When metacognition fails: impaired awareness of deficit in Alzheimer's disease.

Two new measures were developed to assess quantitatively the degree to which patients with Alzheimer's disease (AD) are aware of their memory deficit, and to evaluate the relation between dementia severity and awareness of deficit. Results of a questionnaire measure indicated that AD patients rated their own difficulties with cognitive activities of daily life significantly lower than relatives rated patients' problems, and this discrepancy was related to patients' dementia severity. On another measure involving task performance predictions, AD patients were inaccurate in predicting their performance on most cognitive tasks when compared to both their actual performance and relatives' predictions, despite generally accurate prediction of their relatives' performance on the same tasks. These results are discussed in terms of a breakdown in metacognitive processes.