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The contribution of the response‐reinforcer dependency to the control of behavior was investigated. Pigeons were trained to key peck under a variable‐interval schedule of reinforcement. With the total number and temporal distribution of reinforcer deliveries in experimental sessions constant, the effects of varying the percentage of response‐independent reinforcement were examined. At different times, 100%, 66%, 33%, 10%, or 0% of the scheduled reinforcers were delivered dependent upon key pecking and the remainder were delivered independently of responding. Response rates were related to the percentage of response‐dependent reinforcement with lower response rates associated with smaller percentages of response‐dependent reinforcement. The results suggest that the response‐reinforcer relation exerts control over behavior in a manner similar to that exerted by other parameters of reinforcement.

Three rats were exposed to a multiple schedule in which separate presentations of light and tone alternated with periods during which light and tone were absent. In Phase 1, light and tone each signalled identical variable‐interval schedules of food delivery. In Phase 2, light and tone signalled separate but concurrent variable‐interval schedules of food and shock delivery. In both phases, the absence of light and tone was associated with the differential reinforcement of other behavior. Test presentations of light, tone, and a light‐plus‐tone combination indicated that in both phases, light‐plus‐tone controlled higher response rates than either light or tone alone. The combination continued to control enhanced responding even when the test stimuli signalled variable‐interval schedules of food and fixed‐ratio schedules of shock. In these latter sessions, enhanced control by the combination increased shock frequency with no corresponding change in food frequency. Apparently, the level of behavior controlled by the absence of two single stimuli may be more important than the consequences of responding in determining the effects of combined‐stimulus presentations.

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The thrust of this paper is to bring to the attention of operant researchers statistical procedures that are appropriate for correlated data. In addition to specifying these statistical procedures consideration is given to the question of using individual comparison statistics rather than omnibus F tests. Specifically, it is recommended that a more powerful test of the experimental hypotheses can be obtained by performing Bonferroni t statistics rather than analysis of variance F tests.

Different doses of intravenous cocaine reinforced the lever pressing of rhesus monkeys under two‐lever concurrent or concurrent‐chain schedules. Under the concurrent procedure, responding produced drug reinforcers arranged according to independent variable‐interval 1‐min schedules. Under the concurrent‐chain procedure, responding in the variable‐interval link led to one of two mutually exclusive, equal‐valued, fixed‐ratio links; Final Acceptance completion of the ratio produced a drug reinforcer. Under both procedures, responding on one lever produced a constant dose of 0.05 or 0.1 mg/kg/injection, while on the other lever, dose was systematically varied within a range of 0.013 to 0.8 mg/kg/injection. Preference, indicated by relative response frequency on the variable‐dose lever during the variable‐interval link, was always for the larger of the doses. Relative response frequencies on the variable‐dose lever roughly matched relative drug intake (mg/kg of drug obtained on variable lever divided by mg/kg of drug obtained on both levers). For many dose comparisons, responding occurred and reinforcers were obtained almost exclusively on the preferred lever. Overall variable‐interval rates generally were lower than with other reinforcers, and these low rates, under the experimental conditions, may have occasioned the exclusive preferences.

On one key, pigeons' pecks were reinforced according to a variable‐interval schedule in the presence of vertical lines, and were not reinforced in the presence of oblique lines. On a second key, pecks were reinforced according to a variable‐interval schedule in the presence of blue, according to a signalled variable‐interval schedule in the presence of red, and were not reinforced in the presence of white. Subsequently, during extinction, stimulus‐control gradients were obtained by presenting eight different line orientations on the first key concurrent with each of the three colors on the second key. On the first key, line‐orientation gradients tended to be lower, narrower, and less shifted in peak or area when the second‐key stimulus was blue or red, the stimuli respectively correlated with unsignalled and signalled reinforcement, than when it was white, the stimulus correlated with extinction. Thus, the effect on first‐key line‐orientation gradients depended on second‐key stimuli correlated with concurrent reinforcement, whether or not these stimuli were also correlated with concurrent responding. As a function of first‐key line orientation, an inverted gradient was obtained on the second key during blue; during both red and white, rates of pecking on the second key were near zero.

Three experiments were conducted to assess the aversive properties of a visual stimulus in the presence of which one group of birds received response‐contingent shock (discriminated punishment) while a yoked group of birds received non‐contingent shocks (conditioned suppression). In Experiment 1, presentation of the visual stimulus contingent on key pecking reduced the response rate (conditioned punishment effect) for birds under the conditioned suppression procedure but did not reduce the response rate of birds under the discriminative punishment procedure. Non‐contingent shocks also produced greater suppression of responding maintained by positive reinforcement in the presence of a visual stimulus than did response‐contingent shocks. In Experiment 2, a greater shock intensity (2 mA) was used. All the differences between the two groups found in Experiment 1 were also found in Experiment 2. Experiment 3 demonstrated that response‐contingent shock did not result in a conditioned punishment effect even when positive reinforcers were unavailable during the discriminative punishment schedule. The exteroceptive stimulus that was paired with shock in the conditioned suppression procedure acquired the ability to punish behavior. The exteroceptive stimulus in the discriminative punishment schedule did not acquire this ability.

Key pecking of pigeons was maintained under conjunctive schedules of food presentation in which both a fixed‐interval and a fixed‐ratio schedule had to be completed before a peck produced food. For two pigeons, pecks on a single key completed both schedule requirements (fixed‐interval 3‐min, fixed‐ratio 50 for one bird, fixed‐interval 5‐min, fixed‐ratio 50 for the second). For two other pigeons, each requirement was scheduled on a separate key. On the two‐key schedule, a peck after 5 min on the key scheduling the fixed‐interval requirement produced food if at least 10 pecks had occurred on the ratio key (conjunctive fixed‐interval 5‐min, fixed‐ratio 10). When each requirement was scheduled on a separate key, response rates on the fixed‐ratio key were generally higher in the early portion of the interval and declined as the interval progressed; responding on the fixed‐interval key, once initiated, typically remained at a constant rate throughout the interval. Responding under the single‐key schedule was characterized by a high rate early in the interval; this then changed to a lower rate that continued until a peck produced food. For all pigeons, increases in response rates with pentobarbital and d‐amphetamine were inversely related to the control rate of responding. When equivalent rates on each key of the two‐key schedule were compared, both drugs increased rates on the fixed‐ratio key less. Although the effects of both drugs were rate dependent, each drug differentially modified the pattern of responding under the single‐key schedule.

Pigeons made observing responses for stimuli signalling either a fixed‐interval 30‐sec schedule or a fixed‐ratio x schedule, where x was either 20, 30, 100, 140, or 200 and the schedules alternated at random after reinforcement. If observing responses did not occur, food‐producing responses occurred to a stimulus common to both reinforcement schedules. When the fixed‐interval schedule was paired with a low‐value fixed ratio, i.e., 20 or 30, the presentation of the stimulus reliably signalling the fixed‐ratio schedule reinforced observing behavior, but the presentation of the stimulus reliably signalling the fixed‐interval schedule did not. The converse was the case when the fixed‐interval schedule was paired with a large‐valued fixed ratio, i.e., 100, 140, or 200. The results demonstrated that the occasional presentation of the stimulus signalling the shorter interreinforcement interval was necessary for the maintenance of observing behavior. The reinforcement relationship was a function of the schedule context and was reversed by changing the context. Taken together, the results show that the establishment and measurement of conditioned reinforcement is dependent upon the context or environment in which stimuli reliably correlated with differential events occur.

The contingency between conditional and unconditional stimuli in classical conditioning paradigms, and between responses and consequences in instrumental conditioning paradigms, is analyzed. The results are represented in two‐ and three‐dimensional spaces in which points correspond to procedures, or procedures and outcomes. Traditional statistical and psychological measures of association are applied to data in classical conditioning. Root mean square contingency, ø, is proposed as a measure of contingency characterizing classical conditioning effects at asymptote. In instrumental training procedures, traditional measures of association are inappropriate, since one degree of freedom—response probability—is yielded to the subject. Further analysis of instrumental contingencies yields a surprising result. The well established “Matching Law” in free‐operant concurrent schedules subsumes the “Probability Matching” finding of mathematical learning theory, and both are equivalent to zero contingency between responses and consequences.