Validation therapy was developed by Naomi Feil between 1963 and 1980 for older people with cognitive impairments. Initially, this did not include those with organically-based dementia, but the approach has subsequently been applied in work with people who have a dementia diagnosis. Feil's own approach classifies individuals with cognitive impairment as having one of four stages in a continuum of dementia: these stages are Mal orientation, Time Confusion, Repetitive Motion and Vegetation. The therapy is based on the general principle of validation, the acceptance of the reality and personal truth of another's experience, and incorporates a range of specific techniques. Validation therapy has attracted a good deal of criticism from researchers who dispute the evidence for some of the beliefs and values of validation therapy, and the appropriateness of the techniques. Feil, however, argues strongly for the effectiveness of validation therapy.