Aging and feature search: the effect of search area.

The preattentive system involves the rapid parallel processing of visual information in the visual scene so that attention can be directed to meaningful objects and locations in the environment. This study used the feature search methodology to examine whether there are aging-related deficits in parallel-processing capabilities when older adults are required to visually search a large area of the visual field. Like young subjects, older subjects displayed flat, near-zero slopes for the Reaction Time x Set Size function when searching over a broad area (30 degrees radius) of the visual field, implying parallel processing of the visual display. These same older subjects exhibited impairment in another task, also dependent on parallel processing, performed over the same broad field area; this task, called the useful field of view test, has more complex task demands. Results imply that aging-related breakdowns of parallel processing over a large visual field area are not likely to emerge when required responses are simple, there is only one task to perform, and there is no limitation on visual inspection time.

Aging and spatial localization during feature search.

BACKGROUND: Previous studies indicate that older adults, like young adults, can efficiently search for a briefly presented visual target defined by a single salient feature presented amidst background distractors. However, little is known about older adults' ability to identify the spatial location of targets during this aspect of preattentive processing. OBJECTIVE: This study examined the extent to which older adults exhibit localization problems during feature search for a target with high conspicuity. Their performance was compared to that of younger adults. METHODS: Twenty older adults (mean age 70 years, 8 men and 12 women) and 20 younger adults (mean age 25 years, 6 men and 14 women) with good central and peripheral vision were tested. Subjects were asked to indicate via a computerized touch-screen the location of a briefly presented (80 ms) target presented amidst distracting stimuli (set size 8, 16, or 32). Targets were presented at either 10 degrees, 20 degrees, or 30 degrees eccentricity. The dependent measures were percent correct localization and, for trials in which there were errors, the spatial magnitude of the error. RESULT: Compared to young adults, older adults committed more localization errors during feature search, a problem which was accentuated with increasing target eccentricity. In addition, older adults' mislocalizations deviated from the correct location by greater distances. CONCLUSIONS: Older adults have spatial localization problems in preattentive processing during feature search, which could be detrimental to the guidance and deployment of visual attention.