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Tammy Menneer, Doug J Barrett, Luke Phillips, Nick Donnelly, Kyle R Cave; The breakdown of efficient search when either of two colour targets can appear. Journal of Vision 2003;3(9):568. doi: https://doi.org/10.1167/3.9.568.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose. In visual search tasks, single target searches are most efficient when the target can be discriminated from other items in the display by differences within a single feature dimension. We investigate whether this efficiency is maintained when either of two targets specified by differences within a single feature dimension can appear. Method. Participants responded to the presence or absence of a specified color target in displays of eight heterogeneous color patches. Three separate searches were carried out, with participants searching for (i) color A, (ii) color B, or (iii) color A or B. The order of presentation was counterbalanced, and exposure thresholds for 71% correct performance were determined using a two up one down staircase procedure for single and multiple target searches (N=37). Results. Exposure thresholds in the A or B condition significantly exceeded the summed thresholds for conditions A and B. Identical search conditions using complex shapes, however, produced a different pattern of results with exposure thresholds for the A or B condition being statistically equivalent to the summed thresholds for conditions A and B. Conclusion. Searching simultaneously for either of two color-targets is very inefficient compared to searching for a single color-target. This suggests that guided search is possible for a single color-target but not for a single complex shape target, or for multiple color-targets when these are not linearly separable in color space from other items in the display.
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