Aging and similarity grouping in visual search.

It has been argued that principles of perceptual organization play an important role in the representation of a visual stimulus and that elderly adults may be deficient in perceptual unit formation. The present study examined the extent to which the Gestalt principles of grouping by proximity and similarity predicted the formation of large perceptual units that could affect performance in a visual search task. The verbal reaction time to determine the presence or absence of a target letter in arrays of 1, 5, or 9 elements was determined for young (20 years) and elderly (69 years) adults. Both age groups could take advantage of the organization implied by Gestalt principles in finding a target in the context of a small implied group. The elderly adults, however, were not able to organize a single perceptual unit composed of eight elements. Thus, although the visual search performance of the age groups was similar, the elderly adults did yield evidence of a perceptual organization deficit.