Coffee with jelly or unbuttered toast: Commissions and omissions are dissociable aspects of everyday action impairment in Alzheimer's disease

Relative to our understanding of the memory and language deficits associated with Alzheimer's disease (AD), little is known about problems with everyday action performance (i.e., meal preparation, grooming). The resource theory proposes that everyday action problems are best explained by a unitary deficit in general cognitive resources. However, recent research suggests that omission and commission errors may reflect dissociable aspects of action impairment, with only omissions associated with resource limitations. This study examined everyday action performance in 70 participants with AD who also underwent a neuropsychological evaluation. First, correlation and principal component analyses were performed to examine the construct(s) that might explain everyday action impairment. Second, relations between everyday task component(s) and neuropsychological tests were examined by using correlation and regression analyses. Third, differences in everyday action error patterns were examined among participants of comparable overall impairment levels. Results showed omission and commission errors were uncorrelated and distinct components of everyday action performance, predicted by different neuropsychological tests, and differentially distributed even among participants with comparable overall impairment.