Generalization of the disruptive effects of alternative stimuli when combined with target stimuli in extinction.

Differential-reinforcement treatments reduce target problem behavior in the short term but at the expense of making it more persistent long term. Basic and translational research based on behavioral momentum theory suggests that combining features of stimuli governing an alternative response with the stimuli governing target responding could make target responding less persistent. However, changes to the alternative stimulus context when combining alternative and target stimuli could diminish the effectiveness of the alternative stimulus in reducing target responding. In an animal model with pigeons, the present study reinforced responding in the presence of target and alternative stimuli. When combining the alternative and target stimuli during extinction, we altered the alternative stimulus through changes in line orientation. We found that (1) combining alternative and target stimuli in extinction more effectively decreased target responding than presenting the target stimulus on its own; (2) combining these stimuli was more effective in decreasing target responding trained with lower reinforcement rates; and (3) changing the alternative stimulus reduced its effectiveness when it was combined with the target stimulus. Therefore, changing alternative stimuli (e.g., therapist, clinical setting) during behavioral treatments that combine alternative and target stimuli could reduce the effectiveness of those treatments in disrupting problem behavior.

Training reinforcement rates, resistance to extinction, and the role of context in reinstatement.

Behavior reduced as a consequence of extinction or intervention can relapse. According to behavioral momentum theory, the extent to which behavior persists and relapses once it has been eliminated depends on the relative training reinforcement rate among discriminative stimuli. In addition, studies of context renewal reveal that relapse depends on the similarity between the training stimulus context and the test stimulus context following disruption by extinction. In the present experiments with pigeons, we arranged different reinforcement rates in the presence of distinct discriminative stimuli across components of a multiple schedule. Following extinction, we attempted to reinstate responding in the presence of those target components with response-independent food presentations. Importantly, we arranged the reinstating food presentations either within the target components or in separate components, either paired with extinction (Experiment 1) or reinforcement (Experiment 2) during baseline. Reinstatement increased with greater training reinforcement rates when the reinstating food presentations were arranged in the target components and the separate components paired with reinforcement during training. Reinstatement was smaller and was not systematically related to training reinforcement rates in the target components when reinstating food presentation occurred in separate components paired with extinction. These findings suggest that relapse depends on the history of reinforcement associated with the discriminative stimuli in which the relapse-inducing event occurs.

Stimulus generalization and operant context renewal.

Context renewal is the relapse of an extinguished response due to changing the stimulus context following extinction. Reinforcing operant responding in Context A and extinguishing in Context B results in relapse when either returning to Context A (ABA renewal) or introducing a novel Context C (ABC renewal). ABA renewal typically is greater than ABC renewal. The present study assessed whether renewal might be conceptualized through excitatory and inhibitory generalization gradients inferred from studies of stimulus generalization. We arranged one keylight-color alternation frequency for pigeons to signal reinforcement in Phase 1 and a different alternation frequency to signal extinction in Phase 2. During a subsequent test in extinction, we presented a range of keylight-alternation frequencies and found renewal to be a function of keylight-alternation frequency. Specifically, Phase-3 responding increased as keylight-alternation frequency differed from that arranged during extinction in Phase 2. Moreover, we observed a shift in the function beyond the originally reinforced keylight-alternation frequency arranged in training (i.e., peak shift). We discuss the relevance of these findings for conceptualizing stimulus-control processes governing generalization gradients for understanding the processes underlying context renewal.

Choice, time and food: continuous cyclical changes in food probability between reinforcers.

The current experiment examined the degree to which locally varying food probabilities on two keys across time since food presentations can continue to control choice until the next food delivery. In two sets of conditions, the probability of food delivery being made available on one key relative to the other key varied sinusoidally across a 1-min period following each food delivery. In Set 1, food-probability changes were unsignaled and the number of cycles per min was varied across conditions. In Set 2, there were always two complete cycles of the sinusoid in the 1-min period, and brief key-color changes were arranged at a selection of fixed times since food delivery to signal portions of the sinusoid. In Set 1, control of choice by local probability of food on each key decreased over time since food delivery. Control by local food probabilities was greater in conditions that arranged fewer cycles per min. The onset of stimulus changes in Set 2 led to a transient reinstatement of local control by food probabilities regardless of the portion of the sinusoidal variation in food probabilities signaled by the stimuli. However, in conditions where the same colored stimuli signaled different portions of the sinusoidal variation in food-delivery probabilities, stimulus changes attenuated joint control by elapsed time and food-probability values. These results suggest that, changing relative food probabilities and stimuli can direct preference toward the likely location of the next food delivery across time since a food presentation, although the degree to which control over choice will be maintained across elapsed time depends on how experimenter-arranged contingencies are mapped onto elapsed time.