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Subjects pressed a telegraph key to illuminate a meter dial on which pointer deflections appeared at fixed intervals. Upon detecting a deflection they were required to press another key to reset the pointer to zero. This detecting and resetting operation reinforced the behavior of pressing the light‐flashing key (i.e., the observing responses). The usual pattern of responding on the light‐flashing key was a long pause following the reinforcement and an abrupt transition to a steady response rate toward the end of the interval. When the subjects were required to perform a concurrent subtraction task, the pattern of responding changed in varying degrees, ranging from complete loss of typical fixed‐interval behavior to a slight shortening of the post‐reinforcement pause. These effects were attributed to the disruption of the self‐produced verbal chains (counting or reciting) that ordinarily govern human behavior on this schedule.

Chlorpromazine hydrochloride and d‐amphetamine sulphate were administered to two rats responding on a baseline temporally defined schedule of negative reinforcement which produced both “escape‐like” and “avoidance‐like” behavior. The effects of these drugs appeared similar to those expected on the more customary sort of non‐cued avoidance schedule.

In two experiments, each involving four rats, responses preceded by an inter‐response time between 8 and 10 sec in duration were intermittently reinforced. In Experiment I, final performance was compared under two hunger levels, while the frequency of reinforcement was held constant by a VI 5 schedule. In Experiment II, hunger was held constant and VI 5 was compared with VI 8. Both hunger and frequency of reinforcement increased the over‐all rate of response, but the exact effects of these operations on temporal discrimination were different for different rats. Usually, a peak “response probability” (IRTs/Op ratio) was obtained 8 to 10 sec after the preceding response, indicating adaptation to the reinforcement contingency, but in some cases this peak was about 2 sec earlier. One rat exhibited unusually pronounced bursting which seemed to alternate with adaptive temporally spaced responding. Prolonged pauses, observable in the cumulative records, particularly following reinforcement, were attributed to the fact that inter‐response times greater than 10 sec were not reinforced, so that as the interval of time since the preceding response became discriminably greater than 10 sec, the probability of a response became small.

The progressive ratio schedule requires the subject to emit an increasing number of responses for each successive reinforcement. Eventually, the response requirement becomes so large that the subject fails to respond for a period of 15 min and thereby terminates the session. This point is arbitrarily defined as the “breaking point” of the subject's performance. The measure is quantified in terms of the number of responses in the final completed (i.e., reinforced) ratio run of the session. Previous work has shown that this measure varies as a function of several motivational variables and may thus be useful as an index of reinforcement strength. The present study is an extension of that work. The subjects were four rats. In the first experiment, the effects of the size of the increment by which each ratio run increased were studied. In two additional experiments, the volume of a liquid reinforcer was varied using both large and small ratio increments. The results indicate that the number of responses in the final completed ratio run increases as a function of the size of the ratio increment. However, the number of reinforcements obtained by the animals per session declines sharply. When large ratio increments are used, the number of responses in the final ratio increases as a function of the volume of the reinforcer, but when small increments are used, progressive satiation results in a decline in performance with the larger volumes of liquid.

Certain doses of pentobarbital consistently increased the rate of pecking engendered by a fixed‐ratio schedule of 30 responses in a group of 13 pigeons, and still higher doses produced decrements in rate of responding. For individual subjects, the dose‐effect functions were qualitatively similar, but differed with respect to the doses producing the maximum increase and subsequent decrease in rate. In general, the maximum occurred at lower doses and the decrement was greater at the highest dose in the birds with the highest control rates. It was also possible to distinguish between the effects of pentobarbital and several other drugs on the behavior maintained by FR 30. The results indicate that changes in rate of responding on FR 30 after drug administration are dose‐dependent, drug‐specific effects.

A temporally defined reinforcement schedule within the tau system of classification was studied, with pigeons as subjects and with cycle length as the independent variable. As cycle length decreased, response rates increased, responses‐per‐reinforcement went through a maximum, while the number of reinforcements‐per‐session increased. The first two functions are attributed to changes in the discriminability of the τD and τΔ components of the cycle, while the latter seems to result from changes in the relative durations of reinforcement time and τΔ time.

Mental hospital patients were conditioned to respond at a high rate. Then an attempt was made to eliminate the response by means of a mild punishment consisting of a period of time‐out from reinforcement (response‐produced extinction). When only one response was available for obtaining the reinforcement, the mild punishment was not effective in eliminating that response. When an alternative response was also made available for obtaining the reinforcement, the mild punishment was completely effective. It appears that even very mild punishment may be effective if the over‐all frequency of reinforcement can be maintained by means of an alternative unpunished response.

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