Manual communication and mental retardation: a review of research and implications.

The use of manual communication systems with individuals classified as mentally retarded is increasing; the extent to which that therapy is guided by systematic practices and principles was investigated. An analysis of the research literature suggested that a variety of sign systems have been used with retarded individuals of varying ages. The application or success or failure of that therapy does not seem to be determined by a particular treatment model and/or set of guidelines. Implications for development of language-training programs were discussed.