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The pigeon and the rat partition total response output between both schedules of a concurrent variable‐interval pair. The quantitative nature of a partition seems critically dependent on the relative rates with which the two schedules provide reinforcements for responding, in addition to the changeover delay. The manner in which the changeover delay controls the partition was studied by varying the duration of the changeover delay from 0 to 20 sec with each of two pairs of concurrent variable‐interval schedules, viz., Conc VI 1.5‐min VI 1.5‐min and Conc VI 1‐min VI 3‐min. Rats served as the subjects and brain stimulation was employed as the reinforcer. When the schedules were Conc VI 1.5‐min VI 1.5‐min, relative response rate approximated 0.50 at all values of the changeover delay. When the schedules were Conc VI 1‐min VI 3‐min, relative response rate, computed with respect to the VI 1‐min schedule, increased when the duration of the changeover delay increased. Changeover rate decreased when the duration of the changeover delay increased. The decrease was the same for both VI schedules of the Conc VI 1.5‐min VI 1.5‐min pair but was more rapid for the VI 3‐min schedule of the Conc VI 1‐min VI 3‐min pair.

Pigeons were trained to peck either of two response keys for food reinforcement on equated aperiodic schedules. The distribution of responding at the two keys was studied as reinforcement was delayed for various durations. The relative frequency of responding at each key was shown to match the relative immediacy of reinforcement, immediacy defined as the reciprocal of the delay of reinforcement.

Male Japanese quail were classically conditioned to display courting behavior at the sound of a buzzer, a previously neutral stimulus. The buzzer (conditioned stimulus) was paired with the presentation of a female quail (unconditioned stimulus) for a number of trials. The courting display, invariably elicited from the male by the presentation of the female, began to appear in part to the conditioned stimulus as early as the fifth pairing. All components of the display were elicited from all birds by the conditioned stimulus alone within 32 pairings of the conditioned and unconditioned stimuli.

Three rhesus monkeys, physically dependent on morphine, were trained to press a lever for food on a fixed ratio of 10 responses. A tone, initially a neutral stimulus, was aperiodically presented every third or fourth session, 5 min before and after the intravenous injection of nalorphine, a morphine antagonist which produces an immediate withdrawal syndrome in morphine‐dependent monkeys. After several sessions, conditioned suppression of food‐lever response rate was observed. Conditioned bradycardia, emesis, and excessive salivation also occurred. In 40 to 45 sessions the conditioned suppression of food‐lever response rate and the conditioned autonomic changes were extinguished by presenting pairings of a tone and saline injection. The monkeys were then reconditioned by presenting the tone aperiodically, every third or fourth session, 5 min before and after the intravenous injection of nalorphine. Results were similar to the initial conditioning sessions. Two rhesus monkeys not dependent on morphine were stabilized on a food schedule similar to that used for the first three monkeys. These monkeys showed no change in food‐lever response rate during or after nalorphine injections.

Operant reinforcement of aggression was studied in food‐deprived pigeons by delivering food for attacks against a target pigeon. The food was delivered according to a fixed‐interval schedule and attack behavior was recorded automatically. Attack could be conditioned and extinguished, and the proportion of time spent in attack was a direct function of the frequency of reinforcement of the attack. The fixed‐interval schedule produced an increasing rate of attack during the interval between food reinforcements. This positive curvature was an inverse function of the duration of the interval. The findings revealed that the duration and temporal patterning of the complex social behavior of attack can be influenced in a substantial and predictable manner by the schedule and frequency of operant reinforcement.

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Rats were given daily 1‐min variable‐interval sessions for several types of food delivered in various amounts per reinforcement and the concurrent, schedule‐induced polydipsia was measured. Dry, solid food was neither a necessary nor sufficient condition for the development of polydipsia. Small portions of liquid Standard Monkey Diet produced polydipsia, but 45‐mg dextrose or sucrose pellets did not. Within the range studied, smaller portions of both solid and liquid foods produced more drinking than larger portions per reinforcement. Two‐min variable‐interval sessions produced a greater polydipsic response than 1‐min variable‐interval, even though the number of 45‐mg Noyes pellets allowed per session was held constant. Polydipsia was greatly attenuated on these schedules when the number of pellets remained constant, but were delivered two at a time. Within the ranges studied, the concurrent polydipsic response was increased by decreasing the rate of food acquisition, either by using smaller portions of food per reinforcement or by increasing the interreinforcement time.