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R. L. Carlson, S. Shomstein; Disambiguating strategic effects in visual search. Journal of Vision 2001;1(3):119. doi: 10.1167/1.3.119.
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Wolfe, O'Neill & Bennett (1998) propose an attentional account for eccentricity effects (e.g., Carrasco, Evert, Chang & Katz, 1995). According to their proposal, central items of a search array should be searched first. However, we examined this issue in closer detail by separating the point of fixation from the center of the search array. Employing a variation of the basic design used by Wolfe et al., we asked observers to search for a target (colored bar of a particular orientation) among distractors (bars that differed from the target along one dimension), such that the entire search array appeared in one of four quadrants. With this design, the center of the search array is offset from the point of initial fixation. This allows for a distinction to be made between the attentional strategy of searching from the center of the array (as claimed by Wolfe et al.) and that of a bias (perceptual or attentional) resulting from the point of initial fixation. Our results indicate that items closer to fixation are searched first, even though fixation is never the central point of the array. This approach of systematically varying the relationship between the locus of attention, the point of fixation, and the position and shape of the search array is likely to prove fruitful in understanding strategic contributions to search performance.
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