Age-related differences in serial binary classification

In a two-choice serial task, three groups of subjects with median ages of 37, 54, and 69 years pressed one response lever when the current signal was the same as its immediate predecessor in a sequence, and the other when it was not. Four classes of events-same signal/same response, same signal/different response, different signal/same response, different signal/different response-occurred equally often. The reaction times of subjects in the oldest group exceeded those of the two younger groups by a constant amount under all conditions; there was no evidence that stimulus or response repetition interacted with age. The data from all age groups support only the hypothesis that repeating a given signal is sufficient to produce the repetition effect in a choice reaction task.