Response-dependent and response-independent timeout from an avoidance schedule

While rats were responding in a single-lever apparatus to avoid electric shock, a signal was presented and followed by a 5-min timeout period when all shocks were omitted. For the response-dependent member of each yoked pair, the first response 60 sec after onset of the pre-timeout signal terminated the signal and initiated timeout. The other, yoked animal was exposed to the same sequence except that signal termination and timeout onset were response independent. Under the response-dependent condition, response rates in the presence of the signal increased relative to baseline rates. Rate increases also occurred when timeout was response independent, but were of lesser magnitude and reliability. Subsequent reversal of the yoking arrangement produced stable and equivalent rate increases under both conditions. Other findings were that increased rates in the presence of the signal diminished when timeout was omitted but were maintained for a time on an avoidance-extinction baseline. In general, the results supported the conclusion of previous experiments that timeout from avoidance can serve as a positive reinforcer. The finding that response-independent presentation of timeout produced rate increases, particularly after a history with response-dependent timeout, was interpreted in terms of adventitious reinforcement of previously established behavior.     

Effects of concurrent response-independent reinforcement on fixed-interval schedule performance

In three experiments, behavior maintained by fixed-interval schedules changed when response-independent reinforcement was delivered concurrently according to fixed- or variable-time schedules. In Experiment I, a pattern of positively accelerated responding during fixed interval was changed to a linear pattern when response-independent reinforcement occurred under a variable-time schedule. Overall response rates (total responses/total time) decreased as the frequency of response-independent reinforcement increased. Experiment II showed that the response-rate changes in the first experiment were controlled by the response-reinforcer relation, but the changes in patterns of responding were similar whether concurrently available reinforcement at varying times was response-dependent or response-independent. In the final experiment, the addition of response-independent reinforcement at fixed times to a fixed-interval schedule resulted in changes in both local and overall response rates and in the occurrence of positively accelerated responding between reinforcements. These results suggest that the temporal distribution of reinforcers determines response patterns and that both the response-reinforcement dependency and the schedule of reinforcement determine overall response rates during concurrently scheduled response-dependent and response-independent reinforcement.     

Timeout from a stimulus correlated with the extinction component of a multiple schedule

Four groups of pigeons were trained to discriminate between green and red. Pecks on a second key produced a timeout from the schedule in effect for 30 sec. For two of the groups, this timeout response turned off all the lights in the chamber (Blackout), while for the other two, only the key-lights were turned off (No Blackout). For one of the Blackout groups and one of the No Blackout groups, responses on the discrimination key during the extinction component (S^?) also resulted in a mild electric shock. Blackout groups produced more timeouts during S^? than did No Blackout groups, but electric shock punishment suppressed, rather than enhanced, timeout responding. These findings suggest a need for reevaluation of the hypothesis that the timeout response is an escape from an aversive S^?.     

Stimulus generalization and delay of reinforcement during one component of a multiple schedule

The key pecking of six pigeons was reinforced according to a variable-interval 1-min schedule during each of two successively presented stimuli. When the key was illuminated by a black line on a white background, reinforcement was delayed for 10 sec. When the key was illuminated by a plain white light, reinforcement was not delayed. All subjects responded at a lower rate during the presentation of the black line. A subsequent generalization test along the line-orientation dimension produced a U-shaped gradient, with the nadir located at or near the training stimulus, for each subject. These gradients suggested that the lower rate of response during the stimulus associated with delayed reinforcement may have been due to an inhibition of responding.     

The effects of unavoidable shocks on a multiple schedule having an avoidance component

Two dogs were maintained on a multiple schedule having both a food reinforced and an avoidance component (Mult VI 1′ S^Δ Avoid_{SS20 RS20} S^Δ). The effects of superimposing an Estes-Skinner procedure for delivering unavoidable shocks on all components of the multiple schedule were observed. The buzzer-shock pairing of the Estes-Skinner procedure produced an increased rate of responding on the avoidance component of the schedule and also on the S^Δ components. No persistent change in rate was observed on the food component during the pre-shock stimulus. Control performances on all components could be regained by either extinguishing or eliminating the buzzer-shock pairing. Extinction of the avoidance responding had little effect on the increased rates of responding produced by the Estes-Skinner procedure on the S^Δ and avoidance extinction components and did not lead to a conditioned suppression of the food reinforced responding. Rate of responding during the pre-shock stimulus was observed to be relatively independent of changes in the maintaining schedules. Responding during the pre-shock stimulus could be conditioned and maintained after an extensive history of avoidance extinction.     

Behavioral contrast in one component of a multiple schedule as a function of the reinforcement conditions operating in the following component

The key pecks of four pigeons were reinforced on a variable-interval 5-min schedule which operated in each of the four components of a multiple schedule, indicated by red, green, yellow, and blue stimuli and presented in such an order that the red stimulus always preceded the yellow and the green stimulus always preceded the blue. After establishing baseline rates, the reinforcement schedule associated with the blue and yellow components was altered so that one was now an extinction schedule and the other was a variable-interval 1-min schedule. In a second experimental stage, the blue stimulus was interchanged with the yellow so that the red stimulus preceded the blue and the green stimulus preceded the yellow. In both experimental stages the response rate in the variable-interval 5-min component that preceded the extinction component was higher than the response rate in the variable-interval 5-min component that preceded the variable-interval 1-min component. The results were discussed in relation to the importance of stimulus ordering in experiments concerned with investigating behavioral contrast.     

An evaluation of a three‐component multiple schedule to indicate attention availability

Students may engage in high rates of social approach responses at inappropriate times throughout the school day. One intervention that has been used to teach students appropriate and inappropriate times to access attention is a multiple schedule of reinforcement. In this study, we evaluated the efficacy of a multiple schedule that indicated when attention was available or not available in a bilingual preschool classroom during small‐group instruction. Results showed that the intervention was effective in bringing students’ social approaches under stimulus control.     

Delayed reinforcement in a multiple schedule

Three rats and a pigeon were first trained on a two-component multiple schedule in which reinforcement in the two components occurred immediately after a response. Later, reinforcement in one component was delayed by a few seconds. During both stages of the experiment, reinforcement was scheduled by equal variable- (pigeon) or random-interval (rats) schedules in the two components. The main effect of the delayed reinforcement was to increase the rate of responding in the unchanged (non-delay) component. This behavioral contrast effect did not appear in all cases to be dependent upon a reduction in the rate of responding or the frequency of reinforcement in the delay component. This finding suggests that a reduction in response rate and/or reinforcement frequency in one component of a multiple schedule may not be a necessary prerequisite for the occurrence of behavioral contrast. This finding is, however, consistent with an explanation that suggests that behavioral contrast results from the introduction of a less-preferred condition in one component of a multiple schedule, since it is known that animals “prefer” immediate to delayed reinforcement.     

Hunger and contrast in a multiple schedule

Pigeons working for food on a multiple variable-interval 1-min-variable-interval 4-min schedule were subjected to variations in body weight, presumably causing changes in hunger. The proportion of responses in each component approached and eventually reached the proportion of reinforcements as body weight increased. This effect follows from the matching-law interpretation of contrast in multiple schedules.     

Development of a complex multiple schedule in the chimpanzee

The development of chimpanzee behavior on a four-component, three-lever multiple schedule is described. Component schedules included the Sidman avoidance procedure with a concurrent discriminated avoidance schedule on a second lever, fixed ratio performance for food, differential reinforcement of low rate for water requiring a dual response chain, and a symbol discrimination task for continuous food reinforcement using three levers. The avoidance component of this schedule was employed during the January 31, 1961 suborbital space flight of the chimpanzee “Ham.” On November 29, 1961, the chimpanzee “Enos” performed on the multiple schedule during three orbits around the earth in a Mercury capsule.     

Behaviour of rats in multiple schedules of response-contingent and response-independent food presentation

During Phase I, three rats were exposed to two-component multiple schedules of response-independent food presentation. Low rates of lever-pressing were observed, and response rates in one component did not increase when food presentation was withheld in the other component. During Phase II, the same rats were exposed to two-component multiple schedules of response-contingent reinforcement. Much higher rates of lever-pressing were observed. Moreover, when reinforcement was withheld in one component, response rates in the other component increased (positive contrast), and when reinforcement was reinstated in the changed component, response rates in the other component declined (negative contrast). During Phase III, when food was again delivered independently of responding, the response rates declined again to low levels. These results indicate that the occurrence of non-instrumental lever-pressing is not a prerequisite for the occurrence of behavioural contrast in the rat, and thus cast doubt on the general applicability of the autoshaping theory of behavioural contrast     

Observing responses in pigeons: effects of schedule component duration and schedule value

Pigeons were exposed to a procedure under which five pecks on one response key (the observing key) changed the schedule on a second key (the food key) from a mixed schedule to a multiple schedule for 25 sec. In Experiment I, a random-ratio 50 schedule alternated with extinction. The duration of the random-ratio 50 schedule component was varied between 1.25 and 320 sec, and extinction was scheduled for a varying time, ranging from the duration of the random-ratio 50 to four times that value. Each set of values was scheduled for a block of sessions. Before observing-key pecks were allowed at each set of parameter values, the pigeons were exposed to a condition where the mixed and multiple schedule alternated every 10 min, and observing-key pecks were not permitted. Rates of pecking on the observing key were high for all values of random-ratio component durations except 1.25 sec. Experiment II was conducted with the random-ratio component duration equal to 40 sec, and the random-ratio schedule was varied from random-ratio 50 to 100, 200, and 400. Observing-key pecking rates were high for all values of the random-ratio schedule except random-ratio 400. In both experiments, observing response rates were relatively little affected, suggesting that neither schedule component duration nor schedule value is a strong determinant of observing responses.     

Time-dependent contrast effects in a multiple schedule of food reinforcement

Four rats were rewarded for running in a wheel under two alternating conditions of food reinforcement. These periods of frequent and infrequent reinforcement, each accompanied by a particular stimulus, were presented a number of times in each daily session. Following shifts from high to low frequency of reinforcement, responding decreased suddenly and markedly, and then recovered within the next few minutes. The magnitude of this temporary depression was an increasing function of the duration of the immediately preceding component of high-frequency reinforcement. A transient elevation in performance, which did not vary with the duration of the prior component, was noted in two subjects following shifts from low to high frequency of reinforcement. The elevation and depression effects did not appear simultaneously during the 48 experimental sessions. A possible relation between the difficulty of the discrimination and the extent of contrast effects is discussed.     

Pavlovian contingencies and resistance to change in a multiple schedule

According to theoretical accounts of behavioral momentum, the Pavlovian stimulus—reinforcer contingency determines resistance to change. To assess this prediction, 8 pigeons were exposed to an unsignaled delay-of-reinforcement schedule (a tandem variable-interval fixed-time schedule), a signaled delay-of-reinforcement schedule (a chain variable-interval fixed-time schedule), and an immediate, zero-delay schedule of reinforcement in a three-component multiple schedule. The unsignaled delay and signaled delay schedules employed equal fixed-time delays, with the only difference being a stimulus change in the signaled delay schedule. Overall rates of reinforcement were equated for the three schedules. The Pavlovian contingency was identical for the unsignaled and immediate schedules, and response—reinforcer contiguity was degraded for the unsignaled schedule. Results from two disruption procedures (prefeeding subjects prior to experimental sessions and adding a variable-time schedule to timeout periods separating baseline components) demonstrated that response—reinforcer contiguity does play a role in determining resistance to change. The results from the extinction manipulation were not as clear. Responding in the unsignaled delay component was consistently less resistant to change than was responding in both the immediate and presignaled segments of the signaled delay components, contrary to the view that Pavlovian contingencies determine resistance to change. Probe tests further supported the resistance-to-change results, indicating consistency between resistance to change and preference, both of which are putative measures of response strength.