Retention of symbolic communications skills by severely mentally retarded persons.

The nonspeech symbol vocabularies of five severely mentally retarded persons were assessed 18 months after the completion of a longitudinal computer-keyboard symbol acquisition study. These individuals retained a mean of 83% of their comprehension vocabularies and 70% of their production vocabularies without systematic maintenance teaching on the learned symbols. Interviews with special-education and living unit staff members corroborated this result and described the ways in which the subjects used their conversation boards in their everyday environment.