Assessment of impulsivity and the development of self-control in students with attention deficit hyperactivity disorder.

We examined a combined approach of manipulating reinforcer dimensions and delay fading to promote the development of self‐control with 3 students diagnosed with attention deficit hyperactivity disorder. First, we administered a brief computer‐based assessment to determine the relative influence of reinforcer rate (R), reinforcer quality (Q), reinforcer immediacy (I), and effort (E) on the students' choices between concurrently presented math problems. During each session, one of these dimensions was placed in direct competition with another dimension (e.g., RvI involving math problem alternatives associated with high‐rate delayed reinforcement vs. low‐rate immediate reinforcement), with all possible pairs of dimensions presented across the six assessment conditions (RvQ, RvI, RvE, QvI, QvE, IvE). The assessment revealed that the choices of all 3 students were most influenced by immediacy of reinforcement, reflecting impulsivity. We then implemented a self‐control training procedure in which reinforcer immediacy competed with another influential dimension (RvI or QvI), and the delay associated with the higher rate or quality reinforcer alternative was progressively increased. The students allocated the majority of their time to the math problem alternatives yielding more frequent (high‐rate) or preferred (high‐quality) reinforcement despite delays of up to 24 hr. Subsequent readministration of portions of the assessment showed that self‐control transferred across untrained dimensions of reinforcement.     

A COMPARISON OF THE EFFECTS OF BRIEF RULES, A TIMER, AND PREFERRED TOYS ON SELF-CONTROL

Some children make impulsive choices (i.e., choose a small but immediate reinforcer over a large but delayed reinforcer). Previous research has shown that delay fading, providing an alternative activity during the delay, teaching participants to repeat a rule during the delay, combining delay fading with an alternative activity, and combining delay fading with a countdown timer are effective for increasing self‐control (i.e., choosing the large but delayed reinforcer over the small but immediate reinforcer). The purpose of the current study was to compare the effects of various interventions in the absence of delay fading (i.e., providing brief rules, providing a countdown timer during the delay, or providing preferred toys during the delay) on self‐control. Results suggested that providing brief rules or a countdown timer during the delay was ineffective for enhancing self‐control. However, providing preferred toys during the delay effectively enhanced self‐control.     

Self-control in children with autism: response allocation during delays to reinforcement.

This study examined the use of a progressive‐delay schedule of reinforcement to increase self‐control and decrease disruptive behavior in children with autism. When initially given the choice between an immediate smaller reinforcer and a larger delayed reinforcer, all participants chose the smaller reinforcer. When access to the larger reinforcer required either no activity or engaging in a concurrent task during the delay, all participants demonstrated both self‐control and preference for a response requirement. Disruptive behavior decreased during delays that required a concurrent task compared to sessions without an activity requirement.     

Self-control and choice in humans: Effects of video game playing as a positive reinforcer

Participants chose between reinforcement schedules differing in delay of reinforcement (interval between a choice response and onset of a video game) and/or amount of reinforcement (duration of access to the game). Experiment 1 showed that immediate reinforcement was preferred to delayed reinforcement with amount of reinforcement held constant, and a large reinforcer was preferred to a small reinforcer when both were obtainable immediately. Imposing a delay before the large reinforcer produced a preference for the immediate, small reinforcer in 40% of participants. This suggested a limited degree of “impulsivity.” In Experiment 2, unequal delays were extended by equal intervals, the amounts being kept equal. Preference for the shorter delay decreased, an effect that presumably makes possible the “preference reversal” phenomenon in studies of self-control. Overall, the results demonstrate that video game playing can produce useful, systematic data when used as a positive reinforcer for choice behavior in humans.     

Negative reinforcement and choice in humans

Participants chose between reinforcement schedules differing in delay and/or duration of noise offset. In Experiment 1 it was found that (1) immediate reinforcement was preferred to delayed reinforcement when amounts (durations) of reinforcement were equal; (2) a relatively large reinforcer was preferred to a smaller one when both reinforcers were obtained immediately; and (3) preference for an immediate, small reinforcer versus a delayed, large reinforcer increased as the delay preceding the large reinforcer increased, a sign of “impulsivity”. In Experiment 2, the schedules differed in amount or delay and equal intervals were added either to the constant parameter or the varied parameter. A shift from virtually exclusive preference to indifference occurred in the latter case but not the former, a result supporting a model of self-control that assumes that the value of a schedule depends on the ratio of amount and delay, and that choice between schedules depends on the ratio of these values.     

Self‐control as generalized operant behavior by adults with autism spectrum disorder

The present investigation attempted to teach self‐control to 3 adults who had been diagnosed with autism spectrum disorder. Using a self‐control training procedure that coupled a gradual fading of delay to access a large delayed reinforcer with a concurrent work requirement, each participant was exposed to conditions in which baseline levels of choices for large delayed reinforcers and task engagement increased 10‐fold. Furthermore, generalization effects were partially demonstrated in a novel context.     

PREFERENCE FOR A STIMULUS THAT FOLLOWS A RELATIVELY AVERSIVE EVENT: CONTRAST OR DELAY REDUCTION?

Several types of contrast effects have been identified including incentive contrast, anticipatory contrast, and behavioral contrast. Clement, Feltus, Kaiser, and Zentall (2000) proposed a type of contrast that appears to be different from these others and called it within-trial contrast. In this form of contrast the relative value of a reinforcer depends on the events that occur immediately prior to the reinforcer. Reinforcers that follow relatively aversive events are preferred over those that follow less aversive events. In many cases the delay reduction hypothesis proposed by Fantino (1969) also can account for such effects. The current experiments provide a direct test of the delay reduction and contrast hypotheses by manipulating the schedule of reinforcement while holding trial duration constant. In Experiment 1, preference for fixed-interval (FI) versus differential-reinforcement-of-other-behavior (DRO) schedules of reinforcement was assessed. Some pigeons preferred one schedule over the other while others demonstrated a position (side) preference. Thus, no systematic preference was found. In Experiment 2, a simultaneous color discrimination followed the FI or DRO schedule, and following training, preference was assessed by presenting the two positive stimuli simultaneously. Consistent with the contrast hypothesis, pigeons showed a significant preference for the positive stimulus that in training had followed their less preferred schedule.     

EFFECTS OF A SIGNALED DELAY TO REINFORCEMENT IN THE PREVIOUS AND UPCOMING RATIOS ON BETWEEN-RATIO PAUSING IN FIXED-RATIO SCHEDULES

Domestic hens responded under multiple fixed‐ratio fixed‐ratio schedules with equal fixed ratios. One component provided immediate reinforcement and the other provided reinforcement after a delay, signaled by the offset of the key light. The components were presented quasirandomly so that all four possible transitions occurred in each session. The delay was varied over 0, 4, 8, 16, and 32 s with fixed‐ratio 5 schedules, and over 0, 8 and 32 s with fixed‐ratio 1, 15 and 40 schedules. Main effects of fixed‐ratio value and delay duration were detected on between‐ratio pauses. Pauses were longer when the multiple‐schedule stimulus correlated with a delayed‐reinforcer component was presented, with the longest pauses occurring at the transition from a component with an immediate reinforcer to one with a delayed reinforcer. Pause durations were shortest during immediate components. Overall, both the presence or absence of a delay in the upcoming component, and the presence or absence of a delay in the preceding component affected pause length, but the upcoming delay had the larger effect. Thus changes in delay had similar effects to past reports of the effects of changes in response force, response requirement, and reinforcer magnitude in multiple fixed‐ratio fixed‐ratio schedules.     

Evaluation and treatment of covert stereotypy

The treatment of behavior maintained by automatic reinforcement (e.g. stereotypy) can present a unique challenge if practitioners cannot control delivery of the maintaining reinforcer. Further, some individuals might engage in stereotypy only when care providers are absent. In the current evaluation, an adolescent boy's hand flapping was demonstrated to occur in the absence of social contingencies and care providers. To reduce the behavior, two treatment strategies were assessed. In the first approach, verbal reminders to refrain from hand flapping were delivered on time‐based schedules. In the second approach (differential reinforcement of other behavior, DRO), we provided access to a preferred item contingent on prespecified time lengths with no hand flapping when the participant was alone in a room. Results of the investigation indicated that the verbal reminders were unsuccessful, whereas the DRO program resulted in near‐zero levels of stereotypy. Copyright © 2002 John Wiley & Sons, Ltd.     

Choice and number of reinforcers

Pigeons were exposed to the concurrent-chains procedure in two experiments designed to investigate the effects of unequal numbers of reinforcers on choice. In Experiment 1, the pigeons were indifferent between long and short durations of access to variable-interval schedules of equal reinforcement density, but preferred a short high-density terminal link over a longer, lower density terminal link, even though in both sets of comparisons there were many more reinforcers per cycle in the longer terminal link. In Experiment 2, the pigeons preferred five reinforcers, the first of which was available after 30 sec, over a single reinforcer available at 30 sec, but only when the local interval between successive reinforcers was short. The pigeons were indifferent when this local interval was sufficiently long. The pigeons' behavior appeared to be under the control of local terminal-link variables, such as the intervals to the first reinforcer and between successive reinforcers, and was not well described in terms of transformed delays of reinforcement or reductions in average delay to reinforcement.     

Effects of increased response effort on self-injury and object manipulation as competing responses

We evaluated the effects of a response-effort intervention on the occurrence of self-injurious hand mouthing and a competing response (object manipulation) with 4 individuals who had profound developmental disabilities. During Phase 1, results of functional analyses showed that all participants engaged in high levels of hand mouthing in the absence of social contingencies, suggesting that the behavior was maintained by automatic reinforcement. In Phase 2, preferred leisure items were identified for participants during assessments in which duration of leisure item manipulation was used as the index of preference. In Phase 3, participants were observed to engage in high levels of hand mouthing and in varying levels of object manipulation when they had free access to their most preferred leisure items during baseline. The effects of increased response effort on hand mouthing and object manipulation were then evaluated in mixed multiple baseline and reversal designs. The response-effort condition was identical to baseline, except that participants wore soft, flexible sleeves that increased resistance for elbow flexion but still enabled participants to engage in hand mouthing. Results showed consistent decreases in SIB and increases in object manipulation during the response-effort condition for all participants. These results suggested that a less preferred reinforcer (produced by object manipulation) may substitute for a more highly preferred reinforcer (produced by hand mouthing) when response effort for hand mouthing was increased. DESCRIPTORS: self-injurious behavior, automatic reinforcement, reinforcer substitutability, response effort     

EFFECTS OF WARNING STIMULI FOR REINFORCER WITHDRAWAL AND TASK ONSET ON SELF-INJURY

Results of a functional analysis of self-injurious behavior (SIB) in a child with autism showed that her SIB was maintained by access to preferred objects and escape or avoidance of task demands. Extinction and noncontingent reinforcement treatments were supplemented by presenting a statement combined with a picture cue at 30-s intervals indicating that a preferred object would be removed or a task would be presented. Warning stimuli in combination with extinction and noncontingent reinforcement reduced SIB to acceptable levels. SIB rates remained comparatively high in a control condition consisting of a 2-min delay to onset of reinforcer removal or task demands.     

The role of temporal intervals on reinforcer accumulation

Animals accumulate reinforcers when they forgo the opportunity to consume available food in favor of acquiring additional food for later consumption. Laboratory research has shown that reinforcer accumulation is facilitated when an interval (either spatial or temporal) separates earning from consuming reinforcers. However, there has been no systematic investigation on the interval separating consuming reinforcers from earning additional reinforcers. This oversight is problematic because this second interval is an integral part of much of the previous research on reinforcer accumulation. The purpose of the current study was to determine the independent contributions of these two temporal intervals on reinforcer accumulation in rats. Each left lever press earned a single food pellet; delivery of the accumulated pellet(s) occurred upon a right lever press. Conditions varied based on the presence of either an intertrial interval (ITI) that separated pellet delivery from the further opportunity to accumulate more pellets, or a delay‐to‐reinforcement that separated the right lever press from the delivery of the accumulated pellet(s). Delay and ITI values of 0, 5, 10 and 20 s were investigated. The delay‐to‐reinforcement conditions produced greater accumulation relative to the ITI conditions, despite accumulation increasing the density of reinforcement more substantially in the ITI conditions. This finding suggests that the temporal separation between reinforcer accumulation and subsequent delivery and consumption was a more critical variable in controlling reinforcer accumulation.     

Reinforcement Probability and Delay as Determinants of Human Impulsiveness

In behavior theory, “impulsiveness” refers to the choice of an immediate, small reinforcer over a delayed, large reinforcer. Such behavior generally is attributed to a reduction in the value of the large reinforcer as a function of the duration of delay. In contrast, social learning theorists have suggested that human impulsiveness can result from a lowered “expectancy” (subjective probability) of reinforcement. Effects of probability and delay were assessed by asking adults to make repeated choices between reinforcement schedules in which the reinforcers were slides of entertainment figures. An immediate, 5-s reinforcer was consistently chosen over an immediate, 40-s reinforcer if the probability of receiving the large reinforcer had previously been low (.20), implying that impulsiveness can occur without time-based discounting. However, reinforcement delay was also influential: Choice between a certain, small reinforcer and an uncertain, large reinforcer varied according to which reinforcer was immediate and which delayed.

     

RISKY CHOICE IN PIGEONS AND HUMANS: A CROSS‐SPECIES COMPARISON

Pigeon and human subjects were given repeated choices between variable and adjusting delays to token reinforcement that titrated in relation to a subject's recent choice patterns. Indifference curves were generated under two different procedures: immediate exchange, in which a token earned during each trial was exchanged immediately for access to the terminal reinforcer (food for pigeons, video clips for humans), and delayed exchange, in which tokens accumulated and were exchanged after 11 trials. The former was designed as an analogue of procedures typically used with nonhuman subjects, the latter as an analogue to procedures typically used with human participants. Under both procedure types, different variable‐delay schedules were manipulated systematically across conditions in ways that altered the reinforcer immediacy of the risky option. Under immediate‐exchange conditions, both humans and pigeons consistently preferred the variable delay, and indifference points were generally ordered in relation to relative reinforcer immediacies. Such risk sensitivity was greatly reduced under delayed‐exchange conditions. Choice and trial‐initiation response latencies varied directly with indifference points, suggesting that local analyses may provide useful ancillary measures of reinforcer value. On the whole, the results indicate that modifying procedural features brings choices of pigeons and humans into better accord, and that human—nonhuman differences on risky choice procedures reported in the literature may be at least partly a product of procedural differences.     

Choice between delayed reinforcers in an adjusting-delay schedule: The effects of absolute reinforcer size and deprivation level

Choice between two reinforcers differing in magnitude and delay was investigated in rats using an adjusting-delay discrete-trials schedule in which the two reinforcers were associated with two levers (A and B). The delay to Reinforcer A (the smaller reinforcer) was always 2 sec, whereas the delay to Reinforcer B was varied in accordance with the distribution of choices in successive blocks of trials. In Experiment 1, the mean delay to the large reinforcer during the last 5 of 60 training sessions was greater when the rats were maintained at 80% than when they were maintained at 90% of their free-feeding body weights. In Experiment 2, the delay to the larger reinforcer was greater when the two reinforcers consisted of one and two 45-mg food pellets than when they consisted of three and six pellets. The results are consistent with a model of “self-control” which posits hyperbolic relations between reinforcer value and reinforcer magnitude, and between reinforcer value and delay of reinforcement.     

THE EFFECTS OF CHOICE ON SELF‐CONTROL

Three adolescents with traumatic brain injury performed a physical therapy task in the absence of programmed consequences or duration requirements. Next, the experimenter gave the participants the options of a smaller immediate reinforcer with no response requirement or a larger delayed reinforcer with a response requirement. Self‐control training exposed participants to a procedure during which they chose between a smaller immediate reinforcer and a progressively increasing delayed reinforcer whose values varied and were determined by a die roll. The participants chose whether they or the experimenter rolled the die. All participants initially demonstrated low baseline durations of the physical therapy task, chose the smaller immediate reinforcer during the choice baseline, and changed their preference to the larger delayed reinforcer during self‐control training.     

Probability and delay of reinforcement as factors in discrete-trial choice.

Pigeons chose between two alternatives that differed in the probability of reinforcement and the delay to reinforcement. A peck on the red key always produced a delay of 5 s and then a possible reinforcer. The probability of reinforcement for responding on this key varied from .05 to 1.0 in different conditions. A response on the green key produced a delay of adjustable duration and then a possible reinforcer, with the probability of reinforcement ranging from .25 to 1.0 in different conditions. The green-key delay was increased or decreased many times per session, depending on a subject's previous choices. The purpose of these adjustments was to estimate an indifference point, or a delay that resulted in a subject's choosing each alternative about equally often. In conditions where the probability of reinforcement was five times higher on the green key, the green-key delay averaged about 12 s at the indifference point. In conditions where the probability of reinforcement was twice as high on the green key, the green-key delay at the indifference point was about 8 s with high probabilities and about 6 s with low probabilities. An analysis based on these results and those from studies on delay of reinforcement suggests that pigeons' choices are relatively insensitive to variations in the probability of reinforcement between .2 and 1.0, but quite sensitive to variations in probability between .2 and 0.     

Enhancing tolerance to delayed reinforcers: the role of intervening activities

Three participants with moderate to profound mental retardation were exposed to choices between an immediate small amount and a delayed larger amount of a preferred reinforcer. All participants initially showed a relatively high preference for the smaller reinforcer, suggesting impulsive choice making. However this preference reversed, suggesting self-control, when the larger reinforcer was available immediately and, over time, its delay was gradually increased. Results highlight the potential utility of incorporating concurrent activities into self-control training paradigms.     

Further examination of factors that influence preference for positive versus negative reinforcement

Factors that influence choice between qualitatively different reinforcers (e.g., a food item or a break from work) are important to consider when arranging treatments for problem behavior. Previous findings indicate that children who engage in problem behavior maintained by escape from demands may choose a food item over the functional reinforcer during treatment (DeLeon, Neidert, Anders, & Rodriguez-Catter, 2001; Lalli et al., 1999). However, a number of variables may influence choice between concurrently available forms of reinforcement. An analogue for treatment situations in which positive reinforcement for compliance is in direct competition with negative reinforcement for problem behavior was used in the current study to evaluate several variables that may influence choice. Participants were 5 children who had been diagnosed with developmental disabilities and who engaged in problem behavior maintained by escape from demands. In the first phase, the effects of task preference and schedule of reinforcement on choice between a 30-s break and a high-preference food item were evaluated. The food item was preferred over the break, regardless of the preference level of the task or the reinforcement schedule, for all but 1 participant. In the second phase, the quality of the break was manipulated by combining escape with toys, attention, or both. Only 1 participant showed preference for the enriched break. In the third phase, choice of a medium- or low-preference food item versus the enriched break was evaluated. Three of 4 participants showed preference for the break over the less preferred food item. Results extend previous research by identifying some of the conditions under which individuals who engage in escape-maintained behavior will prefer a food reinforcer over the functional one.