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In two experiments, squirrel monkeys were exposed to centrifugally generated, artificial gravity and trained to respond for food reinforcement at selected gravity (g) levels. Experiment I involved a single g value; in Exp. II, subjects were trained to discriminate among two or three g values. After training, generalization tests were administered over a 1.1‐g to 2.1‐g range. The major findings were as follows: (a) single‐stimulus training yielded a linear relationship between percentage of responding and magnitude of gravity. (b) Two‐valued discrimination training produced gradient peaks which were shifted from SD in a direction away from SΔ. This effect was cancelled when SD was located equidistant between two SΔ stimuli, (c) Gradient form was independent of the SD‐SΔ difference, but related to continuum location and/or intensity of discriminative stimuli.

In pigeons responding under a 180‐sec fixed‐interval schedule of reinforcement, the frequency distribution of the duration of the final interresponse time before the reinforcer was compared with the distribution of the preceding two interresponse times. The results confirmed qualitatively and quantitatively the expected preferential reinforcement of longer interreinforcement times under fixed‐interval reinforcement. Requirements at reinforcement were then changed to eliminate the preferential reinforcement of longer interresponse times. Local patterns and mean rate of responding could change, without the characteristic fixed‐interval pattern of increasing responding through the interval (scalloping) being much affected. It is concluded that this characteristic pattern of fixed‐interval responding does not depend crucially on effects of the reinforcer at the moment of reinforcement, but rather to effects extending over much longer periods of time than just the last interresponse time.

Three rats were trained on a schedule in which every sixth response produced a timeout of 5 sec minimum duration, and food was delivered at the onset of timeout. Successive interresponse times were measured under these conditions, and also when behavior was maintained by second‐order fixed‐ratio and fixed‐interval schedules. Under the second‐order schedules, each six‐response fixed‐ratio component was followed by a timeout, and occasionally food was delivered at the onset of a timeout. In the fixed‐ratio schedule, the successive interresponse times showed a decrease followed by an increase before food delivery, but this systematic variation in interresponse times was not found when the performance was under second‐order reinforcement. Under both second‐order schedules the latencies of successive components, and the successive interresponse times within each component, showed a decrease as food delivery was approached.

The speech disfluencies of five normal‐speaking college students were modified in a series of 10 to 17 sessions by means of response cost. During Point‐loss, each disfluency (repetition or interjection of a sound, syllable, word, etc.) resulted in the loss of a penny, as indicated on a screen in front of the subject. Disfluencies were suppressed and kept at very low levels for four of the subjects during the punishment procedures, and there was general resistance to extinction. Even though points were subtracted only during speech, there was a tendency for disfluencies to decrease, though not as markedly, during reading probes as well.

Two experiments were conducted by the mothers of the children in a Head Start classroom. Both examined the effects of a switching task on the frequency with which children moved from one activity area of the classroom to another. The results indicated that the rate at which the children changed activities could be adjusted by varying the difficulty or magnitude of the switching task and that the task itself could be used to introduce academic subjects which would be poorly attended if initially presented in an activity area.

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