ON AGE-DIFFERENCES IN PROCESSING VARIABILITY AND SCANNING SPEED

This investigation examined adult age differences on a recognition memory task for order information. Experiment 1 consisted of a modified memory-scanning task in which a memory set of four letters was presented in boxes. Subjects judged whether a subsequent probe letter was or was not transposed from its original presentation position. One block of primary memory trials (i.e., no distractor task) and one block of secondary memory trials (i.e., a 10-second distractor task) were used. Experiment 2 used basically the same task, except both blocks of trials were primary memory tasks, and acoustic similarity was manipulated. A processing variability model predicted that both experiments should show distance effects (i.e., transposing letters a distance of one box should result in more errors and/or longer reaction times than a transposition of two, or three boxes) for both right and left transposition directions. However, a generalized slowing model predicted that distance effects should only occur for left transpositions (because of left-to-right scanning order). The present data supported the processing variability model but not the generalized slowing model.