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Heterosexual responsiveness, measured by penile responses and reports of behavior, was strengthened in three homosexuals through a fading procedure. Using two slide projectors, colored slides of nude females were superimposed on colored slides of nude males. As the sexual response was emitted, the nude male was faded out and the nude female faded in. Heterosexual arousal decreased when the fading procedure was reversed or stopped and increased once again when fading was resumed. Homosexual arousal remained high during this experiment but had decreased in two subjects at follow‐up. The results suggest that fading was responsible for altering stimulus control of sexual arousal and that aversive techniques may not be necessary in the treatment of sexual deviation.

In Experiment 1, two groups of pigeons were exposed to multiple variable‐interval 1‐min variable‐interval 1‐min schedules of reinforcement. The required response was a key peck for one group, and a foot press of a bar for the other. When the procedure was shifted to multiple variable‐interval 1‐min extinction, positive contrast occurred with pigeons that key pecked, whereas negative induction occurred with those that bar pressed. Moreover, the absence of contrast could not be ascribed to the lack of inhibition, since negative generalization gradients after bar press training were U‐shaped in Experiment 2. The results are discussed in terms of possible relationships between positive contrast and the phenomenon of autoshaping.

Rhesus monkeys were trained on a fixed‐interval 9‐min limited‐hold 3‐min schedule of intravenous cocaine reinforcement. A 15‐min timeout followed each reinforcement or limited‐hold expiration. An identical schedule of food reinforcement was interspersed in the session to assess rate‐modifying effects of the drug infusions not specific to drug reinforcement. In one experiment, response rate for cocaine reinforcement was shown to be a positive function of reinforcement magnitude for a dose range from 0 to 800 ug/kg/inj. At these doses, there was little effect on food reinforced responding except at the highest dose, where responding decreased. Results of the second experiment indicated that increasing the duration of the cocaine infusion produced a change in response rate similar to decreasing unit dose. The response rate change for a given increase in infusion duration was less at a unit dose of 400 ug/kg than at 200 ug/kg.

Fixed‐interval schedules of intravenous cocaine presentation were examined as a function of injection dose (0.32 to 0.64 mg/kg) and interval duration (200 to 400 sec) in two rats. Cocaine was found to exert a dose‐related temporal control over the initiation of responding that was unaffected by the fixed‐interval contingency. Fixed‐interval pause duration was linearly related to injection dose and was the same duration as the interresponse time found on continuous reinforcement schedules of cocaine presentation. The fixed‐interval pause remained constant with changes in interval duration. Characteristic fixed‐interval patterns of responding were observed. However, overall response rates were inversely related to injection dose and directly related to interval duration. Running response rates varied unsystematically with both variables. These findings are at variance with results typically found in studies of fixed‐interval food and electric shock presentation.

Eight pigeons matched to sample under second‐order schedules of food reinforcement. Under fixed‐interval unit schedules, the first correct match to occur after a given period of time was followed by the presentation of a brief stimulus. The termination of the last fixed‐interval unit schedule was followed by food according to second‐order fixed‐ratio and variable‐ratio schedules. In Experiment 1, as the number of fixed‐interval unit schedules increased, long pauses occurred under the second‐order fixed‐ratio schedules, but not under the variable‐ratio schedules. The similarity of performance measures such as local rate and accuracy indicated that the differences engendered by these two types of schedule are in the duration of the periods of not‐responding. In Experiment 2, the addition of a brief stimulus at the end of each unit schedule in chained schedules that had different discriminative stimuli present for the duration of each unit did not substantially affect the performance, and long pauses continued to occur. However, few long pauses occurred under schedules with brief stimulus presentations alone. The most inaccurate performances were engendered by chained schedules without brief stimuli.

Twelve pigeons were trained on matching‐to‐sample using either a 0‐, 5‐, 15‐, 25‐, or 60‐sec intertrial interval. Eight of these 12 pigeons were given one of the following intertrial interval changes: 0 to 60, 0 to 5, 5 to 0, 60 to 0, 15 to 25, 5 to 15, 60 to 5, 5 to 1, 1 to 5, 1 to 25, and 25 to 1 sec. Most intertrial interval changes were repeated at least once. The 0‐sec intertrial interval subjects failed to match beyond chance levels, while other intertrial interval values resulted in matching acquisition. Changes from 0 sec to other intertrial interval values increased and changes to 0 sec decreased matching performance. Changes to intertrial interval values other than 0 sec resulted in little change in matching accuracy once stable performance had been attained.

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