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Animals were trained to displace any one of five response keys in order to put themselves in a stimulus condition in which reinforcement could be obtained by depressing a response lever. Decreased deprivation and magnitude of reinforcement were found to increase the variability of the distribution of key responses. The relevance of these findings to other experiments in which deprivation, reinforcement magnitude, and intermittent reinforcement were studied is discussed.

This study was undertaken to determine whether any EEG changes occurred during a multiple schedule of reinforcement consisting of repeated periods of avoidance behavior, a time‐out (TO) period, and a period of differential reinforcement of low rates (DRL). The two monkeys were permanently implanted with bipolar electrodes in various subcortical areas. The EEG was recorded from these electrodes for several weeks before any behavioral training was undertaken. Training was then begun in the multiple schedule, and EEG recordings were taken frequently throughout the training period. When a stable performance level was achieved, drugs (dl‐amphetamine and sodium pentobarbital) were introduced which disrupted the DRL performance but had little or no effect on avoidance behavior. The EEG recordings continued throughout these drug studies.The data indicate that the marked behavioral differences noted in each component of the schedule were not reflected in the EEG. However, the EEG did correlate with the general level of alertness of the animals during the various components. The drugs which differentially affected the behavior in the components of the schedule did not differentially affect the EEG, but they did change the brain‐wave activity equally in all components. Finally, EEG changes correlated with the complex motor response of lever pressing were not observed.

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Two pigeons were exposed to several fixed‐interval schedules of food reinforcement. In some cases, exteroceptive stimuli associated with the passage of time were present. Such visual “clock” stimuli were found to gain almost complete control over the behavior, although at the longest fixed interval studied, the superposition of a new temporal discrimination upon the visual discrimination was observed. Where clock stimuli were made contingent upon the birds' behavior, a new form of responding was generated. This behavior was discussed in terms of positive and negative response‐tendencies resulting from several stimulus factors: Some of these functioned as SΔ's and secondary negative reinforcers; some functioned as SD's and secondary positive reinforcers; and some were ambiguous with respect to reinforcement conditions. A “pure temporal” discrimination was superimposed upon these factors, but its exact nature was indeterminate from the present data.

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In a chained FI FR schedule, manipulating the length of the FI component produced changes confined almost entirely to the FI performance; increasing the interval length increased the total number of responses emitted per reinforcement. The configuration of the fixed‐interval scallop was clearly modified as the interval length was increased, with the larger intervals becoming flatter (i.e., a larger proportion of the total responses earlier in an interval). Measurement of the postreinforcement pause is suggested as a possible indicator of fixed‐interval scalloping.

The experiment was designed to find the shape of food satiation curves of the pigeon as a function of hours of deprivation or percentage of free‐feeding weight, and to study the fluctuation in free‐feeding weight as a function of deprivation and satiation. At a systematically and progressively increased number of hours' deprivation, eight birds were allowed to satiate on grain presented contingent upon the emission of a pecking response. In the second part of the experiment, in which two birds were used, a similar procedure was followed except that the independent variable was percentage of free‐feeding weight. These were the conclusions. . Approximately 64% of the satiation curves were classified as straight with an abrupt stop. The next highest percentage of curves was 18% for curves classified as straight with a curvilinear stop. No “classic” satiation curves, curvilinear with curvilinear stop, were found. . The pigeons responded at fairly constant rate during the early part of each satiation session, or they did not respond at all. The critical weight, above which they did not respond, was 85% of free feeding.

Three groups of four rats were trained on an auditory‐intensity discrimination for 21 days. The SD‐SΔ intensity difference for Group I was 10 db; for Group II, 20 db; and for Group III, 30 db. Following the initial discrimination training, the animals were tested for generalization of the bar‐press response to seven novel SΔ's which were presented intermingled with the original SD and SΔ values. Conclusions: (1.) The amount of simple discrimination training required to obtain fairly stable differences in SD and SΔ responding is an inverse function of the magnitude of the stimulus difference between SD and SΔ. (2.) Generalization gradients obtained immediately following simple discrimination training exhibit a maximum displaced from SD in a direction also away from SΔ. (3.) Gradients obtained following continued exposure to the multivalued SΔ situation show a fairly stable maximum at the SD value. (4.) Although the gradients tend to fall off systematically on either side of the continuum as distance from SD is increased, they decrease most rapidly on the SΔ limb of the gradient.

A more direct method than the usual ones for obtaining inhibitory gradients requires that the dimension of the nonreinforced stimulus selected for testing be orthogonal to the dimensions of the reinforced stimulus. In that case, the test points along the inhibitory gradient are equally distant from the reinforced stimulus. An attempt was made to realize this condition by obtaining inhibitory gradients along the frequency dimension of a pure tone after discrimination training in which the nonreinforced stimulus was a pure tone (or tones), and the reinforced stimulus was either white noise or the absence of a tone. The results showed that some degree of specific inhibitory control was exerted by the frequency of the tone, although the gradients were broad and shallow in slope.A further experiment was conducted to see whether the modification of an excitatory gradient resulting from training to discriminate neighboring tones could arise from a simple interaction of inhibitory and excitatory gradients. The results indicated that it could not, since discrimination training produced a concentration of responding in the vicinity of the reinforced stimulus which cannot be derived from any plausible gradient of inhibition.