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Lyndsey K. Lanagan, Elisabeth M. Fine, Peggy Chen, Cathleen M. Moore; Standing out in a crowd: Item discriminability increases attentional resolution. Journal of Vision 2005;5(8):1004. doi: 10.1167/5.8.1004.
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Background: Intriligator and Cavanagh (2001) reported that it is difficult to walk one's attention through densely crowded arrays of similar items. Here we test the hypothesis that it is less difficult to do so when the items within the array differ from each other. Methods: Observers walked through arrays of discs that were presented at 11.8 deg eccentricity. The discs were all the same color (gray) or differed in color. Density was 9, 13, 17 or 25 items in each hemifield. Observers walked their attention through the arrays in response to tones that were presented every 750 msec. Walk distances were 0, 5, 7, and 9 steps. A change in tone indicated the end of the walk, at which point the discs (whether gray or colored) changed color. The task was to report the color of the attended disc at the end of the walk. Results: For the 0-step condition, accuracy varied as a function of density, ranging from 92% in the density-9 condition to 54% in the density-25 condition; there was little difference, however, between the gray and the colored conditions (both 79%). For the attentional-walk conditions, performance was better in the colored condition than in the gray condition (60 vs. 52%, averaging across the 5-, 7-, and 9-step conditions). However, this effect was driven entirely by the two intermediate density conditions (density-13 and density-17). When the task was quite easy (density-9) or quite difficult (density-25) accuracy did not differ across gray and colored conditions. Conclusions: Attentional walks within a differentiated display appear to be easier than attentional walks within a homogenous display. The decline in performance in the 0-step condition suggests that observers have difficulty not just moving their attention among closely-spaced items, but moving their attention to a single item within similarly dense displays. An explanation of how these two factors interact requires further research.
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