Operant conditioning procedures were used to establish a generative use of the plural morpheme in the speech of a severely retarded girl. During training trials, reinforcement was presented contingent upon correct imitation of singular and plural verbalizations by the experimenter, in response to objects presented to the subject singly and in pairs. A generative productive plural usage resulted, the girl correctly labeling new objects in the singular or plural without further direct training relevant to those objects. After establishing the singular/plural usage, the contingencies were reversed (reinforcement of plural responses to single objects, and vice-versa). This produced a corresponding reversal of response by the child. The original usage was then recovered by returning to the previous contingencies. A second experiment analyzed certain error responses occurring during the first experiment, and further probed the generative nature of the subject's plural usage. It was found that errors were somewhat more likely to occur in the pluralization of words ending in vowels than of words ending in consonants. Furthermore, several words whose plurals had been learned according to the reversed plural rule, when examined later during reinforcement of normal plural usage, were found then to exemplify the normal rule being reinforced, yet without direct training.

A technique of controlling undesirable or disruptive behavior during an ongoing program of verbal training with a retardate is described. The technique required that the stimulus materials of the verbal training program be graded according to difficulty, i.e., in terms of the length and complexity of the stimulus materials. (This resulted in an initial grading of the stimulus materials into different levels of probability of reinforcement.) Changes by the experimenter from high-difficulty to low-difficulty stimuli for two trials contingent upon disruptive behavior increased the rate of that behavior; changes from low-difficulty to high-difficulty stimuli for two trials contingent upon disruptive behavior decreased its rate. Thus, contingent alternation of the stimulus materials of the ongoing training program controlled the frequency of undesirable behaviors within the experimental sessions. This technique may comprise an alternative to other procedures which require punishment or timeout from the ongoing program.

No abstract