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Krystal A. Cunningham, Bosco S. Tjan; Spatial arrangement of irrelevant color in visual search. Journal of Vision 2005;5(8):278. doi: 10.1167/5.8.278.
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© ARVO (1962-2015); The Authors (2016-present)
The colors of nearby regions in natural scenes tend to be similar. The purpose of this study was to determine if visual-search performance could be affected by the spatial arrangement of color when color is not a relevant feature.
The task consisted of searching for a vertical Gabor among oblique ones tilted at 15 deg clockwise against a gray background. Spatial distribution of color was manipulated in 3 conditions. In the “random” condition, the Gabors were randomly assigned to be red or green with matched luminance. In the “cluster” condition, an imaginary line divided the display vertically in half; the Gabors were red in one half and green in the other half. In the “uniform” condition, all Gabors were either red or green. Set sizes were 2, 8, 14 and 20.
The mean accuracy of 9 Ss was 95%. Log transformed RTs of the correct trials were subjected to ANOVA. Spatial distribution of color (COLOR) had a main effect on RT, in that the random condition led to significantly longer RTs (p < .05), but no difference was found between the cluster and uniform conditions (p=.704). There was an interaction between COLOR and TARGET (present or absent), with COLOR having a greater impact on RT for target-absent trials. There was also an interaction between COLOR and SETSIZE. The average search slopes were 127 (random), 98 (cluster), and 107 (uniform) ms/item for target-absent trials, and 55, 52, and 54 ms/item, respectively, for target-present trials.
Overall, random spatial arrangement of color, as opposed to uniform color or clusters of uniform colors, significantly increased search time, in terms of both setup time and search slope. The effect was disproportionally large when the target was absent. It appears that spatial discontinuity of color receives obligatory processing that disrupts visual search both at the onset and during the search.
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