June 2006
Volume 6, Issue 6
Free
Vision Sciences Society Annual Meeting Abstract  |   June 2006
Dichoptic difference thresholds for familiar and unfamiliar transformations of real scenes
Author Affiliations
  • Ali Yoonessi
    McGill Vision Research, Department of Ophthalmology, McGill University, Montreal H3A 1A1, Canada
  • Frederick A. A. Kingdom
    McGill Vision Research, Department of Ophthalmology, McGill University, Montreal H3A 1A1, Canada
Journal of Vision June 2006, Vol.6, 473. doi:10.1167/6.6.473
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      Ali Yoonessi, Frederick A. A. Kingdom; Dichoptic difference thresholds for familiar and unfamiliar transformations of real scenes. Journal of Vision 2006;6(6):473. doi: 10.1167/6.6.473.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Aim. We have previously shown that sensitivity to photometric (colour and luminance) transformations in images of real scenes is lower for familiar compared to unfamiliar transformations. This suggests a normalization, or gain reduction, of familiar transformations. At what stage does this normalization occur? We tested whether it occurred before or after the stage of binocular combination by measuring dichoptic difference thresholds, or DDTs (the DDT is the just detectable between-eye difference in a binocularly superimposed image-pair), for photometrically-transformed real scenes, and comparing these with conventional image-difference thresholds. Methods. Stimuli were fifty calibrated color photographs of real scenes. The chromaticity and saturation of every image pixel was represented as a vector in a modified version of the MacLeod-Boynton color space, and could be translated, rotated, compressed or randomly repositioned within that color space. The dichoptic image pairs were presented via a modified Wheatstone stereoscope, while the conventional image pairs were presented with the stereoscope removed. All thresholds were measured using 2AFC. Results. DDTs, unlike the conventional image difference thresholds, were more or less constant, i.e. unaffected by familiarity. Conclusion. The result suggests that the normalization process happens after the stage of binocular combination.

Yoonessi, A. Kingdom, F. A. A. (2006). Dichoptic difference thresholds for familiar and unfamiliar transformations of real scenes [Abstract]. Journal of Vision, 6(6):473, 473a, http://journalofvision.org/6/6/473/, doi:10.1167/6.6.473. [CrossRef]
Footnotes
 Supported by Canada Institute of Health Research grant #MOP-11554 given to F.K.
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