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Illumination discrimination in the absence of a fixed surface-reflectance layout.

Radonjić, Ana and Ding, Xiaomao and Krieger, Avery and Aston, Stacey and Hurlbert, Anya C. and Brainard, David H. (2018) 'Illumination discrimination in the absence of a fixed surface-reflectance layout.', Journal of vision., 18 (5). p. 11.

Abstract

Previous studies have shown that humans can discriminate spectral changes in illumination and that this sensitivity depends both on the chromatic direction of the illumination change and on the ensemble of surfaces in the scene. These studies, however, always used stimulus scenes with a fixed surface-reflectance layout. Here we compared illumination discrimination for scenes in which the surface reflectance layout remains fixed (fixed-surfaces condition) to those in which surface reflectances were shuffled randomly across scenes, but with the mean scene reflectance held approximately constant (shuffled-surfaces condition). Illumination discrimination thresholds in the fixed-surfaces condition were commensurate with previous reports. Thresholds in the shuffled-surfaces condition, however, were considerably elevated. Nonetheless, performance in the shuffled-surfaces condition exceeded that attainable through random guessing. Analysis of eye fixations revealed that in the fixed-surfaces condition, low illumination discrimination thresholds (across observers) were predicted by low overall fixation spread and high consistency of fixation location and fixated surface reflectances across trial intervals. Performance in the shuffled-surfaces condition was not systematically related to any of the eye-fixation characteristics we examined for that condition, but was correlated with performance in the fixed-surfaces condition.

Item Type:Article
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Available under License - Creative Commons Attribution.
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1167/18.5.11
Publisher statement:Copyright 2018 The Authors This work is licensed under a Creative Commons Attribution 4.0 International License.
Date accepted:No date available
Date deposited:14 June 2018
Date of first online publication:21 May 2018
Date first made open access:No date available

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