Naturalistic action impairments in dementia.

Naturalistic actions are everyday tasks (e.g. cooking) that require one to use multiple objects and sequence steps to achieve a goal. Naturalistic action impairment has been attributed to executive dysfunction [Higher cortical functions in man. New York: Basic Books, 1966], semantic knowledge degradation [Brain 111 (1988) 1173], and, more recently, general limitations in cognitive resources [Neuropsychology 12 (1998) 13]. Action impairments were explored in 51 dementia participants with the short form of the multi-level action test (MLAT-S). A clinical neuropsychological test protocol was also administered. Regression analyses including measures of executive functioning, semantic knowledge, and global cognitive functioning showed that global cognitive functioning was the best predictor of MLAT-S errors. Furthermore, task demands significantly influenced the type and frequency of errors, and dementia participants showed a pattern of errors similar to that reported in other clinical populations [Cognitive Neuropsychology 15 (1998) 617; Neuropsychologia 37 (1999) 51; Neuropsychology 12 (1998) 13]. Taken together, the present findings are inconsistent with semantic and executive accounts, but support the limited-capacity resource theory of naturalistic action impairment.