Aging and memory for frequency of occurrence of novel, visual stimuli: direct and indirect measures.

Memory for frequency of occurrence typically is investigated using familiar stimuli (e.g., words) and with "direct" tests of memory; that is, the subject is required to state explicitly how often an item occurred or which item occurred more often. Experiments 1 and 2 examined the effects of age on the ability to make judgments (i.e., direct tests) regarding the frequency of occurrence of words and of novel, visual stimuli (Japanese ideograms). In Experiment 3, young and old subjects were compared on "indirect" measures of memory for frequency of occurrence of these ideograms, as indexed by the mere exposure effect. On the direct test of memory, elderly and young subjects did not differ when shown words, but elderly were impaired compared with young subjects when ideograms were presented. When tested indirectly, both groups were sensitive to the frequency of occurrence of ideograms. The pattern of results replicates and extends previous findings regarding performance dissociations between direct and indirect measures of memory in aging.