Scale of attentional focus in visual search

The effects of the spatial scale of attention on feature and conjunction se arch were examined in two experiments. Adult participants in three age grou ps-young, young-old, and old-old-were given precues of varying validity and precision in indicating the location of a target letter subsequently prese nted in a visual array. Systematic decreases in the size of a valid precue (toward the size of the target) progressively facilitated both feature and conjunction search, with a greater benefit accruing to conjunction search. Age-related slowing in conjunction search was mitigated by precise (small a nd valid) precues, presumably because they reduced the need for participant s in the young-old group to focus and to shift attention. Nevertheless, thi s benefit was reduced in the old-old group. The effects of valid location p recue size varied with cue-target stimulus onset asynchrony (SOA) in a mann er that interacted with search difficulty: Effects of cue size developed mo re rapidly in feature search but more slowly in conjunction search. Finally , when precues were invalid for target location, search was faster with lar ger sized precues. Thus, in both easy feature search and hard conjunction s earch, the scale of visuospatial attention modulates the speed of visual se arch. Furthermore, when the SOA is sufficiently long for cue effects to dev elop, the ability to dynamically adjust the scale of visuospatial attention appears to de cline in advanced age. These results go beyond current model s in suggesting that visuospatial attention possesses two dynamic propertie s-shifting in space and varying in scale-that are deployed independently, d epending on task demands.