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Retrieval from semantic memory, measured by tasks requiring subjects to name items from a given category, was studied in mild Alzheimer-type dementia (Mild-ATD) subjects, moderate-to-severe Alzheimer-type dementia (MS-ATD) subjects, and normal controls. Semantic retrieval performance was shown to be highly sensitive to both the presence and the severity of ATD. Retrieval from both semantic categories and letter categories showed differences in the rate of production of correct responses between subject groups. These rate differences were not due to differences in accessibility of low-dominance semantic category members or low-frequency letter category members. An increase in errors as well as a decrease in correct responses contributed to the performance deficits of the ATD subjects. Furthermore, the pattern of errors changed from Mild- to MS-ATD. Qualitative as well as quantitative differences were also observed in the performance of Mild- versus MS-ATD groups on a third type of semantic retrieval task--the supermarket task. As performance of the ATD subjects declined on these semantic retrieval tasks, so did their performance on other tasks assessing primarily attention, language, and memory. The findings are discussed in terms of the progressive breakdown in both attentional and semantic memory functions which are associated with ATD.

Tip-of-the-tongue (TOT) experiences were examined in 30 young (ages 18-24 years), 30 young-old (ages 60-74), and 30 old-old (ages 80-92) adults. In Study 1, TOT experiences were experimentally induced with definitions of to-be-retrieved targets. If the target was not retrieved, orthographic or semantic cues were provided. Age-related increases in the occurrence of TOT experiences and in the time needed to resolve TOT experiences were found for young versus young-old and young-old versus old-old groups; all comparisons were significant except for young versus young-old TOT occurrence, which approached significance. In Study 2, the same participants recorded naturally occurring TOT experiences in structured diaries during a 4-week interval. Both the number of TOT experiences and the resolution time for TOT experiences increased with age. However, the percentage of TOT experiences resolved was equal across age groups; given enough time, even the oldest participants resolved virtually all TOT experiences.