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After discrimination training on a multiple variable‐interval extinction schedule of food reinforcement, pigeons were placed on the uncued or mixed version of the same schedule and allowed to make an optional “observing response” that converted the uncued schedule to the corresponding cued schedule by providing a 20‐sec exposure to the appropriate discriminative stimulus. The schedule consisted of one hundred 40‐sec components, and the probability that any one of them would be a variable‐interval component was systematically varied between 0.00 and 1.00. The results showed that the amount of observing behavior was an inverted “U” function of the probability of the variable‐interval component. Few observing responses occurred at probabilities of 0.00 or 1.00, and maximum responding occurred at a value less than 0.50.

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Pigeons pecked a key and rats pressed a lever for food reinforcement under large values of the differential‐reinforcement‐of‐low‐rate schedule. Each subject was tested under 10 different schedule values ranging from 1 to 45 min and was exposed to each schedule value at least twice. The mean interresponse time and mean interreinforcement time increased with the schedule value according to power functions. Response‐probability functions were computed for schedule values below 20 min and showed an increase in response probability as a function of time since the last response in most cases. Mean responses per reinforcer increased as a function of schedule value for the rats, but decreased as a function of schedule value for the pigeons. The proportion of responses with interresponse times shorter than 1 sec were an increasing function of schedule value for the pigeons, but did not vary as a function of schedule value for the rats.

After an initial period of nondifferential training, six pigeons were trained on a go/no‐go discrimination involving 12 line tilts from vertical clockwise to horizontal. Responses to the first six tilts (positive stimuli) were reinforced on a variable‐interval one‐minute schedule, whereas responses to the other six tilts (negative stimuli) were extinguished. During the first several discrimination sessions, the highest response rate was typically to one of the positive stimuli that was relatively close to the negative stimuli or at an intermediate distance, rather than to one of the positive stimuli most distant from the negative stimuli. This effect decreased with extended training up to 50 or 80 sessions.

Behavioral contrast was obtained in two experiments, which both employed a standard free‐operant successive discrimination (a multiple variable‐interval extinction schedule), without the occurrence of reductions of response rate in the extinction component. In Experiment I, one group of four pigeons was trained on a multiple schedule in which one stimulus was associated with a variable‐interval schedule and the second stimulus with response‐independent reinforcement on a free variable‐interval schedule. Though by the end of this training three pigeons were responding very little to the second stimulus, when this stimulus was associated with extinction all subjects showed a contrast effect. In Experiment II, eight pigeons were trained extensively to respond to a single stimulus on a variable‐interval schedule, before a second stimulus associated with extinction was introduced. This second stimulus was dissimilar to the initial stimulus and five pigeons never responded in its presence. Nevertheless, all pigeons showed a contrast effect and there was no evidence that the effect was smaller in errorless subjects or smaller than in a subsequent discrimination where all subjects made many errors. Both experiments indicated that response reduction in one component of a multiple schedule is not a necessary condition for the occurrence of contrast.

In Experiment I, two groups of four pigeons each were exposed to multiple schedules in which one component was always a variable‐interval schedule with a mean interreinforcement interval of 30 or 180 seconds. The other component was either an equal variable‐interval schedule or extinction. Response rates in the unchanged component always increased when reinforcement was no longer scheduled in the changed component, and decreased in seven of eight cases when the variable‐interval schedule was re‐introduced. The per cent rate change in the unchanged component was inversely related to the frequency of reinforcement and to the ongoing response rate in the unchanged component. Rate changes in the unchanged component were not consistently correlated with changes in any single feature of the relative‐frequency interresponse‐time distributions. In Experiment II, the same pigeons were exposed to variable‐interval schedules and multiple variable‐interval variable‐interval schedules with equal mean interreinforcement intervals. Response rates were similar under both conditions.

Four pigeons were initially trained under a multiple variable‐interval 1‐min variable‐interval 1‐min schedule of food reinforcement. For two of the pigeons, a signal was then presented whenever the reinforcer was available in one component; this resulted in positive contrast. For the other two pigeons, the reinforcer was presented independently of responding on a variable‐time schedule in one component; this resulted in negative induction. After 30 to 50 sessions, however, a similar degree of differential responding occurred under both multiple schedules, i.e., high rates in the variable‐interval component and low rates in the other component. Reinforcement frequency remained about the same in each of the schedule components. The stable performances then served as baselines for studying drug effects. In the high‐rate component of both multiple schedules, small doses of d‐amphetamine increased responding, whereas larger doses decreased responding. In the low‐rate component of both multiple schedules, there was no rate‐increasing effect at any dose of d‐amphetamine; such an effect was found, however, with phenobarbital at a dose that decreased responding in the high‐rate component. The drug effects thus depended on the interaction of pharmacologic variables (specific drug and dose) with behavioral variables (schedule components).

Applied behavior analysis, as a special case of behavioral technology, is discussed from the standpoint of behavioral ecology. The ecological orientation and its emphasis upon system‐like interdependencies among environment, organism, and behavior are presented. The widespread possibilities for unintended effects of simple interventions provide the context for evaluating effective behavioral technology and calling for cooperation between the technologist and ecologist. Such cooperation, in the form of mutual and cooperative research efforts, should come naturally for the technologist and ecologist, because they share some fundamental values and assumptions, and each has much to offer the other. Several areas of such cooperative effort are spelled out.