Manipulation of stimulus features in vocational-skill training of severely retarded individuals.

Fifty-one severely retarded adults were taught a difficult visual discrimination in an assembly task by one of three training techniques: (a) adding and reducing large cue differences on the relevant-shape dimension; (b) adding and fading a redundant-color dimension; or (c) a combination of the two techniques. There were significant differences between training conditions in both trials- and errors-to-criterion performance. These were attributed to differential establishment of stimulus control in the first phase of training, with the combined procedure being the most effective, the color coding/fading next, and the relevant-dimension cue-disparity method the least powerful. These results demonstrated that substantial differences may exist in the efficacy of various vocational-skill training procedures involving manipulation of stimulus features.