Use of the alternating treatments design as a strategy for empirically determining language training approaches with mentally retarded children.

The present study was conducted as a practical demonstration of the potential utility of the alternating treatments design (ATD) in determining the most efficacious language training approach with mentally retarded children. Two subjects were chosen who used single words to communicate but who did not combine words to form sentences. Two sentence triads consisting of four words each and rated as equivalent in difficulty were trained. Each triad had one sentence trained using oral speech methods, a second trained using total communication methods, and a third sentence trained using a "modified" total communication approach. Each training procedure involved chaining sentence parts, reinforcement, and prompting. Oral methods involved presenting vocal stimuli and requiring vocal responses. Total communication methods involved presenting vocal and signed stimuli and requiring vocal and signed responses. The "modified" total communication approach also involved presenting vocal and signed stimuli, but required only vocal responses. For the initial sentence triad with each child, an alternating treatments design was used to determine the relative efficacy of the three language training methods. This approach was repeated with a second sentence triad for each child using a multiprobe technique within a multiple baseline design. Results were consistent within each subject but differed across subjects, with one child benefitting most from total communication methods and the other benefitting most from oral speech methods. Results were discussed in terms of the utility of the alternating treatments design as a potentially useful aid to traditional decision-making in the selection of language training strategies commonly employed with mentally retarded children.