Some analyses of forgetting of pictorial material in amnesic and demented patients.

Three experiments evaluating the rate of forgetting of pictorial stimuli in amnesic, demented, and normal control subjects are reported. When prolonged exposures of pictorial material were used to equate recognition performance after a 10-min delay, alcoholic Korsakoff (AK) patients and patients with Huntington's Disease (HD) demonstrated normal rates of forgetting over a 1-week period. In addition to replicating previous findings with AK patients, these results are consistent with recent suggestions that retrieval, not storage, deficiencies characterize the HD patients' memory problems. The second experiment explored whether the AK and HD patients learned as much about the features of the pictorial stimuli as did the normal subjects. After the subjects viewed a series of pictorial stimuli, recognition was assessed 10 min later using the whole pictures, isolated main features of the pictures, or isolated peripheral features of the pictures. The results showed that, with prolonged exposure times, the two patient groups did not differ from the normal control group in terms of the features of the stimuli they analyzed and remembered. The third experiment evaluated the rate of forgetting of pictorial material of two groups ("young" and "old") of normal subjects, one group ("old") having viewed each picture for 1 s and the other group ("young") for .5 s. Although the two groups did not differ in recognition performance 10 min after presentation, the young subjects who viewed each picture for .5 s showed more rapid forgetting over a 1-week period. This finding indicates that similar recognition scores do not necessarily signify equal learning under all exposure conditions.