Verbal fluency in senile dementia: an analysis of search and knowledge.

This investigation concerns the ability to decide on superordinate category membership as a determinant of retrieval failure in fluency tasks. Subjects were 24 normal elderly (mean age 83) and 66 senile dementia patients (mean age 80.5). Two tasks were presented. In the recall task subjects were asked to supply instances of articles of clothing and fruits. In a recognition task subjects were tested for their knowledge of category membership. Normative production frequencies of the items in the recognition task were systematically varied from intermediate to very low. Senile dementia patients generated significantly (P less than 0.001) less instances of both categories than normal elderly. In contrast, recognition of category exemplars was not impaired. These results present direct evidence for the hypothesis that senile dementia patients know far more category instances than they are able to produce.