Spoken and signed naming of foods after receptive exclusion training in severe retardation

Two low-functioning mentally retarded subjects learned to name food items after receptive exclusion training, conducted as follows: The subjects first learned to select a small number of foods in a two-choice matching-to-sample task. For one subject, the samples were dictated names; for the other, the samples were manual signs. They also learned to name these "known" foods, either orally or by signing. On exclusion trials, a known food was displayed with a new food whose corresponding name or sign had not yet been learned, and a novel sample (spoken or signed), corresponding to the new food, was presented. The subjects typically selected the new food immediately, apparently by "excluding" the food related to the known sample. If a known sample was presented, however, the subjects continued to select the known food correctly. Periodically during exclusion training with a number of new foods, the subjects were tested for production of food names or signs. With few exceptions, the subjects produced the food names without direct training, often after only a few receptive exclusion trials. The results suggest strategies for teaching simple receptive and expressive relations to severely mentally retarded individuals.