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Kelly E. Neriani, Allen L. Nagy; Combining information in different color mechanisms: use of cardinal color mechanisms vs. higher-order color mechanisms. Journal of Vision 2004;4(8):317. doi: 10.1167/4.8.317.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work in our lab has shown that information coded in different Cardinal color mechanisms can be combined to facilitate search for a color target. In this study we asked if information in putative higher-order color mechanisms tuned to diagonal directions in color space can be combined to facilitate search. Stimuli were small disks presented briefly (0.2 sec) within an annular region centered on fixation. Disks differed in luminance from a uniform gray background so that they were easily visible regardless of chromaticity. A spatial 2AFC task was used to measure thresholds for detecting a target that differed in chromaticity from 9 distractor stimuli. In a heterogeneous condition distractors varied in chromaticity along a line in the cone excitation diagram. The distractor lines were either parallel to a Cardinal axis or oriented at 45° with respect to Cardinal axes. Target chromaticities were selected from lines oriented at either 90° or 45° with respect to each distractor line. A cue at the beginning of a block of trials indicated the distractor chromaticity that would contain the target increment in chromaticity. Thresholds in this heterogeneous condition were compared with thresholds in a homogenous condition with 9 distractors that were uniform in color. Results show that when targets were selected from lines parallel to a Cardinal axis, thresholds in the heterogeneous condition were lower than in the homogenous condition regardless of the orientation of the distractor line, but when the target line was diagonally oriented with respect to Cardinal axes, thresholds in the heterogeneous condition were similar to those in the homogeneous condition regardless of the orientation of the distractor line. Results suggest that information in different Cardinal color mechanisms can be combined to facilitate search, but information in different diagonally tuned higher-order color mechanisms cannot be combined to facilitate search.
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