When the person is functioning within ACL 4 Low, memory aids must only allow one course of action and be very easy to follow. Written signs and instructions are likely to be ignored. Memory aids like an automatic pill dispenser which has an audible alarm and flashing light that does not switch off until the person tips the pill dispenser have more chance of success. Perimeter alarms and smoke detectors with carers directing the person is what is required for someone who is unable to store information in their working memory.