Systematic Review of Differential Reinforcement in Skill Acquisition.

The purpose of this article was to review and summarize the literature investigating the impact of differential reinforcement on skill acquisition. Researchers synthesized data from 10 articles across the following categories: (1) participant characteristics; (2) setting; (3) reinforcement procedures; (4) within-subject replication; (5) results; and (6) secondary measures (e.g., social validity). Results indicated that most of the participants were male, had a diagnosis of autism, and communicated vocally. The differential reinforcement condition in which reinforcement favored independent responses (e.g., edible for independent; praise for prompted responses) was the most frequently employed differential reinforcement condition and it resulted in the acquisition of more responses or faster acquisition for most participants. In addition, when differing reinforcement procedures manipulating different parameters of reinforcements were compared, better outcomes were attained when the schedule of the reinforcer was manipulated within the differential reinforcement procedure relative to when quality or magnitude were manipulated. Limitations of the previous research, recommendations for future research, and implications for clinical practice are discussed.

Development and Validation of an Assessment-Driven Behavioral Intervention for Primary Complex Motor Stereotypies in Young Children.

Complex motor stereotypies are rhythmic, repetitive, fixed, and non-goal directed movements (e.g., bilateral flapping/waving movements of the hands/arms). Movements typically begin in early childhood and can occur in otherwise normally developing ("primary") or autistic ("secondary") children. Stereotypies persist, occur multiple times a day, have prolonged durations, can be socially stigmatizing, and may lead to bullying and isolation. Prior behavioral treatment studies have focused on older children (ages 6-12) and report modest reductions in stereotypy (i.e., between 14% and 33%). The current study involves the functional assessment and treatment of five children with Primary Complex Motor Stereotypy using a modified awareness training procedure, differential reinforcement of other behavior, and schedule thinning in a nonconcurrent multiple baseline design. Results suggest a 99% reduction of motor stereotypy from baseline across all participants.

The neuropharmacological profile of interval responding during operant tasks.

Responses occurring during intervals of operant tasks have been subdivided as interim, facultative, and terminal, depending on the time between response onset and reward. Although interval responses, also known as adjunctive responses, have been described in pigeons, rats, mice, monkeys, and humans, most experiments have been conducted in rats. We review the neurochemical basis of interval responses and examine the hypothesis that these responses modulate operant performance. Preliminary experiments indicate the involvement of biogenic amines, acetylcholine, and GABA during interval responding associated with operant tasks. In particular, catecholaminergic deafferentation of the basal ganglia modulated interval responses as did the peripheral injection of catecholamine reuptake blockers. Under the influence of amphetamine, interval responding may either increase or decrease, so that a wide range of responses must be selected to gauge drug effects. In non-drugged pigeons and rats, the expression of interval responses facilitates operant training.

Resurgence of ethanol seeking following voluntary abstinence produced by nondrug differential reinforcement of other behavior.

Resurgence refers to the relapse of a target behavior following the worsening of a source of alternative reinforcement that was made available during response elimination. Most laboratory analyses of resurgence have used a combination of extinction and alternative reinforcement to reduce target behavior. In contingency-management treatments for alcohol use disorder, however, alcohol use is not placed on extinction. Instead, participants voluntarily abstain from alcohol use to access nondrug alternative reinforcers. Inasmuch, additional laboratory research on resurgence following voluntary abstinence is warranted. The present experiment evaluated resurgence of rats' ethanol seeking following voluntary abstinence produced by differential reinforcement of other behavior (DRO). Lever pressing produced ethanol reinforcers during baseline phases. During DRO phases, lever pressing continued to produce ethanol and food reinforcers were delivered according to resetting DRO schedules. Ethanol and food reinforcers were suspended during resurgence test phases to evaluate resurgence following voluntary abstinence. Lever pressing was elevated during baseline phases and occurred at near-zero rates during DRO phases. During the resurgence test phases, lever pressing increased, despite that it no longer produced ethanol. The procedure introduced here may help researchers better understand the variables that affect voluntary abstinence from ethanol seeking and resurgence following voluntary abstinence.

Evaluating Preference for Functional and Nonfunctional Stimuli in the Treatment of Destructive Behavior.

The effects of including nonfunctional stimuli that may appear in the natural environment during treatment remain unclear. The current study evaluated preference for differential reinforcement of communication (DRC) treatments with functional reinforcers only and a combination of functional and nonfunctional stimuli. Both treatment conditions resulted in a decrease in destructive behavior and an increase in the communication response for all participants. Two participants preferred the combined DRC condition, whereas one participant showed equal preference for the combined condition and one of the functional conditions.

Differential Reinforcement of Low Frequency Behavior as an Interdependent Group Contingency for Children Diagnosed with Autism Spectrum Disorder.

An ABAB reversal design was employed to evaluate the effect of differential reinforcement of low (DRL) frequency behavior as an interdependent group contingency on the frequency of vocal disruptions of five males, 6-14-years old, diagnosed with an autism spectrum disorder. The results showed lower frequencies of vocal disruptions during intervention conditions as compared to baseline conditions; the combination of DRL and interdependent group contingency was effective at reducing the target behavior from baseline levels. Implications of concurrent interventions for the applied setting are discussed.

Concurrent schedules of differential reinforcement of alternative behavior in the treatment of problem behavior without extinction.

Differential reinforcement of alternative behavior (DRA) without extinction is an effective intervention for reducing problem behavior maintained by socially mediated reinforcement, particularly when implementing dense schedules of reinforcement for appropriate behavior. Thinning schedules of reinforcement for an alternative response may result in resurgence of problem behavior. Resurgence may be of particular concern in the treatment of problem behavior without extinction because problem behavior that resurges is also likely to encounter reinforcement and thus can be expected to maintain. In the present investigation, we compared the effectiveness of single and concurrent DRA schedules in decreasing the probability of resurgence when problem behavior continues to produce reinforcement throughout all phases of the evaluation. Concurrent DRA schedules reduced or eliminated the likelihood of resurgence compared with a single DRA schedule during a treatment challenge.

Operant ABA renewal during dense and lean schedules of differential reinforcement.

Renewal is a type of relapse that occurs due to a change in context. Previous research has demonstrated that renewal of target responding may occur despite the availability of differential reinforcement for an alternative response (DRA). Nevertheless, the current literature on renewal presents mixed findings regarding the effects of dense and lean schedules of DRA on the magnitude of renewal. We used a translational approach with undergraduate college students and a task on a touchscreen tablet device to study the effects of dense and lean schedules of DRA during repeated renewal tests. All participants experienced two, three-phase ABA renewal arrangements. In the dense and lean renewal arrangements, we differentially reinforced alternative behavior in Context B and the renewal test in Context A on a VI 3-s or a VI 12-s schedule, respectively. Overall, we observed renewal in 31/36 (86%) renewal tests regardless of the density of reinforcement for the alternative response. Furthermore, the results showed that although renewal occurred in both arrangements, we found slightly higher magnitudes of renewal during DRA with lean schedules of reinforcement relative to dense schedules. We discuss the implications of these findings as they relate to the treatment of problem behavior.

Modeling VI and VDRL feedback functions: Searching normative rules through computational simulation.

We present the mathematical description of feedback functions of variable interval and variable differential reinforcement of low rates as functions of schedule size only. These results were obtained using an R script named Beak, which was built to simulate rates of behavior interacting with simple schedules of reinforcement. Using Beak, we have simulated data that allow an assessment of different reinforcement feedback functions. This was made with unparalleled precision, as simulations provide huge samples of data and, more importantly, simulated behavior is not changed by the reinforcement it produces. Therefore, we can vary response rates systematically. We've compared different reinforcement feedback functions for random interval schedules, using the following criteria: meaning, precision, parsimony, and generality. Our results indicate that the best feedback function for the random interval schedule was published by Baum (1981). We also propose that the model used by Killeen (1975) is a viable feedback function for the random differential reinforcement of low rates schedule. We argue that Beak paves the way for greater understanding of schedules of reinforcement, addressing still open questions about quantitative features of simple schedules. Also, Beak could guide future experiments that use schedules as theoretical and methodological tools.

Varying reinforcer dimensions during differential reinforcement without extinction: A translational model.

Procedural arrangements of differential reinforcement of alternative behavior without extinction often involve presenting the same reinforcers for problem behavior and appropriate behavior, which is typically ineffective at reducing problem behavior and increasing an alternative response. However, manipulating reinforcement dimensions such that the contingencies favor the alternative response may improve treatment outcomes when using differential reinforcement of alternative behavior without extinction by increasing appropriate behavior and reducing problem behavior. We conducted this translational study with 32 college students completing a button-pressing task on a computer program in which they could engage in analogs to problem behavior and appropriate behavior. The effects of manipulating magnitude, immediacy, quality, and a combination of all three dimensions for the alternative response were evaluated. Overall, all dimension manipulations reduced the analog to problem behavior, with the largest reductions observed during the quality probe and the probe with all dimensions combined. These results support the notion that differential reinforcement of alternative behavior without extinction can be an effective form of treatment.

Effect of signaled reinforcement on response variability.

Three experiments examined the effect of signaling reinforcement on rats' lever pressing on contingencies that reinforced variable responding to extend the exploration of signaled reinforcement to a schedule that has previously not been examined in this respect. In Experiment 1, rats responding on a lag-8 variability schedule with signaled reinforcement displayed greater levels of variability (U values) than rats on the same schedule lacking a reinforcement signal. In Experiment 2, rats responding on a differential reinforcement of least frequent responses schedule also displayed greater operant variability with a signal for reinforcement compared with rats without a reinforcement signal. In Experiment 3, a reinforcement signal decreased the variability of a response sequence when there was no variability requirement. These results offer empirical corroboration that operant variability responds to manipulations in the same manner as do other forms of operant response and that a reinforcement signal facilitates the emission of the required operant.

Case study: Modifying repetitive behavior in a polar bear (Ursus maritimus).

Stereotypic pacing in zoo-housed carnivores has been intensively researched for decades, revealing that it is a subtly complex behavior with a highly variable etiology. While pacing can be an indicator of poor welfare, it can also be anticipatory in nature, or even have a completely different motivating operation. In this case study, the pacing of a zoo-housed polar bear, "Tundra," was maintained through inadvertent reinforcement. Baseline data revealed that in 86% of afternoon observations, Tundra paced when the door to shift him off-exhibit was opened. Upon changing the contingencies of reinforcement, there was a change in his behavior; initially with a shift in time, and then a shift in duration. Using a strategy of Differential Reinforcement of an Incompatible behavior, the pacing bout duration significantly decreased from a median of 4 min 13 s to 2 min 26 s. Due to the potential for repetitive walking to negatively influence captive carnivore welfare and the high individual variability of this behavior, investigation into the ontogeny and motivation for these behaviors should continue.

Neonatal exposure to ultrafine iron but not combined iron and sulfur aerosols recapitulates air pollution-induced impulsivity in mice.

Air pollution (AP) is becoming recognized as a major threat to neurological health across the lifespan with increased risk of both neurodevelopmental and neurodegenerative disorders. AP is a complex mixture of gases and particulate matter, with adsorbed contaminants including metals and trace elements, which may differentially contribute to its neurodevelopmental impacts. Iron (Fe) is one of the most abundant metals found in AP, and Fe concentrations may drive some behavioral deficits observed in children. Furthermore, brains of neonate mice exposed to concentrated ambient ultrafine particulate matter (UFP) show significant brain accumulation of Fe and sulfur (S) supporting the hypothesis that AP exposure may lead to brain metal dyshomeostasis. The current study determined the extent to which behavioral effects of UFP, namely memory deficits and impulsive-like behavior, could be recapitulated with exposure to Fe aerosols with or without concomitant SO2. Male and female neonate mice were either exposed to filtered air or spark discharge-generated ultrafine Fe particles with or without SO2 gas (n = 12/exposure/sex). Inhalation exposures occurred from postnatal day (PND) 4-7 and 10-13 for 4 hr/day, mirroring our previous UFP exposures. Mice were aged to adulthood prior to behavioral testing. While Fe or Fe + SO2 exposure did not affect gross locomotor behavior, Fe + SO2-exposed females displayed consistent thigmotaxis during locomotor testing. Neither exposure affected novel object memory. Fe or Fe + SO2 exposure produced differential outcomes on a fixed-interval reinforcement schedule with males showing higher (Fe-only) or lower (Fe + SO2) response rates and postreinforcement pauses (PRP) and females showing higher (Fe-only) PRP. Lastly, Fe-exposed, but not Fe + SO2-exposed, males showed increased impulsive-like behavior in tasks requiring response inhibition with no such effects in female mice. These findings suggest that: 1) exposure to realistic concentrations of Fe aerosols can recapitulate behavioral effects of UFP exposure, 2) the presence of SO2 can modulate behavioral effects of Fe inhalation, and 3) brain metal dyshomeostasis may be an important factor in AP neurotoxicity.

Response-strengthening effects of same- and different-context DRA training: The effects of two disruptors.

Differential reinforcement of alternative behavior (DRA) involves placing problem behavior under extinction and simultaneously reinforcing a desirable behavior. Recent research revealed that, as predicted by Behavioral Momentum Theory, DRA may also increase the persistence of the problem behavior. This research has also shown that a different approach to DRA, in which an alternative behavior is trained in a separate context from the target behavior, produces less persistence than the standard procedure. The research on this phenomenon, so far, assessed persistence using extinction as the disruptor. DRA, however, is often implemented under conditions in which extinction of the problem behavior is not feasible. This study evaluated persistence of problem behavior following same- and separate- context DRA training using an alternative disruptor, an additional source of reinforcement. Following a successful reproduction of a previous study of extinction as a disruptor but with domestic hens, this study produced similar findings using an additional source of reinforcement as the disruptor. These findings add to the evidence that alternative DRA arrangements may avoid the response-strengthening effects found with traditional DRA procedures. The findings also demonstrate that disruptors other than extinction can be used to investigate response persistence following DRA and other procedures.

Nominally acceptable integrity failures negatively affect interventions involving intermittent reinforcement.

The finding that differential reinforcement of alternative behavior (DRA) is efficacious at 80% integrity when continuous reinforcement is programmed for alternative responding may have contributed to a perception that integrity at 80% or above is acceptable. However, research also suggests that other interventions (e.g., noncontingent reinforcement) may not remain effective at 80% integrity. The conditions under which 80% integrity is acceptable for common behavioral interventions remains unclear. Therefore, we conducted two human-operant studies to evaluate effects of 80% integrity for interventions with contingent or noncontingent intermittent reinforcement schedules. During Experiment 1, we compared noncontingent reinforcement (NCR) and DRA when implemented with 80% integrity. During Experiment 2, we compared 2 variations of DRA, which included either a ratio or interval schedule to reinforce alternative behavior. Results replicated previous research showing that DRA with a FR-1 schedule programmed for alternative responding resulted in consistent target response suppression, even when integrity was reduced to 80%. In contrast, neither NCR nor interval-based DRA were consistently effective when implemented at 80% integrity. These results demonstrate that 80% integrity is not a uniformly acceptable minimal level of integrity.

Effects of brief post-sample cues signaling presence or absence of reinforcers in delayed matching-to-sample.

When short-term memory is assessed in the delayed matching-to-sample (DMTS) procedure, performance is better when cues signal larger reinforcer magnitudes or higher reinforcer probabilities for correct responding. Previous studies demonstrating signaled-magnitude or signaled-probability effects presented cues for a prolonged period during the sample stimulus and/or retention interval. The present study asked whether a signaled-probability effect would occur with brief post-sample cues that signaled the presence or absence of reinforcement. Five pigeons responded in a DMTS task in which sample stimuli were sometimes followed by a 0.5-s cue signaling that reinforcers would either be available or not available in the current trial, and the retention interval varied from 0.5 s to 20 s. A reliable signaled-probability effect was found when reinforcers were arranged independently and for all correct responses, whereas a smaller, less systematic effect was found when reinforcers were arranged dependently and probabilistically. These findings highlight the importance of reinforcement contingencies and contingency discriminability in remembering, and add to the evidence showing that cues signaling differential reinforcement in DMTS may affect processes during the retention interval and comparison phase, rather than attention to the sample stimulus.

The mitigating effects of enhanced reinforcer magnitude and quality on treatment degradation.

Differential reinforcement of alternative behavior is a common intervention for problem behavior in persons with neurodevelopmental disorders, but it is susceptible to integrity errors that can degrade treatment effects. Manipulating reinforcement parameters to favor alternative behavior might make it more persistent in the face of integrity errors. We devised an analog of differential reinforcement of alternative behavior to examine if enhanced reinforcer magnitude or quality for the alternative response could protect against treatment degradation. Across 2 experiments, reinforcer magnitude or quality was manipulated to favor the alternative response in 1 condition but kept constant across both alternative and target responses in a second condition. Comparisons of the 2 conditions indicated that higher-magnitude or higher-quality reinforcement for alternative behavior can mitigate against treatment degradation when treatment errors occur and provided support for the utility of considering parameters of reinforcement when developing behavioral interventions for problem behavior.

Resurgence increases with repetition.

Resurgence refers to a behavioral process in which a recent response is extinguished (or reinforcement conditions worsen) and a previously extinguished response recurs. In previous research, resurgence has been reliably produced when the resurgence procedure is repeated. Changes in the degree of increase of the resurging response across iterations of the procedure have been inconsistent, however, with some studies showing increases and some showing no changes or decreases in resurgence magnitude. The present study examined the nature of resurgence across repeated iterations of the conventional resurgence procedure by exposing four pigeons to the resurgence procedure six times in succession. In the first condition of the resurgence procedure, pecks on one key (e.g., the left) were reinforced under a variable-interval (VI) 30-s schedule. In the second condition pecks on that key were extinguished, and pecks on another key (e.g., the right) were reinforced under the same schedule. In the final condition there were no programmed consequences for either response. Resurgence was observed in 21 of 24 opportunities (87.5%). Iteration-over-iteration increases in resurgence were observed in 15 of 20 opportunities (75.0%), and this increase was found to be statistically significant. These findings demonstrate that, under certain conditions, resurgence generally increases in magnitude with repeated exposure to the procedures that generate it.

Effects of the Onset of Differential Reinforcer Quality on Skill Acquisition.

Differential reinforcement of a target response is a necessary component of stimulus control transfer procedures. Recent research has further considered the timing (i.e., onset) of differential reinforcement of unprompted correct responding. To date, the onset of differential reinforcement has been inconsistently controlled in studies comparing skill acquisition programs for individuals with developmental disabilities. The current study serves as a systematic replication of prior comparative research to examine the effects of immediate and delayed differential reinforcement onset on the efficiency of acquisition for three individuals with developmental disabilities. The delayed onset of differential reinforcement required the fewest number of exposures to mastery per target across all comparisons. These findings failed to replicate those of prior research on differential reinforcement onset, possibly due to differences in participant characteristics, target tasks, or other required procedural modifications. Considerations for future research on differential reinforcement procedures in skill acquisition programs are described.

Assessing and Treating Anxiety in Individuals with Autism.

Anxiety is a cluster of responses that can involve both operant and respondent behavior, which can be both public and/or private in nature, and occurs when an upcoming aversive stimulus is signaled. Despite the reported high comorbidity of autism and anxiety, there has been very limited research on how to directly assess and treat anxiety, especially with individuals who have limited communication skills. In Study 1, anxiety was assessed in five individuals with autism, ranging in age from 10 to 19 years old. Anxiety was assessed by measuring behavior during (1) a baseline (with no putative anxiety-provoking stimuli present), (2) signals for an upcoming aversive event, and (3) exposure to that aversive event. Anxiety presented in several different ways, as both conditioned activation and suppression, and both with and without problem behavior during the aversive event. In Study 2, individualized treatments involving differential reinforcement of alternative responses and stimulus fading were used to successfully reduce anxious responding in all four participants who displayed anxiety. These studies demonstrated a potentially useful means of assessing anxiety in individuals with autism which may not only help to measure anxious behavior and identify anxiety-provoking events, but may also lead to effective treatment.