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The relative importance of potential and actual shocks in making shock situations function as negative reinforcers was studied. Shocks were scheduled to occur at the same rate during two stimuli. During one, squirrel monkeys could avoid the shocks; during the other, they were unavoidable. For the two stimuli the potential rate of shocks was the same, but the actual rate was lower during avoidance because of avoidance responding. Fixed‐ratio responding was maintained by the change from unavoidable shock to avoidance, indicating that the change was reinforcing when it resulted in a reduction in actual shock rate with no reduction in potential shock rate. Further increases in the rate of potential shock during avoidance had little effect upon the fixed‐ratio responding until the rate was increased to the point that the actual shock rate during avoidance was comparable with that during unavoidable shock. At that point, the fixed‐ratio response rate decreased nearly to zero. These findings show that actual shocks are more important than potential shocks in determining whether or not a shock situation will function as a negative reinforcer; this explains why the change from unavoidable shock to avoidable shock is reinforcing.

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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 model presented English words to three preschool children and reinforced accurate imitation of these words. The model also presented novel Russian words but the subjects' imitation of these words was never reinforced. As long as the subjects' imitation of English words was reinforced, their accuracy of imitating non‐reinforced Russian words increased. When reinforcement was not contingent upon imitation of English words, accuracy of imitating both the English and the Russian words decreased. These results support and extend previous work on imitation.

This report describes several primate environments in which two or more animals shared a common social area. Automatic programming was used to permit concurrent individual sessions. Some of the behavioral phenomena observed in these environments, including reinforcing properties of social interactions, are discussed.

Most children who learned to discriminate opposing 45° line tilts on a relational basis—oddity —did not learn the specific direction of the positive tilt. Most children who did not use oddity did discriminate the specific tilt.

An observational system, which has been developed to facilitate recording of the total behavioral repertoire of autistic children, involves time‐sampling recording of behavior with the help of a common Stenograph machine. Categories which exhausted all behavior were defined. Each category corresponded with a designated key on the Stenograph machine. The observer depressed one key at each 1‐sec interval. The observer was paced by audible beats from a metronome. A naive observer can be used with this method. The observer is not mechanically limited and a minimum of observer training is required to obtain reliable measures. The data sampled during a five‐week observation period indicated the stability of a taxonomic instrument of behavior based upon direct, time‐sampling observations and the stability of spontaneous autistic behavior. Results showed that the behavior of the subjects was largely nonrandom and unsocialized in character.

A group of 12 children were enrolled in a preschool class. During the first experimental stage they participated in special events contingent on token earning. Tokens were acquired by engaging in a variety of study behaviors. After a level of study behavior was established under this contingency, the special events were provided noncontingently. Study behavior declined throughout the noncontingent stage. Reestablishing the original contingencies produced an immediate return to the initial level of study behavior. Noncontingent special events reduced the amount of independent study, group participation, and cooperative study. The study behavior of each child was altered in the same direction, though differences in the magnitude of effects from child to child were observed.