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Proceedings Paper

Effect of fixation positions on perception of lightness
Author(s): Matteo Toscani; Matteo Valsecchi; Karl R. Gegenfurtner
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Paper Abstract

Visual acuity, luminance sensitivity, contrast sensitivity, and color sensitivity are maximal in the fovea and decrease with retinal eccentricity. Therefore every scene is perceived by integrating the small, high resolution samples collected by moving the eyes around. Moreover, when viewing ambiguous figures the fixated position influences the dominance of the possible percepts. Therefore fixations could serve as a selection mechanism whose function is not confined to finely resolve the selected detail of the scene. Here this hypothesis is tested in the lightness perception domain. In a first series of experiments we demonstrated that when observers matched the color of natural objects they based their lightness judgments on objects’ brightest parts. During this task the observers tended to fixate points with above average luminance, suggesting a relationship between perception and fixations that we causally proved using a gaze contingent display in a subsequent experiment. Simulations with rendered physical lighting show that higher values in an object’s luminance distribution are particularly informative about reflectance. In a second series of experiments we considered a high level strategy that the visual system uses to segment the visual scene in a layered representation. We demonstrated that eye movement sampling mediates between the layer segregation and its effects on lightness perception. Together these studies show that eye fixations are partially responsible for the selection of information from a scene that allows the visual system to estimate the reflectance of a surface.

Paper Details

Date Published: 17 March 2015
PDF: 16 pages
Proc. SPIE 9394, Human Vision and Electronic Imaging XX, 93940R (17 March 2015); doi: 10.1117/12.2175673
Show Author Affiliations
Matteo Toscani, Justus-Liebig-Univ. Giessen (Germany)
Matteo Valsecchi, Justus-Liebig-Univ. Giessen (Germany)
Karl R. Gegenfurtner, Justus-Liebig-Univ. Giessen (Germany)

Published in SPIE Proceedings Vol. 9394:
Human Vision and Electronic Imaging XX
Bernice E. Rogowitz; Thrasyvoulos N. Pappas; Huib de Ridder, Editor(s)

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