Young and elderly participants, and participants with Alzheimer's disease (AD) were compared via the suffix paradigm, where a not-to-be-recalled item is appended onto sequences to be immediately recalled. This task was followed by delayed tasks. In immediate recall, AD subjects showed both extralist and suffix intrusions. Recall of auditorily as compared with visually presented stimuli was superior, with the difference increasing in older subjects. The auditory but not the visual suffix produced an end-of-sequence decrement, which was greater in AD than in other groups. After delay, the elderly and young showed virtually perfect performance. The AD participants showed relatively high performance; however, extralist intrusions were frequent, resulting in a relatively low hit rate. As in immediate recall, intrusions showed specificity for AD, and in this paradigm appeared to be a marker differentiating AD and normal subjects. However, the sample size limits the power and generalizability of these findings.

Potential age differences in selective attention and response inhibition in 16 young and 16 elderly college students were explored using the stimulus suffix paradigm. Subjects were presented with auditory and visual lists of seven-letter sequences. Half the lists were appended with a letter suffix that was not to be recalled. Recall was spoken and written and in strict serial order. Despite similar letter spans, serial recall was more difficult for the elderly than for the young. Final-item recall advantage in the control condition was reduced more for the elderly than for the young in the auditory modality, and the elderly were more susceptible to a small degree of visual suffix interference. Older subjects made more suffix and extralist intrusion errors than did young subjects. Oral recall, along with the method of recording written responses, may have allowed these errors to surface. The extralist intrusion errors were phonological or based on alphabetic order, suggesting that the elderly may experience task-competitive, internally generated noise, which enters the response set. The suffix intrusions, along with greater susceptibility to the suffix, suggest an attentional type of deficit related to ineffective response inhibition in the elderly.

Research has shown that elderly as compared with young adults show relative deficits both in processing visually as compared with auditorily presented stimuli and in tasks having attentional components. In this study, visual and auditory presentation was compared in young and elderly adults using the suffix paradigm in which the control condition involves immediate serial recall and the experimental condition, a suffix, a not-to-be-remembered final item. The standard finding in this paradigm is called the modality effect, superior auditory as compared with visual performance in the control condition which is localized at the end of the sequence. Generally, auditory suffixes following auditory sequences reduce the modality effect while visual suffixes following visual sequences do not. The results showed generally standard modality and suffix effects for both age groups. Relatively inferior performance was present in the elderly in the visual as compared with the auditory control conditions suggesting recoding deficits in this group. Auditory suffixes following auditory sequences had a relatively greater performance effect on the elderly than the young, while visual suffixes following visual sequences did not impair the performance of either group. This suggests a modality specific attentional deficit in the elderly. Rank order correlations suggest that individuals within both age groups showing large differences in performance between auditory and visual control conditions may have relative recoding difficulties for their age. Additionally, increased susceptibility to auditory interference for elderly as compared with young subjects may be a marker of aging, while relative within-group susceptibility to auditory interference may be a deficit on the part of young subjects.