The relationship of self-stimulation to learning in autistic children

The acquisition of discriminative behavior was studied in three autistic children with high-frequency self-stimulatory behavior. It was found that: (a) the children did not acquire the discrimination while engaged in self-stimulation; (b) suppression of self-stimulation produced an increase in correct responding, with eventual acquisition of the discrimination; (c) successful discrimination learning was always associated with a reduction in self-stimulatory behavior, even when aversive stimuli were not used for suppression.     

SELF-STIMULATION AND LEARNING IN AUTISTIC CHILDREN: PHYSICAL OR FUNCTIONAL INCOMPATIBILITY?1

This study investigated whether an observed inverse relationship between self-stimulation and learning in autistic children is due to a physical inability of the subject to use the same body part for self-stimulation and task responding, or whether self-stimulation “distracts” the subject from task responding. Four actively self-stimulating autistic children were taught two discrimination tasks; one required a response that physically interferred with their self-stimulation; the other did not. Results were: (a) all subjects responded similarly across both tasks; (b) the three subjects with higher mental age scores learned both tasks without external suppression of self-stimulation; and (c) none of the subjects showed an inverse relationship between self-stimulation and learning. The study demonstrated that elimination of self-stimulation is not a necessary prerequisite for the acquisition of a new behavior in all autistic children.     

Comparing autistic and normal children along the dimensions of reinforcement maximization, stimulus sampling, and responsiveness to extinction

The purpose of this study was to assess autistic children's ability to maximize reinforcement, sample among available stimuli, and respond to extinction. Responding to five concurrent reinforcement schedules (CRF, FR 2, FR 4, FR 7, and FR 11) was monitored and compared to groups of mental age-matched and chronological age-matched normal children. When a given child consistently selected a given schedule of reinforcement, it was then put on extinction, and both perseveration and responding to the remaining (intact) schedules of reinforcement were monitored. The results showed, first, that while normal children selected the richest schedule of reinforcement, autistics did not maximize reinforcement, typically selecting one of the thinner schedules available. Second, the autistic children sampled less, and less efficiently, than the normal children. Third, the autistic children proved to be much less responsive to extinction, perseverating longer than the normal children before switching to a new reinforcement schedule. Fourth, whenever extinction proved to be a problem in the autistics, it was quickly achieved by a simple change in the stimulus conditions. These results are discussed as possible "keystone" deficits, which may be causally related to many of the behavioral deficits of autism and which might be important target behaviors for treatment.     

INCREASING SPONTANEOUS PLAY BY SUPPRESSING SELF-STIMULATION IN AUTISTIC CHILDREN1

Appropriate play with toys was studied in two autistic children with high occurrences of self-stimulatory behavior. Each child participated in the experimental sessions in an A-B-A design, where “A” refers to baseline sessions and “B” refers to self-stimulation suppression sessions. It was found that: (a) during the baseline sessions, the children exhibited low levels of play and high levels of self-stimulatory behavior; (b) the per cent of unreinforced, spontaneous, appropriate play increased when self-stimulatory behavior was suppressed; and (c) when the suppression of self-stimulation was discontinued, the per cent of self-stimulation and that of appropriate play approached their presuppression levels. These results seem particularly significant because they identify a set of conditions under which spontaneous appropriate behavior, uncommon in autistic children, occurs at an increased level.     

Imitation of Self-Stimulation:

Three autistic children participated in single subject, reversal designs to compare the impact of over correction and adult imitation on self-stimulation. In addition to continuous 10-second observations of frequency of self-stimulation during 10 minute sessions, experimenter and observer also rated the child's mood, attention to the experimenter and quality of attention paid. The order of interventions was randomized fro each subject with baseline preceding each intervention. Although each child's response pattern was unique, the data showed systematic changes in rates of self-stimulation across conditions for two of the children with mean levels of self-stimulation declining during the over correction procedure and increasing during imitation. There were parallel changes in mood and attention with all three children appearing “happiest” and most attentive when their self-stimulatory behavior was imitated by the adult. These results raise interesting possibilities for using adult imitation as a vehicle for establishing a reinforcing relationship with the autistic child.     

Chained and tandem scheduling with children

Children 4 to 7 yr in age were reinforced with trinkets and pennies on chained and tandem schedules. The schedules used were chain DRL FR, chain DRO FR, chain FI FR, tand FI FR, and tand DRO FR. Chain DRL FR and chain DRO FR schedules almost always produced strong schedule and stimulus control, but chain FI FR schedules rarely did if additional techniques were not used. Strong control was produced with chain FI FR schedules, however, if: (a) the FR component was increased in size; (b) schedule and stimulus control was first established with chain DRL FR or chain DRO FR schedules before shifting to the chain FI FR; or (c) an external clock was attached to the FI. Tand FI FR schedules never produced regular or repeatable patterns of responding when additional procedures were not used. Rate patterns resembling those of chain FI FR schedules were produced by tand FI FR schedules, however, if: (a) an external clock was attached to the FI component or (b) control was established by means of tand DRO FR schedules before the tand FI FR was used. Stimulus control was found to be exercised by specific visual stimuli, change of stimuli, and schedule order. Control exercised by schedule order was probably mediated by the child's own behavior which had assumed discriminative stimulus properties.     

Brain-stimulation intensity, rate of self-stimulation, and reinforcement strength: an analysis through chaining

Reinforcement strengths of different intensities of brain stimulation were assessed by means of a two-member behavioral chain. A variable interval schedule of 30 sec was the first-member, and five lever presses, each rewarded with stimulation, was the second. It was found that response rate on the VI schedule continued to increase beyond the intensity value which produced peak rate on the second-member, self-stimulation lever. It was concluded (1) that brain-stimulation reinforcement strength cannot be assessed adequately by means of self-stimulation rate, and (2) the chaining technique employed in the present experiment appears promising as an analytical tool in brain-stimulation research. Finally, some aspects of the data suggested a fatigue or stimulation-adaptation phenomenon.     

DIFFERENTIAL REINFORCEMENT OF CORRECT RESPONSES TO PROBES AND PROMPTS IN PICTURE-NAME TRAINING WITH SEVERELY RETARDED CHILDREN

A systematic sequence of prompt and probe trials was used to teach picture names to three severely retarded children. On prompt trials the experimenter presented a picture and said the picture name for the child to imitate; on probe trials the experimenter did not name the picture. A procedure whereby correct responses to prompts and probes were nondifferentially reinforced was compared with procedures whereby correct responses to prompts and probes were differentially reinforced according to separate and independent schedules of primary reinforcement. In Phase 1, correct responses to prompts and probes were reinforced nondifferentially on a fixed ratio (FR) 6 or 8 schedule; in Phase 2, correct responses to prompts were reinforced on the FR schedule and correct responses to probes were reinforced on an FR schedule of the same value; in Phase 3, correct responses to prompts were reinforced on the FR schedule and correct responses to probes were reinforced on a continuous reinforcement (CRF; every correct response reinforced) schedule; in Phase 4, correct responses to prompts were reinforced on a CRF schedule and correct responses to probes were reinforced on the FR schedule; in Phase 5, a reversal to the conditions of Phase 3 was conducted. For all three children, the FR schedule for correct responses to prompts combined with the CRF schedule for correct responses to probes (Phases 3 and 5) generated the highest number of correct responses to probes, the highest accuracy (correct responses relative to correct responses plus errors) on probe trials, and the highest rate of learning to name pictures.     

Effects of continuous and intermittent reinforcement for problem behavior during functional communication training

We evaluated the effectiveness of functional communication training (FCT) in reducing problem behavior and in strengthening alternative behavior when FCT was implemented without extinction. Following the completion of functional analyses in which social-positive reinforcement was identified as the maintaining variable for 5 participants' self-injurious behavior (SIB) and aggression, the participants were first exposed to FCT in which both problem behavior and alternative behavior were reinforced continuously (i.e., on fixed-ratio [FR] 1 schedules). During subsequent FCT conditions, the schedule of reinforcement for problem behavior was made more intermittent (e.g., FR 2, FR 3, FR 5, etc.), whereas alternative behavior was always reinforced according to an FR 1 schedule. Results showed that 1 participant's problem behavior decreased and alternative behavior increased during FCT when both behaviors were reinforced on FR 1 schedules. The remaining 4 participants shifted response allocation from problem to alternative behavior as the schedule of reinforcement for problem behavior became more intermittent. These results suggest that individuals might acquire alternative responses during FCT in spite of inconsistencies in the application of extinction, although even small errors in reinforcement may compromise treatment effects.     

Cooperative responding in rats maintained by fixed‐ and variable‐ratio schedules

The present study investigated the effects of fixed‐ratio (FR) and variable‐ratio (VR) reinforcement schedules on patterns of cooperative responding in pairs of rats. Experiment 1 arranged FR 1, FR 10, and VR 10 schedules to establish cooperative responding (water delivery depended on the joint responding of two rats). Cooperative response rates and proportions were higher under intermittent schedules than under continuous reinforcement. The FR 10 schedule generated a break‐and‐run pattern, whereas the VR 10 schedule generated a relatively high and constant rate pattern. Experiment 2 evaluated the effects of parametric manipulations of FR and VR schedules on cooperative responding. Rates and proportions of cooperative responding generally increased between ratio sizes of 1 and 5 but showed no consistent trend as the ratio increased from 5 to 10. Experiment 3 contrasted cooperative responding between an FR6 schedule and a yoked control schedule. Coordinated behavior occurred at a higher rate under the former schedule. The present study showed that external consequences and the schedules under which the delivery of these consequences are based, select patterns of coordinated behavior.     

Some determinants of remote behavioral history effects in humans

Undergraduates were exposed to a series of reinforcement schedules: first, to a fixed-ratio (FR) schedule in the presence of one stimulus and to a differential-reinforcement-of-low-rate (DRL) schedule in the presence of another (multiple FR DRL training), then to a fixed-interval (FI) schedule in the presence of a third stimulus (FI baseline), next to the FI schedule under the stimuli previously correlated with the FR and DRL schedules (multiple FI FI testing), and, finally, to a single session of the multiple FR DRL schedule again (multiple FR DRL testing). Response rates during the multiple FI FI schedule were higher under the former FR stimulus than under the former DRL stimulus. This effect of remote histories was prolonged when either the number of FI-baseline sessions was small or zero, or the time interval between the multiple FR DRL training and the multiple FI FI testing was short. Response rates under these two stimuli converged with continued exposure to the multiple FI FI schedule in most cases, but quickly differentiated when the schedule returned to the multiple FR DRL.     

Key pecking during extinction after intermittent or continuous reinforcement as a function of the number of reinforcers delivered during training.

Key pecking by 7 pigeons was established and maintained on a multiple variable-ratio variable-ratio (VR) schedule of food presentation. The schedule in one of the components was then changed to fixed-ratio (FR) 1 for a predetermined number of reinforcers. Both components were then changed to extinction (i.e., multiple extinction, extinction). This sequence was repeated a different number of times for each pigeon to determine the relation between the number of reinforcers delivered during each component of the multiple VR FR 1 schedule and the number of responses during extinction. For most pigeons, there were fewer responses during extinction in the presence of a stimulus recently correlated with FR 1, regardless of the number of reinforcers received. The ratio of the total responses in extinction in the former VR component to the total responses in the former FR 1 component increased as the number of reinforcers delivered during each component of the multiple schedule increased. Within-subject replications of the partial-reinforcement extinction effect generally occurred, and there were no overall reductions in the number of responses in extinction with repeated exposures to extinction.     

EMERGENCE OF REINFORCER PREFERENCE AS A FUNCTION OF SCHEDULE REQUIREMENTS AND STIMULUS SIMILARITY

Tustin (1994) recently observed that an individual's preference for one of two concurrently available reinforcers under low schedule requirements (concurrent fixed-ratio [FR] 1) switched to the other reinforcer when the schedule requirements were high (concurrent FR 10). We extended this line of research by examining preference for similar and dissimilar reinforcers (i.e., those affecting the same sensory modality and those affecting different sensory modalities). Two individuals with developmental disabilities were exposed to an arrangement in which pressing two different panels produced two different reinforcers according to progressively increasing, concurrent-ratio schedules. When two dissimilar stimuli were concurrently available (food and a leisure item), no clear preference for one item over the other was observed, regardless of the FR schedules in effect (FR 1, 2, 5, 10, and 20). By contrast, when two similar stimuli were concurrently available (two food items), a clear preference for one item emerged as the schedule requirements were increased from FR 1 to FR 5 or FR 10. These results are discussed in terms of implications for conducting preference assessments and for selecting reinforcers to be used under training conditions in which response requirements are relatively high or effortful.     

Functional communication during signaled reinforcement and/or extinction

Schedule thinning following functional communication training (FCT) can increase treatment feasibility. Multiple‐schedule arrangements are often used in this process; however, the current literature provides little information on the optimum signal arrangements. In the current study, we examined the effects of three signal arrangements (i.e., signaled FR1, signaled EXT, and signaled FR1/EXT) on rates of problem behavior at dense schedule values and during schedule thinning. At all schedule values, signaled FR1/EXT controlled collateral behavior better than did signaled FR1 or signaled EXT. Additionally, for the single signal arrangements, the signaled FR1 was more efficient than the signaled EXT at dense schedules whereas the inverse was true at leaner schedules. Copyright © 2009 John Wiley & Sons, Ltd.     

Punishment by SD associated with fixed-ratio reinforcement

Two pigeons were trained with positive reinforcement on a multiple FR VI 2 schedule. The VI 2 component was held constant while the FR component was changed from ratios of 1 to 300. After responding had stabilized at each FR value, VI responses produced briefly either the fixed-ratio S^D or a stimulus uncorrelated with either schedule component. Compared to the effects of the uncorrelated stimulus change, the fixed-ratio S^D produced a decrease in VI responding proportional to the size of the FR requirement. It is concluded that stimuli associated with high FR schedules served as punishment for the ongoing behavior.     

Matching-to-sample accuracy on fixed-ratio schedules.

Pigeons performing on a matching-to-sample procedure were exposed to six fixed-ratio (FR) schedules (FR 1, 5, 10, 20, 40, and 60) of food reinforcement for correct matching responses. During both a correction and a noncorrection procedure without an intertrial interval (ITI), matching accuracy was lower on FR 1 and FR 60 than at intermediate ratios. With the FR 1 schedule, both a 5-sec and a 25-sec ITI resulted in higher matching accuracy than without an ITI; accuracy, with an ITI, was fairly constant for ratios of 1 to 20 but declined at higher ratios. The results suggest that the presence or absence of an ITI in matching to sample may account for inconsistencies obtained in earlier studies of the relationship of matching accuracy to ratio size.     

Escape behavior under different fixed ratios and shock intensities

The effects of ratio length and shock intensity on bar pressing were examined in three rats in two escape-from-shock experiments. In Experiment I, shock intensity was held constant while the schedule was varied from FR 1 to FR 20. The latency of the first escape response increased with FR length while the escape rate, computed as over-all rate in shock minus latency of the first response, decreased at FR 20. In Experiment II, the schedule was held constant at FR 5 while shock intensity was manipulated. Latency decreased as intensity increased, while escape rate increased with intensity, passing through a maximum for two subjects. Responses occurring during the last 100 sec of the 2-min escape period decreased as the FR increased for all subjects, and decreased as shock intensity increased for two subjects.     

Exchange schedules in token economies: A preliminary investigation of second‐order schedule effects

Basic research shows that token‐production and exchange‐production schedules in token economies affect each other as second‐order schedules (i.e., the exchange‐production schedule's requirements affect responding toward the token‐production schedule). This relationship has not been investigated with children in academic settings despite the widespread use of token economies in this context. This study compared the effects of fixed‐ratio (FR) and variable‐ratio (VR) exchange‐production schedules of equal ratios (2, 5, and 10) on responding toward an FR 1 token‐production schedule with a child diagnosed with autism. A concurrent chains assessment was also conducted to assess the participant's relative preference for FR and VR exchange‐production schedule arrangements within her typical discrete trial training. Results showed no difference in response rate between the two schedule types. However, the concurrent chains assessment revealed an exclusive preference for the VR arrangement.     

Discriminative and reinforcing properties of two types of food pellets

In Experiment I some discriminative functions of food pellets were studied by developing a multiple schedule of reinforcement (mult FR 30 FI 3) in which the delivery of a standard laboratory food pellet as a reinforcer set the occasion for reinforcement on every 30th response (FR 30), and the delivery of a sucrose food pellet as a reinforcer set the occasion for reinforcement after a 3-min interval (FI 3). Discriminative stimulus control by the type of pellet was also demonstrated by reversing the operant discrimination and having the standard pellet control the FI 3 and the sucrose pellet control the FR 30. In Experiment II a mult FR 30 FR 30 with two bars was developed; a standard food pellet was followed by an FR 30 on Bar 1 and extinction (ext) on Bar 2, while a sucrose pellet was followed by an FR 30 on Bar 2 and ext on Bar 1. A control rat was placed, for comparison, on a mixed (mix) FR 30 FR 30 schedule with two bars, but neither bar correlated with the type of food pellet. In Experiments I and II the similarity between pellet controlled multiple schedules and multiple primed schedules was discussed, as was the comparability of transitions and effectiveness of control between pellet controlled multiple schedules and multiple schedules providing continuous exteroceptive stimuli.     

Some effects of methylphenidate on stimulus control of ratio avoidance behavior in the rat

After exposure to an avoidance schedule which included a warning signal, a rat was placed on a multiple schedule in which the first component was the same as before, i.e., a single response reset the response-shock interval, delaying shock, and the second component differed only in that four bar-presses were required to postpone shock. A fixed ratio requirement of four responses (FR 4) generated behavior resembling a fixed ratio requirement of one response (FR 1) since responding was controlled by the warning signal but more shocks were received. At a dosage of 2 mg/kg, methylphenidate given intraperitoneally decreased shock frequency during FR 4 periods while FR 1 behavior was not affected; at 4 mg/kg, stimulus control of avoidance responding was impaired during both components. Results at 4 mg/kg were partially confirmed by two animals exposed to an FR 4 avoidance schedule which included a warning signal but with different parameters. Response distributions showed that methylphenidate increased response rates in the absence of the warning signal, i.e., stimulus control of ratio-avoidance behavior was impaired although the increased response rates reduced shock frequency. One hour later responses again occurred more frequently during the signal than in its absence but shocks were less frequent than during control (non-drug) periods.