Clock drawing is sensitive to executive control: a comparison of six methods.

We examined six clock-drawing task (CDT) scoring systems relative to the Executive Interview (EXIT25, a measure of Executive Control Function [ECF]) and the Mini-Mental State Exam (MMSE). Subjects included n = 33 National Institute of Neurological, Communicative Disorders, and Stroke "probable" Alzheimer's disease (AD) cases and n = 52 independent living controls. AD cases and controls differed on the EXIT25, MMSE, and all CDTs. All CDTs were significantly correlated with the EXIT25 (ranging from r = .56 to r = .78). These associations generally persisted after adjusting for Age, Education, and MMSE scores. In backwards stepwise linear multivariate regression models, only CLOX: An Executive Clock-Drawing Task scores contribute significantly to EXIT25 scores (R2 = .68) and MMSE scores (R2 = .72). Clock drawing draws upon both executive and general cognitive resources. CLOX explains incrementally more variance in ECF than other CDTs.