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Journal of the Optical Society of America A

Journal of the Optical Society of America A


  • Vol. 20, Iss. 1 — Jan. 1, 2003
  • pp: 11–17

Foveal contrast thresholds exhibit spatial-frequency- and polarity-specific contour interactions

Oliver Ehrt, Robert F. Hess, Cristyn B. Williams, and Khurram Sher  »View Author Affiliations

JOSA A, Vol. 20, Issue 1, pp. 11-17 (2003)

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Traditionally, contour interaction has been investigated at the visual acuity limit using a Landolt C and flanking bars, performance being quantified in terms of a percent correct measure. More recently, it has been shown that the properties of the contour interaction are different when larger stimuli are used: Contour interaction is not polarity specific, and spatial frequency tuning for an unflanked C is broader. Here we quantify contour interaction for stimuli 5× larger than the resolution limit in terms of contrast thresholds. We show that polarity of bars has little effect on unfiltered stimuli but does show very different effects on the spatial-frequency-tuning curves for discrimination of the Landolt C. This explains the polarity dependence of crowding at the visual acuity limit and its independence for larger unfiltered targets. Thus the underlying filtering function is composed of more than one mechanism, affected differently depending on the relative polarity of the test and flank contours.

© 2003 Optical Society of America

OCIS Codes
(330.1800) Vision, color, and visual optics : Vision - contrast sensitivity
(330.5510) Vision, color, and visual optics : Psychophysics
(330.6110) Vision, color, and visual optics : Spatial filtering

Original Manuscript: April 29, 2002
Revised Manuscript: August 13, 2002
Manuscript Accepted: August 22, 2002
Published: January 1, 2003

Oliver Ehrt, Robert F. Hess, Cristyn B. Williams, and Khurram Sher, "Foveal contrast thresholds exhibit spatial-frequency- and polarity-specific contour interactions," J. Opt. Soc. Am. A 20, 11-17 (2003)

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