| The ability to use the eyes and visuospatial attention to search for specific items in cluttered space declines in aging (Plude & Doussard-Roosevelt, 1980; Oken, Kishiyama & Kaye,1994; Foster, Behrman & Stuss,1995). This skill has been reified experimentally as visual search---the selection of goal-relevant visual stimuli embedded in distractions without overloading limited capacity attentional systems (Kahneman, 1973). The goal of the present study was to understand the basis of age-related deficits in the ability to use both the eyes and visuospatial attention in the course of visual search in a complex visual scene. In comparison to young adults, older adults were hypothesized to exhibit (a) both a constriction in the range of the attentional focus (Chavez, 2001; Gottlob & Madden, 1999) and reduction in attentional enhancement benefits at the presumed center of the attentional focus (Chavez, 2001) and (b) an increase in the number of saccadic eye movements executed (Scialfa et al., 1994) related to the age-related constriction of the attentional focus and need to foveate peripheral stimuli. The consequences of age-related changes on the distribution of attention and how that in turn affects the attention/saccadic eye movement relationship in visual search were investigated using measurements of saccadic eye movements, RT, and P(A) (Green & Swets, 1966).; Results from 4 experiments on the role of attention and saccades in visual search showed that: (a) in young adults the attentional focus is distributed as a gradient, while in older adults the attentional focus is diffusely distributed but varies with task demands and stimulus characteristics; (b) in older adults attentional enhancement at the presumed locus of attention is reduced; (c) in young adults, sensitivity and RT along with saccadic eye movements varied with cue-target distance suggesting attentional guidance of saccade execution, but in older adults, the effect of cue-target distance on saccadic eye movements and both RT and sensitivity was absent suggesting age-related weakening of the relationship between attention and eye movements in visual search. Additionally, related to the finding that attentional enhancement is weakened at the locus of attention, results of Experiment 2 suggest that the scaling of attention is slowed in aging (Greenwood & Parasuraman, 1999). Findings were discussed in terms of Greenwood and Parasuraman's model of search (1999; 2004). |
