A comparison of the effectiveness of graphic symbol and manual sign training with profoundly retarded children

Using a random-block design, 52 profoundly retarded nonverbal children were matched on relevant variables and randomly assigned to one of three treatment groups or a no-treatment group. In Phase One, two groups were trained in either the Premack or NON-SLIP graphic systems. Children in the Premack group learned an average of 2.3 symbols; no child in the NON-SLIP group reached the symbol stage. In Phase Two, these two groups and a third group were taught manual signs from an American Sign Language lexicon. There were significant differences in IQ and language age from pre- to posttest, and children in the two groups exposed to both graphic symbols and signs learned significantly more signs than graphic symbols. Signing appears to be a demonstrably superior intervention for profoundly retarded nonverbal populations.