Aging, perception, and visual short-term memory for luminance-defined form.

The sensory, perceptual, and visual short-term memory (VSTM) capacity of young and older observers for processing luminance-defined shape information was assessed in a series of experiments. The following were assessed: each individual's threshold necessary to detect a square from its background as measured by luminance thresholds; the capacity for making simultaneous size discriminations when compensating for individual differences in sensory input; the capacity for making sequential size discriminations; and the capacity for remembering size differences over time. The results show a selective deficit for simultaneous perceptual processing for older subjects, which cannot be attributed to differences in sensory input, task difficulty, interhemispheric transfer, or VSTM.