On age differences in processing variability and scanning speed

Research indicates that ''internal noise'' may be responsible for the age differences found in performance on many memory and perceptual tasks. The internal noise hypothesis proposes that older adults have a loss of processing resolution whereby target stimuli (the items to be remembered) are not as easily distinguished from background, or nontarget stimuli. When we view a list, for instance, the order of the list is stored in memory. But as we age, according to internal noise hypothesis, it is probable that the positions of individual items on the list will drift, or background items will be recalled instead. The theory also holds that as a function of where the item was originally stored in memory, an item's familiarity decreases the further away it gets from where its original position. In the present investigation, two experiments were performed to examine adult age differences on a recognition memory task for item order. In experiment one, which tested processing variability, subjects saw four letters and they were asked if a subsequent probe letter was in its original position or in another position relative to the other letters. They were tested both immediately and after a 10-second distractor task. Experiment two was virtually the same, except acoustic memory was tested and there was no distractor task. The internal noise hypothesis predicted that there should be distance effects, as described above, in both tasks resulting in more errors in recognition when letters were transposed. The data supported this hypothesis, as older adults exhibited higher levels of processing variability. (Consumer Summary produced by Reliance Medical Information, Inc.)