||The spatial resolution of visual attention.
Evaluated the grain of visual attention (Exp 1) and the minimum spacing at which attention can select individual items (Exp 2). In Exp 1, 8 Ss (aged 22-35 yrs) performed a computerized item tracking task at many viewing distances using either 4 targets items (TIs; 4 Ss), or 1 and 3 TIs (4 Ss). Results show that when the display subtended <1" in size, TI tracking was no longer possible because TIs could not be individuated. The limiting size for selection was roughly the same whether tracking 1 or 3 TIs. In Exp 2, 5 Ss (aged 22-35 yrs) performed an attention stepping task with dense, static displays. Results show that the critical spacing was about 50% coarser in the radial direction compared to the tangential direction and was coarser in the upper as opposed to the lower visual field. The results suggest that no more than about 60 TIs can be arrayed in the central 30" of the visual field while still allowing attentional access to each individually. The data show that selection has a coarse grain, much coarser than visual resolution. The authors conclude that the parietal area is the most likely locus of this selection mechanism and that it acts by pointing to the spatial or cortical coordinates of TIs rather than by holding a representation of the items themselves. (PsycINFO Database Record (c) 2007 APA, all rights reserved)