Richer Schedule Research Articles

Adaptive learning and forgetting in an unconventional experimental routine.

Forgetting is often thought of as the inability to remember, but remembering and forgetting allow behavior to adapt to a changing environment in distinct and separable ways. Learning and forgetting were assessed concurrently in two pigeon experiments that involved the same unconventional routine where the schedule of reinforcement changed every session. Sessions were run back-to-back with a 23-h mid-session break such that in a single visit to the testing chamber, a pigeon completed the second half of one session and the first half of the next. The beginning of a new session was either signaled or unsignaled. Experiment 1 involved concurrent variable-interval variable-interval schedules with four possible reinforcer ratios. Response allocation was sensitive to the richer schedule and was retained through the mid-session break. Experiment 2 involved peak interval schedules of varying durations. Temporal discrimination was rapidly acquired before and after the mid-session break, but not retained. Signaling the session change decreased control by past contingencies in both experiments, demonstrating that learning and forgetting can be investigated separately. These results suggest that the temporal structure of training, such as multiple short daily sessions instead of one long session, can meaningfully impact measurement of animals' capacity to forget and remember.

Stimulus Fading and Response Elaboration in Differential Reinforcement for Alternative Behavior.

A hallmark of applied behavior analysis is the development of function-based interventions for problem behavior. A widely recommended function-based intervention is differential reinforcement of alternative behavior (DRA), in which reinforcement is contingent upon socially acceptable alternatives to problem behavior (e.g., teaching communication skills). Typically, DRA is introduced under rich schedules of reinforcement. Although effective for initiating behavior change, rich schedules are often impractical in the natural setting. In this study, we evaluated the extent to which a stimulus fading program could be employed to elaborate alternative behavior (mands) in two individuals diagnosed with an Autism Spectrum Disorder. For both participants, problem behavior was reduced substantially upon implementation of the DRA procedure. Further, problem behavior rates remained low and mand rates decreased to more practical levels as the DRA behavioral requirements increased during the fading program. The fading approach demonstrated in this paper may be a useful component of intervention packages for clinicians.

Concurrent Token Production in Rats

The current study assessed whether the generalized matching law would provide an accurate description of behavior maintained by token reinforcement. A dependent-concurrent random interval 15 s schedule of token production maintained lever pressing in rats. Following delivery, each token could be immediately exchanged for sweetened condensed milk. In Experiment 1, the token ratio was either 1:3 or 1:9, depending upon condition, and the location of the rich schedule varied randomly across daily sessions. In Experiment 2, the token ratio varied randomly within each session (1:9, 1:6, 1:3, 1:1, 3:1, 6:1, and 9:1). Overall, the generalized matching law provided a good description of the data, revealing a high degree of undermatching. In Experiment 2, two of three rats tended to return to the just-productive lever following token delivery. The third subject showed this pattern only following left-token deliveries. Overall, the effects of token reinforcers on choice were similar to those observed with other reinforcers.

Population pharmacokinetics and pharmacodynamic evaluation of intravenous and enteral moxifloxacin in surgical intensive care unit patients

To describe the plasma concentration-time profile of moxifloxacin after intravenous and enteral administration in intensive care unit (ICU) patients and to provide a pharmacodynamic (PD) evaluation with regard to pneumonia. Twenty-five adult patients from a cardiothoracic/mixed surgical ICU were enrolled. Moxifloxacin was given as a standard dose (400 mg once daily). Therapy was successfully switched to enteral administration on day 5 in 16 patients. A rich data sampling schedule was performed after intravenous (day 4) and enteral (day 8) administration. Moxifloxacin concentrations were analysed by HPLC. A population pharmacokinetic (PK) model was developed using NONMEM VII. Simulated concentration-time profiles were evaluated for their probability of attaining PK/PD target values relevant for community-acquired pneumonia (CAP) and hospital-acquired pneumonia (HAP). A linear-elimination two-compartment model described the data adequately. Parameter estimates (coefficient of variation of inter-individual variability) were: absorption rate constant, 1.09/h (135%); enteral bioavailability, 76% (20.0%); central volume of distribution, 55.6 L; peripheral volume of distribution, 59.6 L (15.3%); inter-compartmental clearance, 47.7 L/h; and clearance, 11.3 L/h (23.7%). Both intravenously and enterally administered standard-dose moxifloxacin reliably attained the PK/PD target values for pathogens with MICs ≤ 0.25 mg/L for CAP and ≤ 0.125 mg/L for HAP. Drug exposure to moxifloxacin in ICU patients was more variable than in healthy volunteers. The standard dosing provides sufficient drug exposure for treatment of CAP but for HAP it does so only when a highly susceptible pathogen is present. Intravenous/enteral sequential therapy may be considered for cautiously selected cases in ICU patients.

Prompt Density, Rate of Reinforcement, and the Persistence of Manding

Previous research has documented the effects of prompting mands at a relatively high rate (i.e., rich schedule) or low rate (i.e., lean schedule). These previous studies have not addressed the possibility of prompt dependency as an explanation for these results. Furthermore, the implications of a collateral effect of prompt density, increased response-reinforcer pairings, have not been investigated. The current studies sought to address these two questions. During Experiment 1, the effect of prompt density (i.e., high and low prompt rate) on manding was evaluated. The inclusion of a control condition (i.e., prompts in the absence of the relevant establishing operation and reinforcement) isolated the effect of prompts on manding. During Experiment 2, a collateral effect of relatively high prompt density, increased reinforcer rate, on response persistence was evaluated. Results showed that manding rates varied with prompt rate and did not appear to be prompt dependent. Finally, mands persisted longer following a relatively rich prompt schedule than a relatively lean prompt schedule.

CONTEXTUAL INFLUENCES ON RESISTANCE TO DISRUPTION IN CHILDREN WITH INTELLECTUAL DISABILITIES

Training context can influence resistance to disruption under differing reinforcement schedules. With nonhumans, when relatively lean and rich reinforcement schedules are experienced in the context of a multiple schedule, greater resistance is found in the rich than the lean component, as described by behavioral momentum theory. By contrast, when the schedules are experienced in separated blocks of sessions (i.e., as single schedules), resistance is not consistently greater in either component. In the current study, two groups of 6 children with intellectual disabilities responded to stimuli presented in relatively lean or rich components. For both, reinforcers were delivered according to the same variable-interval reinforcement schedule; additionally, the rich component included the delivery of response-independent reinforcers. The Within group was trained on a multiple schedule in which lean and rich components alternated regularly within sessions; the Blocked group was trained on two single schedules in which sessions with either the lean or rich schedule were conducted in successive blocks. Disruption tests presented a concurrently available alternative stimulus disrupter signaling the availability of tangible reinforcers. All 6 Within participants showed greater resistance to disruption in the rich component, consistent with behavioral momentum theory. By contrast, there was no consistent or significant difference in resistance for Blocked participants. This finding is potentially relevant to the development of interventions in applied settings, where such interventions often approximate single schedules and include response-independent reinforcers.

A Switch in the Neuromodulatory Effects of Dopamine in the Oval Bed Nucleus of the Stria Terminalis Associated with Cocaine Self-Administration in Rats

Chronic exposure to drugs of abuse alters brain reward circuits and produces functional changes in the dopamine (DA) system. However, it is not known whether these changes are directly related to drug-driven behaviors or whether they simply are adaptive responses to long-term drug exposure. Here, we combined the rat model of cocaine self-administration with brain slice electrophysiology to identify drug-use related alterations in the neuromodulatory effects of DA in the oval bed nucleus of the stria terminalis (ovBST), a robust DA terminal field. Long-Evans rats self-administered cocaine intravenously (0.75 mg/kg/injection) for an average of 15 d, on reward-lean or -rich schedules of reinforcement. Brain slice recordings conducted 20 h after the last self-administration session revealed a reversal of the neuromodulatory effect of DA on GABA(A)-IPSCs. Specifically, the effect of DA switched from a D2-mediated decrease in drug-naive rats to a D1-receptor-mediated increase in GABA(A)-IPSC in cocaine self-administering rats. Furthermore, the switch in DA modulation of GABA(A)-IPSC remained after a 30 d withdrawal period. In contrast, this switch was not observed after the acquisition phase of cocaine self-administration, when rats received cocaine passively, or in rats maintaining sucrose self-administration. Therefore, our study reveals a reversal in the effects of DA on inhibitory transmission, from reduction to enhancement, in the ovBST of cocaine self-administering rats. This change was unique to voluntary intake of cocaine and maintained after a withdrawal period, suggesting a mechanism underlying the maintenance of cocaine self-administration and perhaps craving during drug-free periods.

Using Descriptive Assessment in the Treatment of Bite Acceptance and Food Refusal

The feeding behaviors of two children who maintained failure to thrive diagnoses and displayed food refusal are assessed in their homes. Descriptive assessments are used to identify schedules of consequence provided by each child's care providers for bite acceptance and food refusal behaviors. Assessments reveal rich schedules of praise and access to social interaction and preferred activities for bite acceptance and escape for food refusal. These schedule arrangements result in hypotheses that modifications to the schedule of praise and access to social interaction and preferred activities for bite acceptance would result in little to no effect and that modifications to the schedule of escape for food refusal would be necessary for treatment success. Successful interventions are subsequently implemented by manipulating the existing schedules of escape for food refusal by each child's care providers. Implications for the use of descriptive assessments for feeding problems are discussed.

Within-session patterns in variable-interval schedule performance: Variation with deprivation level

Previous research has shown that patterns in operant responding may change within the course of individual experimental sessions. The proper interpretation of such changes is controversial. At least one source of this controversy may lie in unstated experimental practices across laboratories, as published reports often have failed to detail important particulars of deprivation operations. The present study was aimed at gathering descriptive data on the contribution of deprivation operations to the observation of within-session changes. In two experiments, four food deprived pigeons were exposed to a multiple variable-interval 30-s variable-interval 30-s schedule of grain presentation, wherein each grain presentation was kept constant at 5s. In Condition I, a session-entry criterion was in place that permitted the pigeon access to the daily session only if its body weight fell within controlled limits. Within-session rates of responding were generally stable. In Condition II, the entry criterion was removed and experimental sessions were conducted 6 days per week. The effect of removing the session-entry criterion was to increase body weight for all birds and decrease food intake across conditions. With no session entry criterion, robust within-session changes were observed for three of the four pigeons. The results suggest that rich schedules of reinforcement often used in the analysis of within-session changes can produce substantial reductions in deprivation levels that require up to several days to reverse. Future experiments in this area should take precautions to insure that deprivation is tightly controlled and report such measures to eliminate potential errors in replication.

The Use of Descriptive Analysis to Identify and Manipulate Schedules of Reinforcement in the Treatment of Food Refusal

The feeding behaviors of a child diagnosed with failure to thrive were assessed using descriptive analysis methodology to identify the schedules of reinforcement provided by the child's parents. This analysis revealed that the child's appropriate feeding behaviors (i.e., bite acceptance, self-feeding) were on a lean schedule of positive reinforcement and that the child's refusal behaviors (e.g., non-acceptance, expulsion) were on a rich schedule of negative reinforcement. A treatment package consisting of differential positive reinforcement for bite acceptance with and without escape extinction was evaluated by manipulating the schedules of reinforcement that were identified to be used by the child's parents. The results showed a reduction of the child's inappropriate mealtime behaviors and increases in the child's acceptance of offered food items. The results also suggested that the differential reinforcement component appeared to be most responsible for ongoing effectiveness of the treatment. These results are discussed in terms of treating the food refusal behavior of children diagnosed with failure to thrive as a preventive measure for later development of developmental disabilities.

Understanding intra-response class covariation from the matching theory perspective.

Abstract The purpose of this study was to utilize the matching theory to understand intra-response class covariation as a result of extinction for selected members of the response class versus functional communication training. The participant was a 9-year old girl with a severe disability and problem behaviors. Experimental procedures included functional analysis, extinction, and functional communication training. Results showed that in accordance with the matching theory, responses (problem or adaptive) that were continuously reinforced occurred at a higher rate when compared to responses on extinction. In addition, extinction for some problem responses increased the rate of non-targeted problem responses; however, concurrent reinforcement of a newly learned functionally equivalent communication response increased the rate of this behavior and decreased all problem behaviors. Keywords: Matching theory, response class, covariation, extinction, functional communication training, developmental disabilities, problem behavior. *********** Researchers and practitioners continue to be fascinated with understanding and analyzing operant behavior patterns to facilitate the development of enduring behavior support strategies. Toward that goal, the matching theory continues to serve as a foundation for furthering our understanding of the causes of socially mediated behavior specifically for individuals with disabilities and/or behavior disorders. Herrnstein (1970) describes the matching law as a mathematical means for elucidating how behavior responds to concurrent schedules of reinforcement. Stated simply, responses that are consequated with a higher number of reinforcers occur at higher rates than responses that are reinforced at lower (or zero) rates. Both rational and irrational behavior has been explained using the matching theory (Borrero & Vollmer, 2002; Bulow & Meller, 1998; Shriver & Kramer, 1997; Skinner & Robinson, 1996). The basic assumption is that response allocation of operant behavior is a matter of choice. A choice of any topography over the others at a given point in time is possible only when multiple responses are involved, all of which produce the same functional effect. The literature has described this pattern as a functional response class (Lalli, Mace, Wohn, & Livezy, 1995; Shukla & Albin, 1996; Shukla-Mehta & Albin, 2003; Sprague & Horner, 1992). The concept of response classes is not novel. Still, researchers and practitioners continue to focus attention on understanding what governs choice or the allocation of specific topographies from a class of responses. Such interest has been generated due to observed covariation as a function of concurrently varying rates of reinforcement for the different topographies within a response class (Magee & Ellis, 2000; Parrish, Cataldo, Kolko, Neef, & Egel, 1986). In addition, there has been an observed philosophical shift in the field from the use of decelerative techniques alone in favor of strategies that also lead to increases in adaptive behavior (Carr, Coriaty, & Dozier, 2000; Carr & Durand, 1985; Day, Horner, & O'Neill, 1994; Dunlap, et al, 1995; Horner & Carr, 1997; Horner, Sprague, O'Brien, & Heathfield, 1990; Sugai et al., 2000). With the advent of hypotheses-based interventions and the focus on identification of multiple topographies within a functional response class, application of the matching theory to understand behavioral allocation has gained momentum. If some topographies within a response class are consequated with a richer schedule of reinforcement (positive or negative), these will occur at higher rates. Our clinical experiences show that more severe topographies of problem behaviors usually lead to a functional reinforcer, example, escape from non-preferred tasks, attention form others, access to tangible objects, and/or sensory reinforcement. …

Carryover effects of free reinforcement on children's work completion.

Patterns of behavior that persist during transition to a new set of contingencies are referred to as reinforcement history or carryover effects. The authors examined the carryover effects of a fixed-time (FT) schedule of free reinforcement on children's work completion and accuracy. Two female students with learning disabilities participated. During an initial concurrent-choice condition, both children completed more difficult problems reinforced on a richer schedule than easy problems reinforced on a leaner schedule. Exposure to an FT schedule was alternated with subsequent choice conditions in an ABABA design to examine potential carryover effects. During FT conditions, the children completed both types of problems with more errors. During subsequent choice conditions, errors were high initially but decreased, and both children completed easy problems for the first few sessions despite their leaner reinforcement schedule. The potential for detrimental effects of free reinforcement on children's work completion is discussed.

The Effect of Response-Dependent Tones on the Acquisition of Concurrent Behavior in Rats

Four experiments examined the effect of a loud auditory stimulus on rats' acquisition of responding on a concurrent reinforcement schedule. A between-groups procedure was adopted to explore the conditions under which a response-contingent tone would serve as a punishing stimulus. It was found that a brief tone (0.5 s), superimposed on a lean schedule (Experiment 1), produced the greatest response suppression. In contrast, a longer tone (1.5 s) on a rich schedule was ineffective in suppressing responding (Experiment 4). Alternative combinations of the parameters (Experiments 2 and 3) produced intermediate response suppression. When response suppression was noted, a preference shift toward the alternative with richer reinforcement schedule was observed when the tone schedule was added. These experiments replicate the previous demonstrations of the suppressive effects of a tone, but extend the effects to acquisition rather than stable state behavior.

ATTENTION AS AN ESTABLISHING OPERATION AND AS REINFORCEMENT DURING FUNCTIONAL ANALYSES

Results of functional analyses for 36 individuals whose self‐injurious behavior (SIB) was maintained by attention indicated that SIB was highest during a condition in which the individual was deprived of attention (establishing operation) except as a consequence (reinforcer). Deprivation in the absence of reinforcement produced marginal increases in SIB in 5 individuals, and a relatively rich schedule of noncontingent attention produced the lowest levels of SIB. These results suggest that clearer functional analysis outcomes are likely to be obtained when test conditions contain both an establishing operation to evoke behavior as well as a reinforcement contingency to maintain it.

Value transfer in concurrent-schedule discriminations by pigeons

When pigeons are trained on a discrete-trial simultaneous discrimination, some of the value associated with the positive stimulus appears to transfer to the negative stimulus (Zentall & Sherburne, 1994). Pigeons preferred a negative stimulus that had been discriminated from an always-positive stimulus (S+) over a negative stimulus that had been discriminated from a sometimes-positive stimulus (S±). A very different finding (suggestive of transitivity of preference or contrast) was reported by Belke (1992). On concurrent probe tests of stimuli associated with equal variable interval (VI) schedules but originally trained in alternative concurrent pairs (one with a richer schedule, the other with a poorer schedule—VI 20 sec vs. VI 40 sec and VI 40 sec vs. VI 80 sec), the stimulus originally paired with the poorer schedule was preferred. But Belke’s results may have been obtained because the pigeons had been trained to peck the VI 40 sec paired with the poorer schedule and they had been trained not to peck the VI 40 sec paired with the richer schedule. In the present experiment, we avoided this bias by training pigeons on two concurrent schedules in which the tested stimuli both had been associated with the poorer schedule of the pair [A(VI 20 sec) vs. B(VI 80 sec) and C(VI 40 sec) vs. D(VI 80 sec)]. Evidence for value transfer was demonstrated when on probe trials pigeons preferred B over D.

Dynamics of time matching: Arousal makes better seem worse

Matching of time allocation across alternatives in proportion to relative reinforcement rates is a ubiquitous finding in the animal-learning literature on choice. The dynamics of the underlying mechanism, however, remain poorly understood. A recent finding by Belke (1992) profoundly challenges scalar expectancy theory (SET; Gibbon et al., 1988) and other accounts of matching in concurrent variable interval (VI) schedules. He studied concurrent probe tests of stimuli associated with equal VIs but trained in alternative concurrent pairs. In training, one was preferred and the other not. Unreinforced probes revealed a strong preference for the alternative preferred in training. An experiment is reported replicating this result and showing that it is not due to generalization of preference levels from training. When the probe is between the two preferred training stimuli, the richer schedule is unpreferred. A SET account of these results is presented which implicates two processes in time allocation: (1) the choice between alternatives based on memory for delays to reinforcement, and (2) the times at which such choices are made. The former process is sensitive to reinforcement scheduling; the latter is sensitive to arousal levels induced by overall reinforcement rates in training.

Impulsivity in students with serious emotional disturbance: the interactive effects of reinforcer rate, delay, and quality.

We conducted two studies extending basic matching research on self-control and impulsivity to the investigation of choices of students diagnosed as seriously emotionally disturbed. In Study 1 we examined the interaction between unequal rates of reinforcement and equal versus unequal delays to reinforcer access on performance of concurrently available sets of math problems. The results of a reversal design showed that when delays to reinforcer access were the same for both response alternatives, the time allocated to each was approximately proportional to obtained reinforcement. When the delays to reinforcer access differed between the response alternatives, there was a bias toward the response alternative and schedule with the lower delays, suggesting impulsivity (i.e., immediate reinforcer access overrode the effects of rate of reinforcement). In Study 2 we examined the interactive effects of reinforcer rate, quality, and delay. Conditions involving delayed access to the high-quality reinforcers on the rich schedule (with immediate access to low-quality reinforcers earned on the lean schedule) were alternated with immediate access to low-quality reinforcers on the rich schedule (with delayed access to high-quality reinforcers on the lean schedule) using a reversal design. With 1 student, reinforcer quality overrode the effects of both reinforcer rate and delay to reinforcer access. The other student tended to respond exclusively to the alternative associated with immediate access to reinforcers. The studies demonstrate a methodology based on matching theory for determining influential dimensions of reinforcers governing individuals' choices.

Pavlovian contingencies and anticipatory contrast

Pigeons were trained on a four-component multiple schedule in which two target components with identical reinforcement schedules were followed by other components with either higher or lower reinforcement rates. The Pavlovian signal properties of the target-component stimuli were varied by changes in their duration relative to the following components, and by whether the two following components were cued by the same or different stimuli, When different stimuli occurred in the following components, response rates were higher in the target component preceding the following component with the lower reinforcement rate, and these contrast effects were larger with shorter relative durations. But with nondifferential stimuli in the following components, contrast consistently occurred only with the longer durations of the target components. Moreover, several subjects with the shorter duration target stimuli had higher response rates in the target followed by the richer schedule—that is, Pavlovian conditioning occurred to the target stimuli. This interaction suggests that the processes underlying anticipatory contrast and Pavlovian conditioning are in opposition, and that the Pavlovian effect can dominate ifthe signaling properties of the target components are sufficiently enhanced.

DECISION RULES AND SIGNAL DETECT ABILITY IN A REINFORCEMENT‐DENSITY DISCRIMINATION

Two probabilistic schedules of reinforcement, one richer in reinforcement, the other leaner, were overlapping stimuli to be discriminated in a choice situation. One of two schedules was in effect for 12 seconds. Then, during a 6-second choice period, the first left-key peck was reinforced if the richer schedule had been in effect, and the first right-key peck was reinforced if the leaner schedule had been in effect. The two schedule stimuli may be viewed as two binomial distributions of the number of reinforcement opportunities. Each schedule yielded different frequencies of 16 substimuli. Each substimulus had a particular type of outcome pattern for the 12 seconds during which a schedule was in effect, and consisted of four consecutive light-cued 3-second T-cycles, each having 0 or 1 reinforced center-key pecks. Substimuli therefore contained 0 to 4 reinforcers. On any 3-second cycle, the first center-key peck darkened that key and was reinforced with probability .75 or .25 in the richer or leaner schedules, respectively. In terms of the theory of signal detection, detectability neared the maximum possible d' for all four pigeons. Left-key peck probability increased when number of reinforcers in a substimulus increased, when these occurred closer to choice, or when pellets were larger for correct left-key pecks than for correct right-key pecks. Averaged over different temporal patterns of reinforcement in a substimulus, substimuli with the same number of reinforcers produced choice probabilities that matched relative expected payoff rather than maximized one alternative.