Age, clutter, and competitive selection.

Modern theory explains visual selective attention as a competition for receptive fields in the extrastriate cortex. The present study examined whether this competition contributes to older adults' difficulty in processing visual clutter. In 2 experiments, young and older adult subjects made same-different judgments of target shapes in displays with or without clutter. The target shapes were either high or low in discriminability. The spatial separation between targets varied across trials, and the effects of competitive selection were gauged through decrements in task performance that resulted as separation decreased. Both age groups showed a competition-in-clutter effect, evincing a stronger influence of target separation within cluttered displays. However, the costs of clutter in general and the strength of the competition-in-clutter effect more specifically were both substantially larger for older adults. Effects of clutter and competition also varied with stimulus discriminability; judgments of highly discriminable stimuli evinced no intertarget competition in uncluttered displays for either age group, while judgments of less discriminable stimuli showed competition whether clutter was present or not. Results suggest that clutter disproportionately degrades older adults' visual performance by forcing more careful stimulus resolution, engendering stronger competition for selection.