THE INFLUENCE OF CHILD-PREFERRED ACTIVITIES ON AUTISTIC CHILDREN'S SOCIAL BEHAVIOR

One of the characteristics of autistic children is severe social avoidance behavior. We assessed whether the type of activity (child-preferred vs. activities that were arbitrarily determined by an adult) engaged in during an interaction was correlated with the amount of social avoidance behaviors these children exhibit. Results revealed a negative correlation between appropriate child-preferred activities and social avoidance behavior. Additional analyses revealed that (a) social avoidance behaviors could be manipulated within a reversal design, and would predictably decrease when the children were prompted to initiate appropriate child-preferred activities; and (b) these procedures could be used to teach children to initiate child-preferred activities in community settings, resulting in reductions in social avoidance responses even after the therapist's prompts were completely removed. These data suggest that the manipulation of task variables may influence the severe social unresponsiveness that is characteristic of autistic children.     

Relative durations of conditioned stimulus and intertrial interval in conditioned suppression.

The effects of the relative durations of the conditional stimulus and the intertrial interval on bar pressing during a conditioned-suppression procedure were examined as a function of two additional variables--type of operant baseline schedule and rate of shock presentation. In Experiment 1, response suppression was compared across components of a multiple fixed-ratio, random-ratio, fixed-interval, random-interval schedule, at relative conditioned-stimulus/intertrial-interval durations of 1/1, 1/4, and 1/9. In Experiment 2, relative conditioned-stimulus/intertrial-interval duration (1/5, 3/3, or 5/1) was manipulated across groups, while shock frequency (2, 6, or 10 shocks/hr) was manipulated within groups. In both experiments, suppression during the signal was virtually complete at all relative durations. Responding was also suppressed during the intertrial interval, but that suppression varied as a function of experimental manipulations. In Experiment 1, intertrial-interval response rates were higher when relative signal duration was 1/9 than when it was 1/1, although both relative signal duration and shock frequency, which covaried, could have contributed to the difference. In Experiment 2, the patterning of response rates between successive shocks was affected by relative duration, absolute rates during the intertrial interval varied as a function of shock frequency, and differences between suppression during the signal and suppression during the intertrial interval were affected by both relative duration and shock frequency. The data support an analysis based upon relationships between shock-correlated and intertrial-interval stimuli and, as assessed by the relative-delay-to-reinforcement metric, are comparable to results that have been reported from experiments using similar manipulations under the autoshaping paradigm.     

Choice: Effects of changeover schedules on concurrent performance

The components of concurrent schedules were separated temporally by placing interval schedules on the changeover key. The rates of responding on both the main and changeover keys were examined as a function of the reinforcement rates. In the first experiment, the sensitivity of main-key performance to changing reinforcement rates was inversely related to the temporal separation of components, and changeover performance was monotonically related to the ratio of the reinforcement rates. In the second experiment, when the ratio of the reinforcement rates was scheduled to remain constant while the frequency of reinforcement was varied, changeover performance did not remain constant. A “sampling” interpretation of changeover responding was proposed and subsequently tested in a third experiment where extinction was always scheduled in one component and the frequency of reinforcement was varied in the second component. It was concluded that changeover performance can be interpreted using molar measures of reinforcement and that animals sample activities available to them at rates which are controlled by relative reinforcement rates.     

Operant and nonoperant vocal responding in the mynah: Complex schedule control and deprivation-induced responding

Several recent studies have been concerned with operant responses that are also affected by nonoperant factors, (e.g., biological constraints, innate behavior patterns, respondent processes). The major reason for studying mynah vocal responding concerned the special relation of avian vocalizations to nonoperant emotional and reflexive systems. The research strategy was to evaluate operant and nonoperant control by comparing the schedule control obtained with the vocal response to that characteristic of the motor responses of other animals. We selected single, multiple, and chain schedules that ordinarily produce disparate response rates at predictable times. In multiple schedules with one component where vocal responding (“Awk”) was reinforced with food (fixed-ratio or fixed-interval schedule) and one where the absence of vocal responding was reinforced (differential reinforcement of other behavior), response rates never exceeded 15 responses per minute, but clear schedule differences developed in response rate and pause time. Nonoperant vocal responding was evident when responding endured across 50 extinction sessions at 25% to 40% of the rate during reinforcement. The “enduring extinction responding” was largely deprivation induced, because the operant-level of naive mynahs under food deprivation was comparable in magnitude, but without deprivation the operant level was much lower. Food deprivation can induce vocal responding, but the relatively precise schedule control indicated that operant contingencies predominate when they are introduced.     

Maintenance of responding by squirrel monkeys under a concurrent shock-postponement, fixed-interval shock-presentation schedule.

A chain-pulling response was initially developed under a shock-postponement (avoidance) schedule with two squirrel monkeys. Few responses occurred on a lever where responding initially had no scheduled consequence or, subsequently, when a 3-minute fixed-interval shock-presentation schedule was concurrently arranged for lever responses. Appropriate rates and patterns of lever responding developed and were later maintained under the fixed-interval 3-minute shock-presentation schedule alone when the chain and shock-postponement schedule were removed. When both the shock-postponement and shock-presentation schedules were again simultaneously in effect, steady rates of chain pulling were maintained by the shock-postponement schedule and positively accelerated rates and patterns were maintained on the lever by the shock-presentation schedule. Response rates under both schedules were directly related to shock intensity. A history of exposure to a shock-postponement schedule, even though with a topographically different response and manipulandum, was sufficient for the development and eventual maintenance of responding by the presentation of shock. Further, differential performances can be maintained simultaneously by the presentation and postponement of electric shock.     

Some tests of response membership in acquired equivalence classes

Pigeons were trained on many-to-one matching in which pairs of samples, each consisting of a visual stimulus and a distinctive pattern of center-key responding, occasioned the same reinforced comparison choice. Acquired equivalence between the visual and response samples then was evaluated by reinforcing new comparison choices to one set of samples, and examining generalization of these choices to the other samples. Three separate experiments found no evidence of such generalization, as indexed by performance on class-consistent versus class-inconsistent tests. Other tests showed that the pigeons' center-key response patterns during training had indeed served as a conditional cue for choice. These results do not support the hypothesis that different defined responses can become members of acquired equivalence classes.     

Habituation To The Reinforcer May Contribute To Multiple-schedule Behavioral Contrast

Habituation to the reinforcer may contribute to multiple-schedule behavioral contrast. According to this argument, reducing reinforcers in one component of a multiple schedule reduces habituation to the reinforcer. Reducing habituation enhances the value, or effectiveness, of the remaining reinforcers, producing positive contrast. Enriching the reinforcers in one component increases habituation to that reinforcer. Increasing habituation decreases the effectiveness of the reinforcer, producing negative contrast. Such an idea is simple and parsimonious. It is not contradicted by any well-established finding in the contrast literature. It makes several tested and untested predictions that are unusual. However, habituation cannot explain all contrast. A complete explanation requires postulating that at least one additional mechanism, controlled by the conditions of reinforcement in the following component, also contributes to contrast.     

TO WAIT OR TO RESPOND?

Emitting a certain response and waiting for a specified time without making that response had the same consequence. In Experiment 1, food-deprived pigeons were as likely to wait as to respond only if waiting provided food at a much higher frequency than did pecking. In Experiment 2, the consequence for humans was a brief light flash and tone. People were not biased for responding over waiting. Instead, their choices suggested crude payoff maximization. In Experiment 3, pigeons again obtained food, but they were not food deprived and could eat freely at each opportunity. Their behavior was more like that of the humans of Experiment 2 than that of food-deprived pigeons given small quantities of food at each feeding opportunity. The three experiments together showed that biases for responding over waiting were neither inherent characteristics of species nor inevitable outcomes of particular schedules. Choice between active search and waiting depended on ecological–motivational factors even when species and schedules were held constant.     

Reinforcement of probe responses and acquisition of stimulus control in fading procedures

Stimulus control of pigeons' key pecking was transferred from colors to lines by the method of stimulus fading. Fading was conducted with the addition of probes consisting of the line stimuli presented alone at each fading level. Probe responding was used to measure stimulus-control acquisition by the lines. Effects of reinforcement and nonreinforcement of probe responding upon acquisition of stimulus control were assessed using a single-organism repeated-acquisition design in which three fades were conducted serially. Probe responding was not reinforced in the first and third fade but was in the second. Reinforcement of probe responding substantially reduced the number of fading levels needed to complete fading. The outcome of a control experiment ruled out the possibility of accounting for these results in terms of the specific stimuli used in each fade or in terms of the sequential exposure to the three discriminations. Although probes permitted measurement of stimulus-control acquisition in fading, a measurement/acquisition interaction was also present.     

Using a taped intervention to improve kindergarten students' number identification

A multiple baseline design across students was used to evaluate the effects of a taped numbers (TN) intervention on the number‐identification accuracy of 4 kindergarten students. During TN, students attempted to name the numbers 0 through 9 on randomized lists before each number was provided via a tape player 2 s later. All 4 students showed immediate increases and reached 100% in number‐identification accuracy. One student reached 100% accuracy after TN was supplemented with performance feedback, reinforcement, and overcorrection.