Choice with probabilistic reinforcement: effects of delay and conditioned reinforcers.

Two experiments measured pigeons' choices between probabilistic reinforcers and certain but delayed reinforcers. In Experiment 1, a peck on a red key led to a 5-s delay and then a possible reinforcer (with a probability of .2). A peck on a green key led to a certain reinforcer after an adjusting delay. This delay was adjusted over trials so as to estimate an indifference point, or a duration at which the two alternatives were chosen about equally often. In all conditions, red houselights were present during the 5-s delay on reinforced trials with the probabilistic alternative, but the houselight colors on nonreinforced trials differed across conditions. Subjects showed a stronger preference for the probabilistic alternative when the houselights were a different color (white or blue) during the delay on nonreinforced trials than when they were red on both reinforced and nonreinforced trials. These results supported the hypothesis that the value or effectiveness of a probabilistic reinforcer is inversely related to the cumulative time per reinforcer spent in the presence of stimuli associated with the probabilistic alternative. Experiment 2 tested some quantitative versions of this hypothesis by varying the delay for the probabilistic alternative (either 0 s or 2 s) and the probability of reinforcement (from .1 to 1.0). The results were best described by an equation that took into account both the cumulative durations of stimuli associated with the probabilistic reinforcer and the variability in these durations from one reinforcer to the next.     

Effects of search cost on foraging and feeding: a three-component chain analysis

An experiment determined whether pigeons minimize number of key pecks per food delivery and maintain their baseline intake of food while key pecking on a three-component chain schedule. Pigeons at either 80% or 100% body weight obtained all their food during baseline and contingency sessions. During baseline sessions, pecks on the left and center keys had no consequences; each peck on the right key activated the feeder. During contingency sessions, pigeons key pecked on a three-component chain schedule simulating components of a foraging chain. In the search component either 3, 9 or 15 key pecks (varied parametrically across blocks of sessions) on the left key produced a stimulus on the middle key, indicating an encounter with either the low-cost prey (3 key pecks) or an equally probable high-cost prey (21 key pecks). In the procurement component the pigeon pecked either: (a) the left key once, thus returning to the search component, or (b) the middle key either 3 or 21 times, which activated the right response key. In the handling component one peck on the right key operated the feeder. The pigeons always procured the low-cost prey and minimized the number of key pecks per hopper by procuring the high-cost prey when the search-cost ratio was high (15 key pecks) but not when it was low (3 key pecks). All pigeons maintained their baselines of eating during contingency sessions by key pecking more frequently and eating more efficiently. The 80% body-weight birds produced higher overall rates of key pecking and eating. These results have implications for ecological theories of optimal foraging and for psychological theories of learned performance.     

Escalating schedules of incentives increase physical activity with no differences between deposit and no-deposit groups: A systematic replication

Physical inactivity has increasingly affected public health in the United States during the COVID-19 pandemic as it is associated with chronic diseases such as arthritis, cancer, and heart disease. Contingency management has been shown to increase physical activity. Therefore, the present study sought to evaluate the effects of an escalating schedule of monetary reinforcement with a reset contingency on physical activity, as compared between 2 counterbalanced groups in which a monetary deposit of $25 was either required (deposit group) or not (no-deposit group). Twenty-five adults wore Fitbit accelerometers to monitor step counts. An ABA reversal design was used; in the 2 baseline phases, no programmed contingencies were in place for step counts. During intervention, step goals were set using a modified 70^th percentile schedule with a 7-day window: Reaching the first goal would result in $0.25, and incentives increased by $0.25 for each subsequent day in which the goal was met. Failure to reach a goal resulted in a reset of the monetary incentive value to $0.25. Ten out of 12 participants from the deposit group were determined to be responders to intervention, whereas 8 out of 13 participants from the no-deposit group were determined to be responders to intervention. Overall, there were no significant differences between the groups' step counts. However, the deposit group's intervention was cheaper to implement, which suggests that deposit contracts are a viable modification for physical activity interventions.     

Toward an empirical method for identifying matched stimulation for automatically reinforced behavior: a preliminary investigation

The effects of noncontingent matched stimulation (NMS) and response blocking on a boy's stereotypic behavior were evaluated using a multiple schedule that contained three 15-min components (preintervention, intervention, and postintervention). Results showed that stereotypy was always higher after response blocking than before response blocking and was always lower after NMS than before NMS. These results suggest that response blocking may have produced deprivation for the product of stereotypy and that NMS may have provided stimulation that was similar to the product of stereotypy.     

Roger T. Kelleher, behavior analyst

Roger T. Kelleher, rightly known as one of the foremost contributors to behavioral pharmacology, also made many important contributions to the experimental analysis of behavior. He participated significantly in the development of the discipline, through both his research and his editorial contributions to thisjournal. This article summarizes his contributions to the field of behavior analysis. His most significant empirical and conceptual contributions to behavior analysis came in two domains-conditioned reinforcement and the power of schedules of reinforcement. His accomplishments in these two domains still serve as principal foundations for modern research and theory.     

Tolerance to the effects of cocaine on performance under behavior-correlated reinforcement magnitude

Four pigeons responded under a fixed-interval 8-min schedule of food delivery in which the amount of food delivered at the end of each interval depended on performance during the interval (i.e., a correlated schedule). Specifically, duration of access to grain was contingent upon the number of responses made during the first 4 min of the interval. This differential outcome did not affect response rates or patterning relative to performance under a simple fixed-interval 8-min schedule. Behavior under the correlated schedule was then investigated under doses of cocaine ranging from 0.3 to 10.0 mg/kg. A bitonic dose-response function was obtained for response rates and the time with head in the food hopper, whereas dose-dependent decreases were observed in the mathematical index of curvature (Fry, Kelleher, & Cook, 1960). The dose that produced the greatest increase in the head-in-hopper time was then administered prior to each session. Following repeated administration of cocaine, disruptions in response patterning were attenuated for all 4 pigeons; tolerance was also observed to the rate-increasing effects and increased head-in-hopper time for 2 pigeons after chronic cocaine administration. Tolerance therefore developed despite the fact that the initial effect of cocaine was to increase the amount of food obtained.     

Matching theory and induction explain operant performance

Matching theory is a general framework for understanding allocation of behavior among activities. It applies to choice in concurrent schedules and was extended to single schedules by assuming that other unrecorded behavior competes with operant behavior. Baum and Davison (2014) found that the competing activities apparently are induced by the “reinforcers” (phylogenetically important events, e.g., food) according to power functions. Combined with power-function induction, matching theory provides new equations with greater explanatory power. Four pigeons were exposed to conditions in which 7 different schedules of food delivery were presented within each experimental session. We replicated earlier results with variable-interval schedules: (a) a negatively accelerated increase of peck rate as food rate increased in the low range of food rates; (b) an upturn in pecking at higher rates; and (c) a downturn in pecking at extremely high food rates. When the contingency between pecking and food was removed, the food continued to induce pecking, even after 20 sessions with no contingency. A ratio schedule inserted in place of 1 variable-interval schedule maintained peck rates comparable to peck rates maintained by short interval schedules. We explained the results by fitting equations that combined matching theory, competition, and induction.     

The multiple-stimulus-without-replacement preference assessment tool and its predictive validity

This study demonstrates the use of two web-based programs, one to identify video preferences and the other to assess their reinforcing effects. We used the Multiple-Stimulus-Without-Replacement Preference Assessment Tool (MSWO PAT) to identify the video preference hierarchies of seven participants, ages 4–11 years old. We then used a customized reinforcer assessment program that arranged a concurrent-chains preparation with programmed conjugate schedules of reinforcement. Button presses emitted by participants modulated the quality (volume and opacity) of selected videos on a moment-to-moment basis, allowing us to identify the reinforcing effects of the videos in little time. The results showed that the preference assessment had predictive value for five of seven participants. We discuss the MSWO PAT, parameters that may affect the identification of preferences and the use of conjugate schedules to identify reinforcers.