Recency, repeatability, and reinforcer retrenchment: an experimental analysis of resurgence

Four experiments were conducted with pigeons to assess the experimental conditions necessary for the occurrence of resurgence. The general procedure consisted of the following conditions: Condition 1--reinforcement of key pecking; Condition 2--reinforcement of treadle pressing and concurrent extinction of key pecking; and Condition 3--the resurgence condition wherein resurgence was defined as the recovery of key pecking. In Experiments 1 and 2, the resurgence condition was conventional extinction. The effect of recency on resurgence magnitude was examined in Experiment 1 by manipulating the number of sessions of Condition 2, above. Resurgence was not a function of recency with the parameters used. Repeating the three conditions revealed resurgence to be a repeatable effect in Experiment 2. In Experiment 3, a variable-time schedule was in effect for the resurgence condition. Resurgence was not produced by response-independent food delivery. In Experiment 4, the resurgence condition was a variable-interval schedule for treadle pressing that arranged a lower reinforcement rate than in Condition 2 (92% reduction in reinforcers per minute). Resurgence was lower in magnitude relative to conventional extinction, although resurgence was obtained with 2 out of 3 pigeons. The results are discussed in terms of the variables controlling resurgence and the relations between behavioral history, resurgence, and other forms of response recovery.     

Trial and intertrial durations in Pavlovian conditioning: issues of learning and performance

Four experiments assessed the effects of trial (T) and intertrial (I) durations on magazine approach behavior in rats. In Experiments 1 and 2, different groups of animals were conditioned with various combinations of I and T durations. The rate of acquisition, in terms of the number of trials required to reach various acquisition criteria, generally was faster in groups trained with large I:T ratios. There also were differences in rate of acquisition and terminal response rates between groups trained with identical I:T ratios but with different absolute I and T durations. Differences evident at the end of conditioning persisted during a common test with various combinations of I and T durations. Experiments 3 and 4 provided a more specific test of the predictions of 2 general classes of theories and found results that were consistent with those theories that characterize group differences as indicative of differences in learning, rather than in performance.     

Reward Density And Variable-interval Schedule Performance In An Open Economy

There is no general agreement regarding the form of the relation between response rate and reinforcement rate when single schedules of reinforcement are studied in an open economy. The present study assessed the form of this relation using reward density, which incorporates both reinforcement rate and duration of access to food, as an independent variable. Reward density was manipulated with 4 pigeons by changing the value of the variable-interval schedule, the hopper duration, or both. The relations between response rate and reward density were sharply rising and hyperbolic in 3 of 4 pigeons, replicating results obtained by Catania and Reynolds (1968). Because eating efficiency was lower in conditions that provided longer hopper durations, programmed reward densities differed from obtained reward densities. When response rates were examined as a function of obtained reward densities, the same relations were demonstrated more strongly. In further clarifying the relation between response rate and reward density in an open economy, these results lend support to the conclusion that open and closed economies yield different behavioral effects.     

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.     

Some effects of response independent reinforcers in multiple schedules

In Exp. I, rats' lever presses were conditioned on multiple variable-interval variable-interval schedules. Changing one of the multiple schedule components to variable time reduced responding in that component. Further reductions in responding occurred in both components when the schedule was changed to multiple variable-time variable-time. After reinstating the multiple variable-interval variable-time schedule, lower response rates were maintained in the variable-time component during a series of stimulus reversals. In Exp. II, replacement of extinction components of multiple variable-interval extinction or multiple extinction extinction with variable-time schedules for single sessions (probe) resulted in response rate increments in those components. In the former schedule these increases were concomitant with response decreases during the variable-interval components. Response increases in the variable-time probes were related to conditioning history and, as a result, to response probability at the time of the probe.