The obsolete identity connected to a cognitive disability sustains their oblivion to the reduction in their cognitive abilities. What they can say about themselves often sounds better than what they can do. Self-reports are the primary method of gaining information about a person in doctor's offices, case management and legal proceedings. Self-reports usually contain information about the quality of their life before the onset of a cognitive disability, and decisions about their current life are incorrect.
The alternative is to gather information from a reliable person who has observed their current pattern of activity performance. The person who lives with them may or may not be reliable.