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Abstract We report on the spoken language of 48 patients with dementia of the Alzheimer's type (DAT) who were divided into three approximately equal subgroups on the basis of the Mini-Mental State Examination (minimal 24–29, mild 17–23, and moderate 3–16) and 18 matched controls. The Cookie Theft picture description task from the Boston Diagnostic Aphasia Examination was chosen because it is considered an ecologically valid approximation to spontaneous discourse. All subjects were also assessed on a battery of semantic memory and non-verbal tests. Our analysis of the discourse sample focused on quantity versus information content over time, and included measures of the total number of syllables produced, the total number of information units produced, and the total time taken to describe the picture. We found that the total number of information-carrying units was the most salient variable which differentiated controls from even the minimal DAT subgroup. Moreover, information content correlated significantly with measures of lexico-semantic processing, but not with performance on non-linguistically based tests.
Giles et al. (1996) studied this question.