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Steven L. Buck, R. Joseph DeWenter; Rods influence hue on complex backgrounds. Journal of Vision 2010;10(15):50. doi: 10.1167/10.15.50.
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© ARVO (1962-2015); The Authors (2016-present)
Rod signals influence the hue of an isolated extrafoveal target stimulus, such as a large disc, along both red-green and blue-yellow perceptual hue dimensions (Buck, 2001, 2008). The present study begins to explore how additional background features affect these rod hue biases. We assessed rod influence by comparing wavelengths of spectral unique hues (“Uhues”) under bleached (minimizes rod effects) and dark-adapted (maximizes rod effects) conditions for mesopic stimuli centered 7° from fixation.
In Experiment 1, a 5°-diameter test stimulus was presented either alone or surrounded by a contiguous 10°-outer-diameter annulus. Opponent-colored annuli induced color contrast into Ugreen and Uyellow test stimuli, shifting their spectral loci, but had little effect on rod influence, which remained a blue bias (on Ugreen) or green bias (on Uyellow) independent of color contrast. However, the effects of red or green annuli on Ublue tests varied among observers, sometimes inducing color assimilation rather than contrast. Rod influence was also more variable but generally remained a red bias. Both types of variability may be a result of light levels being photopically lowest for the Ublue conditions.
In Experiment 2, a Mondrian-like stimulus was created from a 5x5 array of rectangular patches. Center-patch wavelength was adjusted to measure spectral Uhue loci. Colors of the other patches varied widely. We found the Mondrian background did not systematically stabilize center-patch hue and reduce rod hue biases across observers or Uhues.
We conclude that rod hue biases appear robust in the face of other independent influences on hue evoked by complex backgrounds.
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