Behavioral slowing with age: boundary conditions of the generalized slowing model.

One hundred and twenty-two adults ranging in age from 20 to 83 years participated in this study of visual discrimination and recognition. The simultaneous-matching-to-sample (discrimination) and delayed-matching-to-sample (recognition) paradigms used identical stimuli for spatial frequency, luminance, spatial localization, orientation, pattern, trajectory, and velocity matching. Linear regression analyses indicated that increased age slowed reaction time on the simultaneous-matching tasks. This relationship was not found, however, when subjects were required to match the stimuli after a delay. When older adults' reaction times were regressed on those of adults in their 20s, very different patterns of age-related slowing emerged from the data as a function of task requirements. The results from the simultaneous-matching paradigm replicate previous reports of general slowing on nonlexical tasks, but this was not true for the results from the delayed-matching paradigm, which used similar stimuli but also involved short-term memory.