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Children 4 to 7 yr in age were reinforced with trinkets and pennies on chained and tandem schedules. The schedules used were chain DRL FR, chain DRO FR, chain FI FR, tand FI FR, and tand DRO FR. Chain DRL FR and chain DRO FR schedules almost always produced strong schedule and stimulus control, but chain FI FR schedules rarely did if additional techniques were not used. Strong control was produced with chain FI FR schedules, however, if: (a) the FR component was increased in size; (b) schedule and stimulus control was first established with chain DRL FR or chain DRO FR schedules before shifting to the chain FI FR; or (c) an external clock was attached to the FI. Tand FI FR schedules never produced regular or repeatable patterns of responding when additional procedures were not used. Rate patterns resembling those of chain FI FR schedules were produced by tand FI FR schedules, however, if: (a) an external clock was attached to the FI component or (b) control was established by means of tand DRO FR schedules before the tand FI FR was used. Stimulus control was found to be exercised by specific visual stimuli, change of stimuli, and schedule order. Control exercised by schedule order was probably mediated by the child's own behavior which had assumed discriminative stimulus properties.

Three white rats were trained to press a bar while being shocked. This produced a white noise. After 30 sec they were allowed to terminate both the shock and the noise by nosing a pigeon key. Comparison of the rates of pressing before and after the onset of the noise indicated that the noise itself was the immediate reinforcing agent for pressing. Furthermore, control tests showed that pressing was maintained only if it produced the noise: either omission of the noise or elimination of the dependency of the noise on the occurrence of the response led to a gradual abolition of pressing. When automatic termination of the shock was substituted for the key nosing requirement, however, only the key nosing extinguished. This indicated that the effectiveness of the noise as a reinforcer did not depend on its status as a discriminative stimulus for some other form of operant behavior.

Three variables were studied for their single and joint effects on aversive thresholds obtained by a titration schedule with electric shock as the aversive stimulus. One variable was the interval between the periodic increments in shock amplitude. Another was the size of this increment. The third was the size of the decrement produced when the subject responded. Both monkeys and humans tolerated more shock at the shorter increment‐to‐increment intervals than at the longer ones, confirming rat data previously obtained. Reducing the decremental step size also led to an increase in the amount of shock tolerated by monkeys. In addition, simply reducing both incremental and decremental step size without changing the interval between increments led monkeys to tolerate more shock. The attempt to explain these data was based on the changes that such manipulations might produce in the amount of avoidance behavior elicited.

A graphical method has been developed for the concurrent recording of heart beats and lever responses during behavioral experiments. The EKG signal fed into any DC amplifier goes to a fixed level trigger circuit and relay driver with its own power supply. The signal from this drives any standard cumulative recorder. Lever response rates are recorded concurrently on an additional cumulative recorder using the same paper speed.

When a pigeon's pecking on a single key was reinforced by a variable‐interval (VI) schedule of reinforcement, the rate of pecking was insensitive to changes in the duration of reinforcement from 3 to 6 sec. When, however, the pigeon's pecking on each of two keys was concurrently reinforced by two independent VI schedules, one for each key, the rate of pecking was directly proportional to the duration of reinforcement.

When a pigeon's pecks on two keys were reinforced concurrently by two independent variable‐interval (VI) schedules, one for each key, the response rate on either key was given by the equation: R1 = Kr1/(r1 + r2)5/6, where R is response rate, r is reinforcement rate, and the subscripts 1 and 2 indicate keys 1 and 2. When the constant, K, was determined for a given pigeon in one schedule sequence, the equation predicted that pigeon's response rates in a second schedule sequence. The equation derived from two characteristics of the performance: the total response rate on the two keys was proportional to the one‐sixth power of the total reinforcement rate provided by the two VI schedules; and, the pigeon matched the relative response rate on a key to the relative reinforcement rate for that key. The equation states that response rate on one key depends in part on reinforcement rate for the other key, but implies that it does not depend on response rate on the other key. This independence of response rates on the two keys was demonstrated by presenting a stimulus to the pigeon whenever one key's schedule programmed reinforcement. This maintained the reinforcement rate for that key, but reduced the response rate almost to zero. The response rate on the other key, nevertheless, continued to vary with reinforcement rates according to the equation.

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