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Kenji Yokoi, Keiji Uchikawa; Categorical color mechanism mediates heterochromatic visual search. Journal of Vision 2003;3(12):68. doi: 10.1167/3.12.68.
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Many previous studies have revealed chromatic characteristics of visual search using relatively simple stimuli. They suggest that the color difference between a target and distractors is a dominant factor, however, it might not be applicable to color search which consists of various distractors.
Yokoi and Uchikawa (2001) investigated the chromatic characteristics using heterochromatic stimuli with various chromaticities. Although the relative color differences among distractors were kept constant, search time was varied according to the absolute chromaticities. We proposed the categorical color search model in which stimuli were assumed to be classified instantaneously by their basic color categories, and search time should depend on the number of stimuli in the segregated target color category.
To test this hypothesis quantitatively, two experiments were designed. In Experiment 1, 12 disks were displayed briefly (200ms) with a target cue. Disks were chosen to construct a spherical structure in the OSA UCS, so that color differences were constant in all conditions. Color categories of disks were identified by categorical color naming. Results showed that the fewer a number of stimuli in the same category as the target was, the higher the detection probability became.
In Experiment 2, a distractor set consisted of 13 chromaticites which constructed a sphere in the OSA UCS. A target was located outside of the sphere. The number of distractors for each chromaticities were 5, 7, and 9 disks, so that total set-sizes were 66, 92, and 118 respectively. Search time to detect a target disk which was shown for 1s prior to search, was measured. Results showed that search time did not depend on the total set-sizes, but on the number of disks in the same category as the target. Both results suggest that, as our model predicted, heterochromatic visual search is mediated by the categorical color mechanism.
YokoiK.UchikawaK.(2001). Categorical color perception influences heterochromatic visual search [Abstract]. Journal of Vision, 1(3), 116a, http://journalofvision.org/1/3/116, DOI 10.1167/1.3.116.
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