Showing papers by "Timothy A. Shahan published in 2018"

Suboptimal choice, reward-predictive signals, and temporal information.

Abstract: Suboptimal choice refers to preference for an alternative offering a low probability of food (suboptimal alternative) over an alternative offering a higher probability of food (optimal alternative). Numerous studies have found that stimuli signaling probabilistic food play a critical role in the development and maintenance of suboptimal choice. However, there is still much debate about how to characterize how these stimuli influence suboptimal choice. There is substantial evidence that the temporal information conveyed by a food-predictive signal governs its function as both a Pavlovian conditioned stimulus and as an instrumental conditioned reinforcer. Thus, we explore the possibility that food-predictive signals influence suboptimal choice via the temporal information they convey. Application of this temporal information-theoretic approach to suboptimal choice provides a formal, quantitative framework that describes how food-predictive signals influence suboptimal choice in a manner consistent with related phenomena in Pavlovian conditioning and conditioned reinforcement. Our reanalysis of previous data on suboptimal choice suggests that, generally speaking, preference in the suboptimal choice procedure tracks relative temporal information conveyed by food-predictive signals for the suboptimal and optimal alternatives. The model suggests that suboptimal choice develops when the food-predictive signal for the suboptimal alternative conveys more temporal information than that for the optimal alternative. Finally, incorporating a role for competition between temporal information provided by food-predictive signals and relative primary reinforcement rate provides a reasonable account of existing data on suboptimal choice. (PsycINFO Database Record

Punishment of an alternative behavior generates resurgence of a previously extinguished target behavior.

Abstract: Resurgence is often defined as the recurrence of an extinguished behavior when a more recently reinforced alternative behavior is also extinguished. Resurgence has also been observed when the alternative behavior is devalued by other means (e.g., reinforcement rate or magnitude reductions). The present study investigated whether punishment of an alternative behavior would generate resurgence. A target response was reinforced during Phase 1 and then extinguished in Phase 2 while an alternative response was reinforced. During Phase 3, response-dependent foot shocks were superimposed on the schedule of reinforcement for the alternative response and shock intensity was escalated gradually across sessions. Resurgence of the target response was reliably observed, mostly at higher intensities. The effect was replicated in two subsequent exposures to the sequence of conditions, with resurgence tending to occur at the lowest foot shock intensity. These results suggest that devaluation of an alternative behavior via punishment can generate resurgence. Although it is difficult to reconcile the overall pattern of results with Bouton's context account, these findings are consistent with the suggestion that resurgence results from a "worsening of conditions" for the alternative behavior and with the formalization of that suggestion in terms of a choice-based matching-law account (i.e., Resurgence as Choice).

Delivering alternative reinforcement in a distinct context reduces its counter-therapeutic effects on relapse

Abstract: Delivery of alternative reinforcers in the presence of stimuli previously associated with reinforcement for target behavior increases the susceptibility of target behavior to relapse. To explore contingencies that might mitigate this counter-therapeutic effect, we trained pigeons on a procedure that entailed extinction of previously reinforced target-key pecking, access to a distinct stimulus context contingently on refraining from target behavior (differential-reinforcement-of-other-behavior; DRO), and reinforcement of alternative-key pecks (differential-reinforcement of alternative behavior; DRA) in that context. This DRO-DRA treatment was compared with standard DRA in successive conditions, counterbalanced across pigeons. Target behavior extinguished more rapidly in the Standard-DRA condition. When alternative reinforcement was discontinued, however, there was less resurgence after DRO-DRA than after Standard DRA. In a third condition, the DRO contingency was suspended so that the former DRA stimuli were not presented (DRO-NAC), and resurgence was greater than in the Standard-DRA and DRO-DRA conditions. Reinstatement produced by response-independent reinforcers was small and similar across conditions. Subsequent reacquisition of target-key pecking under baseline reinforcement conditions was faster following DRO-NAC than Standard-DRA or DRO-DRA. These findings suggest that DRO-DRA might serve as a useful method in clinical settings for reducing problem behavior while minimizing the threat of posttreatment relapse.

Renewal of extinguished operant behavior following changes in social context.

Abstract: Renewal is the reoccurrence of previously extinguished behavior following a change in the context in which extinction was conducted. Despite an extensive body of research examining renewal, little is known about the role of social stimuli in renewal. The present experiments provided a novel examination of renewal of operant behavior by changing social stimuli across phases in an ABA renewal preparation. In both experiments, social stimuli were arranged by placing another rat in a second compartment of a divided operant chamber. In Experiment 1, the presence of another rat defined the extinction context, whereas an empty second compartment defined the baseline and testing contexts. We reversed these contextual manipulations in Experiment 2 such that the presence of another rat defined the baseline and testing contexts and the second compartment was empty during extinction. Renewal of lever pressing occurred when the other rat was removed from the chamber in Experiment 1 and when the other rat was returned to the chamber in Experiment 2. Thus, social stimuli may function as contextual stimuli, and changes in social contexts may produce renewal of previously extinguished behavior.

Multiple schedules, off-baseline reinforcement shifts, and resistance to extinction.

Abstract: Resistance to extinction in a target multiple-schedule component varies inversely with the rate of reinforcement arranged in an alternative component during baseline. The present experiment asked whether changing the reinforcer rate in an alternative component would impact extinction of target component responding if those changes occurred in an off-baseline phase during which the target component was never experienced. Pigeons' key pecking was studied in three types of conditions, and each condition consisted of three phases. In Phase 1, pecking produced food in the target and alternative components of a multiple schedule according to variable-interval 60-s schedules. In Phase 2, the alternative-component stimulus was presented alone in a single schedule. Pecking during this phase produced the same reinforcer rate as in baseline in the Control condition, a higher rate of food (variable-interval 15 s) in the High-Rate condition, or was extinguished in the Extinction condition. Extinction of target- and alternative-component key pecking then was assessed in a multiple schedule during the final phase of each condition. Resistance to extinction of target-component key pecking was the same between the Control and High-Rate conditions but lower in the Extinction condition. These findings are discussed in terms of discrimination and generalization processes.