Contrast Sensitivity / Q000502:physiology*; D005556:Form Perception; D006801:Humans; D008027:Light; D011601:Psychophysics; D012684:Sensory Thresholds; D013028:Space Perception / Q000502:physiology*; D014792:Visual Acuity