EFFECTS OF DIFFERENTIAL REINFORCEMENT ON THE GENERALIZATION OF A REPLACEMENT MAND IN THREE CHILDREN WITH SEVERE LANGUAGE DELAYS

We investigated variables that may influence the generalization of a replacement mand in 3 young children with severe language delays. A multiple baseline design consisting of one stimulus class of manding opportunities that we arbitrarily divided into three categories (i.e., food, toys, and events) was used for each child. During baseline probes, all children manded mainly by reaching, grabbing, or leading. We then taught each child a replacement mand using a single member of the stimulus class. Acquisition of the replacement mand occurred under highly restricted conditions in a setting that was completely isolated from the generalization settings. Postacquisition probes revealed almost exclusive use of old manding forms. Subsequently, extinction of the old forms and reinforcement of the replacement mand were introduced in a sequential fashion. Two children manifested a substantial increase, and 1 child displayed a moderate increase in the occurrence of the replacement mand (i.e., generalization occurred). These results suggest that a differential reinforcement procedure can alter the probability of the occurrence of response class members across a variety of stimulus conditions.     

Effects of reinforcement rate and delay on the acquisition of lever pressing by rats.

The acquisition of lever pressing by naive rats, in the absence of shaping, was studied as a function of different rates and unsignaled delays of reinforcement. Groups of 3 rats were each exposed to tandem schedules that differed in either the first or the second component. First-component schedules were either continuous reinforcement or random-interval 15, 30, 60 or 120 s; second-component schedules were fixed-time 0, 1, 3, 6, 12, or 24 s. Rate of responding was low under continuous immediate reinforcement and higher under random-interval 15 s. Random interval 30-s and 60-s schedules produced lower rates that were similar to each other. Random-interval 120 s controlled the lowest rate in the immediate-reinforcement condition. Adding a constant 12-s delay to each of the first-component schedule parameters controlled lower response rates that did not vary systematically with reinforcement rate. The continuous and random-interval 60-s schedules of immediate reinforcement controlled higher global and first-component response rates than did the same schedules combined with longer delays, and first-component rates showed some graded effects of delay duration. In addition, the same schedules controlled higher second-component response rates in combination with a 1-s delay than in combination with longer delays. These results were related to those from previous studies on acquisition with delayed reinforcement as well as to those from similar reinforcement procedures used during steady-state responding.     

Simple and conditional visual discrimination with wheel running as reinforcement in rats.

Three experiments explored whether access to wheel running is sufficient as reinforcement to establish and maintain simple and conditional visual discriminations in nondeprived rats. In Experiment 1, 2 rats learned to press a lit key to produce access to running; responding was virtually absent when the key was dark, but latencies to respond were longer than for customary food and water reinforcers. Increases in the intertrial interval did not improve the discrimination performance. In Experiment 2, 3 rats acquired a go-left/go-right discrimination with a trial-initiating response and reached an accuracy that exceeded 80%; when two keys showed a steady light, pressing the left key produced access to running whereas pressing the right key produced access to running when both keys showed blinking light. Latencies to respond to the lights shortened when the trial-initiation response was introduced and became much shorter than in Experiment 1. In Experiment 3, 1 rat acquired a conditional discrimination task (matching to sample) with steady versus blinking lights at an accuracy exceeding 80%. A trial-initiation response allowed self-paced trials as in Experiment 2. When the rat was exposed to the task for 19 successive 24-hr periods with access to food and water, the discrimination performance settled in a typical circadian pattern and peak accuracy exceeded 90%. When the trial-initiation response was under extinction, without access to running, the circadian activity pattern determined the time of spontaneous recovery. The experiments demonstrate that wheel-running reinforcement can be used to establish and maintain simple and conditional visual discriminations in nondeprived rats.     

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.     

Interspersing Additional Brief, Easy Problems to Increase Assignment Preference on Mathematics Reading Problems

We extended previous research on student preference for academic assignments by presenting college students with a control assignment containing eight, two-digit × two-digit + two-digit × two-digit (2 × 2 + 2 × 2) mathematics reading problems and an experimental assignment that contained eight equivalent, 2 × 2 + 2 × 2 problems plus three additional interspersed four-digit + four-digit mathematics reading problems. After spending 9 min 15 s working on each assignment, significantly more students ranked the experimental assignment as being less difficult and requiring less effort to complete. When given a choice between the two assignments for homework, significantly more students chose the experimental assignment. No differences between assignments were found on target problem (i.e., 2 × 2 + 2 × 2) accuracy levels. Results support earlier research that showed how students' preference for assignments could be improved by interspersing additional brief tasks among more time consuming target tasks. In addition to applied implications, theoretical implications related to task completion as a reinforcing event, choice, and relative rates of reinforcement are discussed.     

Functional Analysis and Treatment of Mealtime Problem Behavior for a Person with Developmental Disabilities

We conducted a functional analysis of problem behaviors (spitting and whining) during meals and tested an intervention based on that analysis. The participant was a 13-year-old young woman with severe mental retardation and cerebral palsy. She ate all food presented to her, and the hypotheses were tested that the problem behaviors were maintained either by contingent access to trainer attention or the pace of eating. An attention analysis examined the relationship between problem behavior and trainer attention during the meal. The effect of attention following problem behavior versus ignoring was inconclusive. An analysis of the effects of teacher paced eating, student paced eating (reinforce spoon grasping) and food presented for problem behavior was conducted next. Problem behavior rates were highest when access to food was made contingent on the performance of problem behavior and lowest when spoon grasping resulted in a bite of food. Following analysis, an intervention was designed to reduce the frequency of targeted problem behaviors during mealtime. Reinforcing spoon grasping and a 10s removal of food following problem behavior dramatically reduced spitting and whining during meals. The study provides a demonstration of an extended functional analysis and treatment of a complex behavior pattern.     

RESPONDING MAINTAINED BY INTERMITTENT REINFORCEMENT: IMPLICATIONS FOR THE USE OF EXTINCTION WITH PROBLEM BEHAVIOR IN CLINICAL SETTINGS

Results of basic research have demonstrated that behavior maintained on an intermittent schedule of reinforcement (INT) will be extinguished more slowly than behavior maintained on a continuous schedule (CRF). Although these findings suggest that problem behaviors may be difficult to treat with extinction if they have been maintained on INT rather than on CRF schedules, few applied studies have examined this phenomenon with human behavior in clinical settings. The purpose of this study was to determine whether problem behavior maintained on CRF schedules would be extinguished more rapidly than behavior maintained on INT schedules. Three individuals diagnosed with profound mental retardation participated after results of pretreatment functional analyses had identified the sources of reinforcement that were maintaining their self-injury, aggression, or disruption. Subjects were exposed to extinction following baseline conditions with CRF or INT schedules alternated within reversal or multielement designs. Results suggested that problem behaviors may not be more difficult to treat with extinction if they have been maintained on INT rather than CRF schedules. However, switching from an INT to a CRF schedule prior to extinction may lower the baseline response rate as well as the total number of responses exhibited during extinction.     

EFFECTS OF EQUAL AND UNEQUAL REINFORCER DURATION DURING FUNCTIONAL ANALYSIS

In the functional analysis described by Iwata, Dorsey, Slifer, Bauman, and Richman (1982/1994), reinforcer duration varied across conditions (e.g., brief attention vs. 30 s of escape); this may result in unequal exposure to the establishing operations for aberrant behavior. In this study, we compared the effects of unequal and equal reinforcer duration during a functional analysis. The results showed that reinforcer duration affects the rate of aberrant behavior and may potentially alter functional analysis interpretation.     

Effects of reinforcement amount on attack induced under a fixed-interval schedule in pigeons

Key pecking by pigeons was maintained on a chained fixed-interval 4-min (12-min for 1 subject) fixed-ratio 1 schedule of food presentation. Attacks toward a restrained and protected conspecific were recorded. In the first experiment, the amount of food presented per interval was manipulated across phases by varying the number of fixed ratios required in the terminal link of the chain. Measures of attack for all pigeons during the fixed-interval component increased monotonically as a function of food amount. In the second experiment, two different food amounts alternated within each experimental session under a multiple schedule. For both pigeons in this experiment, measures of attack were higher during the component that delivered the larger food amount per interval. The differences in levels of attack induced by the two food amounts in Experiment 2, however, were not as great as in Experiment 1; apparently this was because attack during the first interval of each component was controlled in part (P-5626) or entirely (P-7848) by the reinforcement amount delivered at the end of the previous component. Attack was also a function of the location of the interfood interval within the session. For both pigeons, attack tended to decrease throughout the session. The results of both experiments suggest that attack is an increasing function of reinforcement amount under fixed-interval schedules, but that this function may be influenced by the manner in which reinforcement amount is manipulated, by the duration of the interfood interval, and by the location of the interfood interval within the experimental session. In general, these results are compatible with theories of induced attack and other schedule-induced behavior that emphasize aversive after-effects of reinforcement presentation.     

Human symbolic matching-to-sample performance: Effects of reinforcer and sample-stimulus probabilities

Four experiments, each with 6 human subjects, varied the distribution of reinforcers for correct responses and the probability of sample-stimulus presentation in symbolic matching-to-sample procedures. Experiment 1 held the sample-stimulus probability constant and varied the ratio of reinforcers obtained for correct responses on the two alternatives across conditions. There was a positive relation between measures of response bias and the ratio of reinforcers. Experiment 2 held the ratio of reinforcers constant and varied the sample-stimulus probability across conditions. Unlike previous studies that used pigeons as subjects, there was a negative relation between bias and the ratio of sample-stimulus presentations. In Experiment 3, the sample-stimulus probability and the reinforcer ratio covaried across conditions. Response bias did not vary systematically across conditions. In Experiments 1 to 3, correct responses were reinforced intermittently. Experiment 4 used the same procedure as Experiment 3, but all correct responses now produced some scheduled consequence. There was a positive relation between response bias and the ratio of reinforcers. The results suggest that human performance in these tasks was controlled by both the relative frequency of reinforced responses and the relative frequency of nonreinforced responses.