Dr. Förstl was impressed by Dr. Reisberg's data showing a close relationship between cognitive impairment and behavioral and psychological symptoms of dementia (BPSD). Yet he questioned Dr. Reisberg's conclusion that cognitive impairment is necessary for developing hallucinations or delusions. Dr. Reisberg responded that although there is no correlation between scores on the Mini-Mental State Examination (MMSE) and BPSD, it does not mean that cognition is not involved in these symptoms. By definition, BPSD are behavioral and psychological. There is a psychological, or cognitive, element to all BPSD, said Dr. Reisberg. As an example, he noted that a patient with cataracts is more likely to experience visual hallucinations. A person who is not cognitively impaired will be able to censor those experiences and not discuss them with others. Patients with dementia do not censor this information, and tell others about their visual hallucinations. Dr. Reisberg noted, however, that visual hallucinations among patients with Alzheimer's disease (AD) are not common, occurring in about 20% of patients, with a peak occurrence just before the final stages of the disease. Dr. Shah commented that BPSD in patients in the final stages of AD may be difficult to detect because techniques for identifying these symptoms in severely cognitively impaired patients are lacking.