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Two retarded boys exhibited abnormally low rates of smiling. In Exp. I, the frequency of a boy's smiling was first increased with candy reinforcement, but the frequency of the response did not decrease when candy reinforcement was terminated. When the subject wore a sign designed to make social interactions contingent on not‐smiling, the frequency of smiling decreased. The sign was then changed to make social interactions contingent on smiling and the rate of smiling increased. In Exp. II, a second boy initially never smiled. Establishment of a contingency for candy reinforcement did not increase this zero response rate. Instructing the child to smile initially increased smiling, but the instructions then became progressively more ineffective. Candy reinforcement increased the rate of smiling to a normal range, but the rate of the response promptly decreased when this reinforcement was discontinued. Continuous candy reinforcement was again employed to increase the response rate and then progressively leaner schedules of variable‐ratio candy reinforcement were employed. Consequently, the rate of smiling did not decrease when candy reinforcement was again eliminated. Subsequently, signs were employed to regulate social interactions and the rate of smiling was shown to be controlled by these interactions serving as reinforcers.

The purpose of this investigation was to assess the effects on performance rate of simply writing the answers to mathematics problems versus verbalizing the problems before making a written response. The subject was an 11‐yr‐old boy whose response accuracy on mathematics problems was very erratic. Three experiments were conducted, each consisting of three phases. In each first phase, the subject was requested to write the answers to sets of mathematics problems. In the second, he was required to verbalize the problem before writing the answer. In the third phase, the subject was told to write the answer again without prior verbalization. The results indicated that the subject's correct answer rate increased and his error rate decreased as a result of his verbalizing the problems before making a written response. Results further revealed that in the final phase of each experiment, the return to the original conditions, his correct answer rate continued to increase.

Pigeons' responses in the presence of two concurrently available (initial‐link) stimuli produced one of two different (terminal‐link) stimuli according to identical but independent variable‐interval schedules. Responses in the presence of each terminal‐link stimulus produced equal frequencies of food reinforcement, but in the presence of one of the stimuli, food depended upon the emission of a response rate either higher or lower than a specified value (differential reinforcement of rates). The measure of preference, the dependent variable, was the distribution of responses in the presence of the concurrently available stimuli of the initial links. Each pigeon, the responding of which was appropriately controlled by the response‐rate requirements in the two terminal‐link stimuli, consistently preferred the stimulus not associated with a response‐rate requirement.

Squirrel monkeys were periodically exposed to brief tail‐shocks in the presence of a rubber tube connected to a pneumatic switch. Biting attack upon this tube was found to be a decreasing function of time since shock delivery and a direct function of shock intensity and duration. These results parallel findings in investigations employing more “naturalistic” social situations, indicating that attack against the inanimate and animate environment is a direct function of the intensity of an aversive stimulus. The results also demonstrate that frequency of biting attack as a datum is sensitive to several experimental manipulations.

The effects of contingent teacher attention on study behavior were investigated. Individual rates of study were recorded for one first‐grade and five third‐grade pupils who had high rates of disruptive or dawdling behavior. A reinforcement period (in which teacher attention followed study behavior and non‐study behaviors were ignored) resulted in sharply increased study rates. A brief reversal of the contingency (attention occurred only after periods of non‐study behavior) again produced low rates of study. Reinstatement of teacher attention as reinforcement for study once again markedly increased study behavior. Follow‐up observations indicated that the higher study rates were maintained after the formal program terminated.

A discrimination was established between two fixed‐ratio schedules of reinforcement. In one, fixed ratio 25, the reinforcer was delivered on the twenty‐fifth response; on the other, fixed ratio 50, the fiftieth response was reinforced. In the first component of a chain, either fixed ratio 25 or fixed ratio 50 was randomly programmed on the center key of a three‐key pigeon box. Reinforcement of a single peck on the side key was contingent upon discriminating which schedule had just been completed on the center key. During test trials, a timeout was introduced after the first response on fixed ratio 25 and after either the first or twenty sixth response on fixed ratio 50. When the timeout followed the first response on fixed ratio 25 and fixed ratio 50, the accuracy of the discrimination was unaffected. When the timeout followed the first response on fixed ratio 25 and the twenty sixth response on fixed ratio 50, the accuracy of the discrimination decreased rapidly to chance as a function of the duration of the timeout. The loss of discrimination was primarily due to errors after fixed ratio 50 was completed. The timeout appears to weaken the control over the choice response by the response‐produced stimuli which preceded the timeout. The results are consistent with the interpretation that the discrimination between fixed ratio 25 and fixed ratio 50 is maintained by chaining of response‐produced stimuli within the ratio cycle.

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