Age, sex, and hemisphrere asymmetry differences induced by a concurrent memory processing task.

Subjects in three age groups matched simultaneously presented pairs of visual words or geometric shape stimuli as belonging in a "same" or "different" category. No age effects were observed unless subjects were also required to repeat the sequence of the last three "same-different" responses immediately following each trial. Cerebral asymmetry effects were expected for the word and shape dimensions, but were not observed. Asymmetry effects for the same-different dimensions were noted and allowed inference regarding serial and parallel processing effects. When required to repeat the sequence of past responses following each trial, older males showed an increase in time to make the same judgments. Older females showed increased right vs left visual field processing times when required to repeat the sequence of same-different responses following each trial.