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In a chamber with a single response key, pigeon's key pecks were reinforced with food according to a variable‐interval schedule. In addition, extra reinforcements occurred concurrently according to an independent schedule. In one condition, availability of the extra reinforcements was signalled by a change in key color from white to red. The extra reinforcements occurred after a peck on the red key. In a second condition, the extra reinforcements were unsignalled and occurred only after a 2‐sec pause in pecking for one group of subjects and were unsignalled and occurred freely as scheduled for another group of subjects. In the first two conditions, duration of reinforcement was varied. A third condition duplicated the second but varied rate rather than duration of reinforcement. The rate of pecking varied inversely with the amount of extra reinforcement per unit time according to the same function, regardless of the condition regulating occurrence of the extra reinforcements, and regardless of whether or not a 2‐sec pause was required for their occurrence. The shape of this function was predicted by Herrnstein's (1970) matching law.

Young adults performed a lever‐pressing task for money on two schedules of reinforcement: concurrent fixed‐interval 1 min—differential‐reinforcement‐of‐low‐rate 20‐sec, and concurrent fixed‐interval 1‐min—fixed ratio 100 responses. All subjects were trained on both schedules. Fixed‐interval performance concurrent with the differential reinforcement procedure was characterized by high constant rates with no post‐reinforcement pauses. Fixed‐interval performance concurrent with fixed ratio was characterized by low rates and lengthy post‐reinforcement pauses. These results differ from those obtained in prior studies on the effects of conditioning history upon subsequent fixed‐interval performance. The prior work, using non‐concurrent procedures, had shown that fixed‐interval performance following differential reinforcement of low rates was characterized by post‐reinforcement pauses and low rates, while fixed‐interval performance following fixed ratio exhibited high constant rates and no post‐reinforcement pause. The present results suggest that alternative concurrent contingencies are another major determinant of human fixed‐interval performance.

Two experiments studied responding in the rat when the first bar press after a variable period of time produced a cue light that remained on for either 10, 30, or 100 sec and terminated with the delivery of food. In Experiment I, response rate decreased and time to the first response after reinforcement increased as the delay of reinforcement increased. Similar results were obtained whether the delay consisted of retracting the lever during the delay, a fixed delay with no scheduled consequence for responding, or every response during the delay restarted the delay interval. In Experiment II, fixed‐delay and fixed‐interval schedules of the same duration during the delay period had no differential effect on either response rate or time to the first response after reinforcement, but differentially controlled responding during the delay periods.

Chicks were hatched and raised in white or monochromatic sodium (589 nm) light. They were trained on a 590 (+) vs. 580 (‐) nm successive discrimination. The combined results of two experiments indicated that rearing illumination did not affect discrimination acquisition. All subjects given generalization tests after discrimination training exhibited peak shifts that were equivalent for the two rearing conditions. The peak shifts exhibited by the monochromatically reared subjects represent maximum responding to stimuli they had not previously seen. This result further confirms the notion that behavioral control by the spectral dimension in birds is organized independently of differential early experience on that dimension.

The effects of two different motivational conditions upon standardized test performance were explored for two student populations. The first study involving 12 trainable retardates showed a significant increase in score on the Metropolitan Readiness Test given under reinforcement conditions when these results were compared with scores taken under standard testing conditions. In a second study, these same results were obtained with a group of 30 normal fourth‐graders. An additional study was conducted to determine the effect of different experiences with token reinforcement procedures on test performance. It was found that a group of children with six weeks' exposure to reinforcement for daily academic performance scored higher under both conditions of test administration (standard and reinforcement) than a control group. However, in a single exposure to token reinforcement for correct performance on the Metropolitan Test, both the experimental group and its match control showed a parallel increase in test performance. These findings offer a procedure that yields a more representative assessment of a student's academic achievement than does testing under standard conditions.

Two experiments investigated free‐operant avoidance responding with pigeons using a treadle‐pressing response. In Experiment I, pigeons were initially trained on a free‐operant avoidance schedule with a response‐shock interval of 32 sec and a shock‐shock interval of 10 sec, and were subsequently exposed to 10 values of the response‐shock parameter ranging from 2.5 to 150 sec. The functions relating response rate to response‐shock interval were similar to the ones reported by Sidman in his 1953 studies employing rats, and were independent of the order of presentation of the response‐shock values. Shock rates decreased as response‐shock duration increased. In Experiment II, a free‐operant avoidance schedule with a response‐shock interval of 20 sec and a shock‐shock interval of 5 sec was used, and shock intensities were varied over five values ranging from 2 to 32 mA. Response rates increased markedly as shock intensity increased from 2 to 8 mA, but rates changed little with further increases in shock intensity. Shock rates decreased as intensity increased from 2 to 8 mA, and showed little change as intensity increased from 8 to 32 mA.

Teacher attention was systematically manipulated to modify digit‐reversal behavior in an elementary school child. Almost invariably, the child reversed the order of digits (e.g., writing 21 as the sum of 5 + 7) when adding numbers yielding a two‐digit sum. The child, along with classmates, was given 20 addition problems a day for the duration of the study, and the number of reversals was recorded. During an initial baseline period, the teacher responded to digit reversals by marking them as incorrect and then giving the child “extra help” until all sums were correctly ordered. The child's present and previous teacher had both responded to reversals in this manner for approximately one year before the present study began. An experimental period followed during which the rate of reversals decreased sharply. During this period, all sums were marked as correct (whether reversed or not); “extra help” with reversals was discontinued; and correct, i.e., non‐reversed, response forms were responded to with a smile, a pat on the back, and a brief comment. A reversal period followed, during which the teacher responded to reversals as she had in the first baseline period. An increase in the rate of reversals to baseline level occurred within three days. A final period, replicating the first experimental period followed, and was characterized by a sharp decrease in the rate of reversals.

A multiple schedule was arranged in which each component consisted of two, concurrent variable‐interval schedules of reinforcement. A changeover‐key procedure was used, and the components of the multiple schedule were distinguished (initially) by the color of the changeover key. During one component of the multiple schedule, the availability of a reinforcer arranged by one of the variable‐interval schedules was marked by an exteroceptive stimulus, provided that that variable‐interval schedule was not at the time assigned to the main key. During the other component of the multiple schedule, no reinforcer‐correlated stimuli were ever presented. During the latter component of the multiple schedule, the distribution of responses and time for the concurrent variable‐interval schedules suggested control by the distribution of reinforcements. During the former component, most main‐key responses were emitted on the key in the presence of which reinforcer‐correlated stimuli were presented. Changeover rate in the presence of that key color was depressed. The discriminative control over the changeover was easily established and was reversible.

The key pecking of two pigeons was reinforced with food on a progressive‐ratio schedule, which required an increasing number of responses for each successive reinforcement: 8, 16, 24, 32, etc. When the subject failed to complete the next ratio in the sequence within 60 min, the session terminated. The number of responses in the final completed ratio was defined as the “breaking point”. After the breaking point had stabilized (60 sessions), it served as a baseline to assess the effects of varying doses (5 to 80 mg/kg) of chlordiazepoxide and phenobarbital, administered intramuscularly 30 min before the sessions. Both drugs increased the breaking point. The dose‐effect curves were inverted U‐shaped, with maximum enhancement of performance occurring at 20 mg/kg for chlordiazepoxide and at 40 mg/kg for phenobarbital. A comparable enhancement was not obtained during a non‐drug “probe” session, which was conducted after the subjects' body weights had been temporarily reduced from 80% to 70% of their free‐feeding weights. The drug‐induced enhancement of breaking point was related to the initial values of the performance and may represent a reduction in the aversiveness of the schedule.