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Experiment I sought to determine if the stimulus correlated with extinction in a successive discrimination was an aversive stimulus. An escape response provided an index of aversive control. Two groups of pigeons were exposed to a multiple variable‐interval 30‐sec extinction schedule. For the experimental group, a single peck on a second key produced a timeout during which all lights in the chamber were dark. For the control group, pecks on the second key had no contingency. The rate of responding on the timeout key during extinction for the experimental group was higher than that of the control group during all sessions of discrimination training except the first. In Exp. II, green was correlated with variable interval 30‐sec and red was correlated with variable‐interval 5‐min. Timeouts were obtained from variable‐interval 5‐min. There were more timeouts from extinction in Exp. I than from variable‐interval 5‐min in Exp. II. Experiment III showed that not presenting the positive stimulus reduced the number of timeouts from the negative stimulus for the two birds from Exp. I that had the highest rate of timeouts from extinction, but had little effect on the two birds that had the lowest rate of timeouts. These results suggest that in a multiple schedule, the stimulus correlated with extinction, or the lower response rate, functions as a conditioned aversive stimulus. Explanations of the timeout response in terms of extinction produced variability, displaced aggression, and stimulus change, were considered but found inadequate.

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Techniques of behavior modification were employed with two second‐grade Negro girls in a demonstration school for culturally deprived children to increase the girls' appropriate classroom behaviors. A classification system that provided for continuous categorization of behavior was used to code the children's behavior in two classroom situations. Data were also taken on the type, duration, and frequency of the teachers' verbal interactions. The study included four conditions: Baseline, Modification I, Postmodification, and Modification II. The treatment variable was positive social reinforcement—attention and approval contingent upon desirable classroom behaviors—which was presented, withheld, or withdrawn (timeout from social reinforcement). Withholding of social reinforcement was contingent upon inappropriate attention‐getting behaviors. Timeout from social reinforcement was contingent upon behaviors classified as aggressive and resistive. After 25 days of Modification I, desirable behavior increased markedly for each girl. The teachers were then asked to return to their Baseline level of performance. The resultant behaviors demonstrated that for one girl, behavior was still primarily under the control of the treatment contingencies. For the second child, many desirable behaviors that had increased in frequency during Modification I remained high, but inappropriate behaviors increased. When treatment was reinstated, the amount of time spent in desirable behaviors increased and remained high for both girls. Three checks during the three months following data collection showed that these behaviors continued to remain high.

In each of two experiments, the rate of key pecking maintained by a variable‐interval food reinforcement schedule was measured, first when that schedule was studied in isolation, and then when it was correlated with the second component of a two‐component chained schedule. In the first experiment, the first component of the chained schedule was correlated with a fixed‐interval schedule; in the second experiment it was correlated with a variable‐interval schedule. In both experiments, behavioral contrast was demonstrated in the second component of the chained schedule. Compared to the rate of responding on the food‐reinforcement schedule when it had operated in isolation, the rate of responding on the food‐reinforcement schedule when it was correlated with the second component was higher, while the rate on the schedule of the first component was lower. The results are discussed with reference to the determinants of contrast.

The key pecks of four pigeons were reinforced on a variable‐interval 5‐min schedule which operated in each of the four components of a multiple schedule, indicated by red, green, yellow, and blue stimuli and presented in such an order that the red stimulus always preceded the yellow and the green stimulus always preceded the blue. After establishing baseline rates, the reinforcement schedule associated with the blue and yellow components was altered so that one was now an extinction schedule and the other was a variable‐interval 1‐min schedule. In a second experimental stage, the blue stimulus was interchanged with the yellow so that the red stimulus preceded the blue and the green stimulus preceded the yellow. In both experimental stages the response rate in the variable‐interval 5‐min component that preceded the extinction component was higher than the response rate in the variable‐interval 5‐min component that preceded the variable‐interval 1‐min component. The results were discussed in relation to the importance of stimulus ordering in experiments concerned with investigating behavioral contrast.

Avoidance conditioning procedures were used to train cats to discriminate intensity differences between successive clicks. The discriminative behavior was applied in a modified method of adjustment to determine a difference limen (DL) for click intensity. The obtained DLs were consistent within and between subjects, and averaged 4.4 db. This value is greater than previously reported intensity DLs for pure tones in cats.

Past studies have shown that stuttering is eliminated when speech is synchronized with a metronomic beat, but the speech sounds artificial. The present study investigated the effect of increasing the duration of these individual stimulus beats with the stimulus‐off period constant at 1 sec. When subjects were instructed to speak during the stimulus‐on period, stuttering was an inverse function of stimulus duration, indicating that the known metronome effect on stuttering is one point on a continuum of effective rhythm procedures. The “naturalness” of speech increased as the stimulus duration increased up to durations of about 2 sec, and then decreased. At optimal values, stuttering was greatly reduced and naturalness and rapidity of speech were retained. These optimal values effectively controlled stuttering in a field test that used two types of specially designed portable instruments, one of which produced a tactual stimulus and the other an auditory stimulus.