Schedule-Induced and Operant Mechanisms that Influence Response Variability: A Review and Implications for Future Investigations

Advancing and Integrating the Cusp Concept to Understand Behavioral Repertoire Dynamics

The behavioral repertoire grows and develops through a lifetime in a manner intricately dependent on bidirectional connections between its current form and the shaping environment. Behavior analysis has discovered many of the key relationships that occur between repertoire elements that govern this constant metamorphosis, including the behavioral cusp: an event that triggers contact with new behavioral contingencies. The current literature already suggests possible integration of the behavioral cusp and related concepts into a wider understanding of behavioural development and cumulative learning. Here we share an attempted step in that progression: an approach to an in-depth characterization of the features and connections underlying cusp variety. We sketch this approach on the basis of differential involvement of contingency terms; the relevance to the cusp of environmental context, accompanying repertoire, or response properties; the connections of particular cusps to other behavioral principles, processes, or concepts; the involvement of co-evolving social repertoires undergoing mutual influence; and the ability of cusps to direct the repertoire either toward desired contingencies or away from a growth-stifling repertoire. We discuss the implications of the schema for expanded applied considerations, the programming of unique cusps, and the need for incorporating cultural context into the cusp. We hope that this schema could be a starting point, subject to empirical refinement, leading to an expanded understanding of repertoire interconnectivity and ontogenetic evolution.

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.

A review of the behavioral effects of response force: Perspectives on measurement and functions

Response force is a fundamental dimension of behavior. Yet, little is known about its functional significance for learning. The present review examines the behavioral effects of force across several domains. Along the way, advantages of different measurement strategies that have been used to study force are evaluated. The behavioral functions of force are also considered in light of two commonly expressed notions about behavior. First, the Law of Least Effort predicts that animals and humans will act in ways that minimize the costs of behaving. Second, it is widely held that work requirements and effortful responding are aversive. A review of the literature, especially regarding behavioral adaptations to force, is consistent with the Law of Least Effort on many points. Empirical data are less clear on the aversive properties of force requirements. For much of the literature, there is little in coherent findings. Many disagreements and inconsistencies pertain to measurement strategies that fail to record the full range of response variants. Consistent support for aversive functions of force requirements have been obtained only when studied as a negative reinforcer.

A Critical Review of the Support for Variability as an Operant Dimension

There is abundant evidence that behavioral variability is more predominant when reinforcement is contingent on it than when it is not, and the interpretation of direct reinforcement of variability suggested by Page and Neuringer, Journal of Experimental Psychology: Animal Behavior Processes, 11(3), 429-452 (1985) has been widely accepted. Even so, trying to identify the underlying mechanisms in the emergence of stochastic-like variability in a variability contingency is intricate. There are several challenges to characterizing variability as directly reinforced, most notably because reinforcement traditionally has been found to produce repetitive responding, but also because directly reinforced variability does not always relate to independent variables the same way as more commonly studied repetitive responding does. The challenging findings in variability experiments are discussed, along with alternative hypotheses on how variability contingencies may engender the high variability that they undeniably do. We suggest that the typical increase in behavioral variability that is often demonstrated when reinforcement is contingent on it may be better explained in terms of a dynamic interaction of reinforcement and extinction working on several specific responses rather than as directly reinforced.

A Systematic Review of Interventions to Promote Varied Social-Communication Behavior in Individuals With Autism Spectrum Disorder

Individuals with autism spectrum disorder (ASD) may engage in repetitive social-communication behaviors that can limit their skill acquisition, access to reinforcement, and access to less restrictive settings. Basic and applied research indicates that variability, or the extent to which responses are topographically different from one another, is influenced by antecedent and consequence interventions. Our purpose in this study is to systematically review the literature on interventions to increase variable social-communication behaviors in individuals with ASD. We identified 32 studies through a database search and screened them using the What Works Clearinghouse (WWC) Single-Case Design Standards. Eighteen studies containing 55 cases met WWC Design Standards. We coded the descriptive characteristics and strength of evidence based on visual analysis from each of these 18 studies and calculated effect sizes using Tau-U. Our results indicate that most cases (65%) provide strong evidence of a functional relation between the interventions and varied social-communication behaviors, and the median Tau-U was .82. We discuss the implications of our results for practice and for future research on interventions designed to increase variability with this population.

Effects of a Lag Schedule with Progressive Time Delay on Sign Mand Variability in a Boy with Autism

For some children with autism, mand training can produce highly repetitive manding unless the environment is arranged in a manner that promotes mand variability. Prior research demonstrated that mand training using a lag schedule and progressive time delay increased variability in vocal manding in children with autism. Whether lag schedules have similar effects on sign mand topographies is unknown. The current study evaluated the effects of mand training with a Lag 1 schedule of reinforcement and progressive time delay (TD) on topographical variability and the development of a sign mand response class hierarchy in a boy with autism. The results suggest independent use of all sign mand topographies occurred, a mand response class hierarchy was developed, and topographically variant sign manding increased under the Lag 1 + TD schedule compared to a Lag 0 schedule of reinforcement. Implications for practitioners, limitations, and directions for future research are discussed.

An evaluation of lag schedules and prompting methods to increase variability of naming category items in children with autism spectrum disorder

A lag schedule of reinforcement is one way to increase response variability; however, previous research has been mixed with regard to the necessary parameters to increase variability. For some individuals, low schedule requirements (e.g., Lag 1) are sufficient to increase variability. For other individuals, higher lag schedules (e.g., Lag 3) or a lag schedule in combination with prompting is needed to increase variability. We evaluated the efficiency of different within-session progressive lag schedules to increase response variability with 2 children with autism. Results showed that increasing the lag criterion across sessions increased variability to levels similar to beginning with a high lag schedule for one participant. When lag schedules did not increase variability for the second participant, we compared a variety of prompting procedures. Results of the prompting evaluation showed that a tact-priming procedure was effective to increase varied responding.

An analysis of procedures that affect response variability

Response variability is sensitive to antecedent and consequent manipulations. Researchers have investigated inducement, direct production through reinforcement, and stimulus control of response variability. Recently, researchers have shown that lag reinforcement schedules reliably increase variability but may also produce higher-order stereotypy. There has been limited investigation of appropriate variability levels and alternation between repetition and variation. In a three-part study, we evaluated levels of variability across a group of children, the effects of various procedures on producing response variability and novelty, and the use of schedule-correlated stimuli for producing rapid alternation between repetition and variation. In Study 1, there was a nearly bimodal distribution of children emitting either low or high variability. In Study 2, for most children, fixed lag 4 and variable lag 4 schedules produced the highest levels of variability and novelty. In Study 3, responding was brought under control of schedule-correlated stimuli, allowing for rapid alternation between repetition and variation.

Effects of Simultaneous Script Training on Use of Varied Mand Frames by Preschoolers with Autism

Young children with autism may fail to mand using a range of frames (e.g., "I want," "May I have," "Please give me"). We examined the effects of simultaneous script training and script fading on acquisition and maintenance of varied mand frames with six preschool children with autism. For participants who did not demonstrate increased mand variability under fixed-ratio (FR) 1 conditions, we assessed the effects of post script-training extinction on response variability. Following training of up to four different mand frames, three of six participants emitted more varied mands under FR1 conditions relative to baseline. Posttraining extinction resulted in increased mand variability for two of the three remaining participants. Results are discussed in terms of considerations for both establishing and ensuring the persistence of varied verbal behavior among children with autism.

Promoting Accurate Variability of Social Skills in Children With Autism Spectrum Disorder

Restricted and repetitive behavior is a central feature of autism spectrum disorder (ASD), with such behaviors often resulting in lack of reinforcement in social contexts. The present study investigated training multiple exemplars of target behaviors and the utilization of lag schedules of reinforcement in the context of social skills training to promote appropriate and varied social behavior in children with ASD. Five participants with ASD between the ages of 7 and 9 attended a twice-weekly social skills group for 8 weeks. A multiple probe design across skills was utilized to assess intervention effects. During baseline, participants demonstrated low levels of skill accuracy and low appropriate variability in responding. During continuous reinforcement with one trained exemplar, skill accuracy increased while appropriate variability remained low. Training of three exemplars of target skills resulted in minimal improvements in appropriate variability. Introduction of a Lag 2 schedule with three trained exemplars was generally associated with increased appropriate variability. Further appropriate variability was observed during Lag 4 with three trained exemplars. Limitations and implications are discussed.

Applicability to foraging simulation of a reinforcement schedule controlling the response energy of pigeons

In optimal foraging theory (OFT), energy expenditure is an important variable for predicting foraging behavior. However, early studies, including operant simulations of foraging, did not measure energy expenditure. In the present study, an adjusting energy (AE) schedule was developed to control energy expenditure. Interresponse energy (IRE), a measure of the energy expenditure during a response, was calculated by dividing the square of the elapsed time between two consecutive responses by the square of the straight-line distance between the locations of the same two responses. An adjusting procedure was employed to estimate the indifference point between the requirements of the AE schedule and a fixed ratio (FR) schedule, which has been used in many operant simulations. In the adjusting procedure, pigeons adjusted the requirement of the AE schedule to that of the FR schedule. The results showed a systematic relationship between the requirements of the AE and FR schedules. Moreover, the total IRE per reinforcement systematically increased with the AE requirement. Thus, the present study demonstrates the utility of the AE schedule as a procedure for testing the validity of OFT.

Increasing response variability of mand frames with script training and extinction

We examined the effects of script training and extinction on response variability of mand frames used by children with autism. Results demonstrated that extinction following script training was effective for increasing variability for 2 of the 3 participants.

Reinforcing saccadic amplitude variability

Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we reinforced the least frequent saccadic amplitudes to increase variability, and then reinforced the central part of the amplitude distributions to reduce variability. The target was placed at a constant distance from the fovea after the saccade to maintain the postsaccadic visual signal constant and an auditory reinforcement was delivered depending on saccadic amplitude. The second experiment tested the effects of the contingency. We reinforced high levels of variability in 4 participants, whereas 4 other participants were assigned to a yoked control group. On average, saccadic amplitude standard deviations were doubled while the medians remained mostly unchanged in the experimental participants in both experiments, and variability returned to baseline level when low variability was reinforced. In the control group no consistent changes in amplitude distributions were observed. These results, showing that variability can be reinforced, challenge the idea of a stochastic neural noise. We instead propose that selection processes constrain saccadic amplitude distributions.

Molar functional relations and clinical behavior analysis: implications for assessment and treatment

The experimental analysis of behavior has identified several molar functional relations that are highly relevant to clinical behavior analysis. These include matching, discounting, momentum, and variability. Matching provides a broader analysis of how multiple sources of reinforcement influence how individuals choose to allocate their time and offers an empirical rationale for reducing problem behavior by increasing adaptive behavior. Discounting highlights the functional relations that affect self-control. Momentum specifies the variables responsible for persistence in challenging situations. Variability characterizes a functional dimension of behavior that is essential for learning and problem solving. These concepts have important implications for clinical practice and research. A selective review of these concepts is presented, and their implications for assessment and treatment are discussed with two goals: to inform basic scientists about the relevance of their work and to invite clinical behavior analysts to broaden the conceptual basis for their work.