Informal conversations are more productive than standardized interviews and need to be adapted per cognitive level.
When the person cannot talk or talk very little, a family member or a friend may be used to obtain reliable information.
People functioning within ACL 4 and 5 can talk and tell you about their history in doing activities. Educational and work histories are safe places to start an interview. When the person is functioning at ACL 3 and below, an observation of their activities will be a more productive use of your time.