On which abilities are category- and letter-fluency grounded? A confirmatory factor analysis of 53 Alzheimer's patients

BACKGROUND/AIMS: In Alzheimer's dementia (AD), letter fluency is less impaired than category fluency. To check whether category fluency and letter fluency depend differently on semantics and attention, 53 mild AD patients were given animal and letter fluency tasks, two semantic tests (the Verbal Semantic Questionnaire and the BORB Association Match test), and two attentional tests (the Stroop Colour-Word Interference test and the Digit Cancellation test). METHODS: We conducted a LISREL confirmatory factor analysis to check the extent to which category fluency and letter fluency tasks were related to semantics and attention, viewed as latent variables. RESULTS: Both types of fluency tasks were related to the latent variable Semantics but not to the latent variable Attention. CONCLUSIONS: Our findings warn against interpreting the disproportionate impairment of AD patients on category and letter fluency as a contrast between semantics and attention.