ASSESSING STIMULUS CONTROL IN NATURAL SETTINGS: AN ANALYSIS OF STIMULI THAT ACQUIRE CONTROL DURING TRAINING

When a learner is taught a new response, the stimuli that influence its display are often unknown. The presence or absence of these stimuli alters the probability of occurrence of the response. By identifying the stimuli influencing the probability of newly acquired responses, interventionists may program for their generalization more effectively and efficiently. This investigation describes the application of an operant methodology to assess functional relationships between responses and specific stimulus variables. Four young adults with moderate mental retardation were taught to include “please” as part of requests they made in school. Four environmental stimuli, present during training, were assessed for the controlling properties they acquired. Each of the four was assessed prior to and after training by presenting it in isolation (i.e., the other three were varied). If the presence of a single stimulus associated with training did not occasion “please,” then pairs of stimuli were probed. The results revealed that single-stimulus probing occasioned responding by only 1 learner; paired-stimulus probing set the occasion for including “please” by 2 others. Control of the 4th learner's responding was lost before training was introduced, because he began including “please” in his requests during baseline. The implications of these results are discussed in terms of analyzing stimulus control and promoting stimulus generalization.     

STIMULUS CONTROL IN THE CLASSROOM AS A FUNCTION OF THE BEHAVIOR REINFORCED

Eight fifth- and sixth-grade children with behavior problems performed in a classroom under three conditions: (1) unreinforced baseline, (2) reinforcement for being on task, and (3) reinforcement for the accuracy and rate of math problems solved. The teacher was absent for a portion of the class session under each of these conditions. In the teacher's absence, on-task behavior declined markedly and disruption markedly increased, regardless of the reinforcement condition in operation. In addition, the teacher's absence resulted in fewer problems attempted and decreased accuracy. However, the extent to which the children became disruptive was reduced and the number of problems attempted increased when reinforcement was contingent on academic accuracy and rate, instead of being contingent on being on task. The results suggest that by providing contingencies for the products of a child's classroom activities, rather than for being on task, the child will become more independent of the teacher's presence, and more under the control of the academic materials.     

SETTING GENERALITY AND STIMULUS CONTROL IN AUTISTIC CHILDREN1

This study was designed to assess the transfer of treatment gains of autistic children across settings. In the first phase, each of 10 autistic children learned a new behavior in a treatment room and transfer to a novel extra-therapy setting was assessed. Four of the 10 children showed no transfer to the novel setting. Therefore, in the second phase, each child who failed to transfer participated in an analysis of stimulus control in order to determine the variables influencing the deficit in transfer. Each of the four children who did not transfer were selectively responding to an incidental stimulus during the original training in the treatment room. Utilizing a reversal design, each of the four children responded correctly in the extra-therapy setting when the stimulus that was functional during training was identified and introduced into the extra-therapy setting. The extreme selective responding and the resulting bizarre stimulus control found are discussed in relation to the issue of setting generality of treatment gains.     

TEACHERS' GENERALIZED USE OF DELAY AS A STIMULUS CONTROL PROCEDURE TO INCREASE LANGUAGE USE IN HANDICAPPED CHILDREN

In Experiment 1, classroom teachers were taught to delay their offers of help in naturally occurring situations, and thereby to provide additional opportunities for language use by six moderately retarded language-delayed children. The teachers introduced this delay technique in a multiple-baseline design across the six children. As delays were used, child verbal initiations increased. Follow-up assessment showed that teachers were maintaining greater than baseline levels of the delay technique after 10 weeks. Experiment 2 replicated the findings of Experiment 1, and included a more thorough maintenance assessment, while focusing on teachers' generalization of the delay technique. Teachers were found to generalize their use of delay to 56% of their monitored untaught opportunities. The two experiments show that (a) the delay technique is quick to teach and simple to implement, (b) delays do provide opportunities for children to initiate, (c) teachers can generalize their use of delay to novel self-selected situations, and (d) teachers can maintain their use of delays over time.     

WITHIN‐SUBJECT REVERSIBILITY OF DISCRIMINATIVE FUNCTION IN THE COMPOSITE‐STIMULUS CONTROL OF BEHAVIOR

According to the composite-stimulus control model (Weiss, 1969, 1972b), an individual discriminative stimulus (S^D) is composed of that S^D''s on-state plus the off-states of all other relevant S^Ds. The present experiment investigated the reversibility of composite-stimulus control. Separate groups of rats were trained to lever-press for food whenever a tone or a light S^D was present. For one group, the nonreinforced S^Δ condition was tone-and-light absence ($\bar{T}$+$\bar{L}$). Tone-plus-light (T+L) was S^Δ in the other group. On a “stimulus compounding” test that recombined composite elements, maximum responding occurred to that composite consisting only of elements occasioning response increase. That was T+L for the group trained with $\bar{T}$+$\bar{L}$ as S^Δ and $\bar{T}$+$\bar{L}$ for the group trained with T+L as S^Δ. The S^Δ composite was next reversed over groups in Phase 2. In Phase 2 tests, maximum responding that was comparable in magnitude to that of Phase 1 was again controlled by the composite consisting only of elements most recently occasioning response increase—whether T+L or $\bar{T}$+$\bar{L}$. The inhibitory conditioning history of both composite-elements currently occasioning responding did not weaken the summative effect. These results confirm and extend Weiss''s composite-stimulus control model, and demonstrate that such control is fully reversible. We discuss how translating conditions of the stimulus-compounding paradigm to a composite continuum creates a functional and logical connection to intradimensional control measured through stimulus generalization, reducing the number of different behavioral phenomena requiring unique explanations.     

A STIMULUS CONTROL ANALYSIS OF THE PICTURE-WORD PROBLEM IN CHILDREN WHO ARE MENTALLY RETARDED: THE BLOCKING EFFECT

Conditioning to one member of a compound stimulus can be blocked by the presence of a second member to which the response was previously conditioned. This account of selective stimulus control can be used to explain the finding that pictures inhibit learning of written words if the relevant pictures and their verbal equivalents have been paired previously. We tested the blocking explanation of the picture-word problem with 8 mentally retarded students. Following baseline, each student was presented daily with four conditions in an alternating treatments design. In Condition A (blocking), a picture was presented alone and then was followed by the presentation of a picture and written word compound stimulus; in Condition B (blocking/control), a word was presented alone; in Condition C (blocking minimized), a word was enhanced in size and presented alone followed by the word and a picture; and, in Condition D (blocking minimized/control), the enhanced word was presented alone. Each stimulus was presented for 15 s. All students had the lowest percentage of words read correctly in the blocking condition, and all improved when blocking was minimized. Six of 8 students reached their highest percentage of words read correctly in the two control conditions when the words were presented as a single stimulus without pictures. These results indicate that pictures inhibit some students' learning of new words; this may be due to the blocking of conditioning to written words by prior conditioning to pictures.     

A SCATTER PLOT FOR IDENTIFYING STIMULUS CONTROL OF PROBLEM BEHAVIOR

Line graphs that average response frequency over long periods obscure the major rate changes that indicate sources of behavioral control. A scatter plot can make patterns of responding identifiable and, in turn, suggest environmental features that occasion undesirable behavior. Use of scatter diagrams is illustrated in three cases.     

THE FORMATION OF VISUAL STIMULUS EQUIVALENCES IN CHILDREN

Four normal children were presented a series of matching-to-sample tasks, using five sets of visual stimuli designated A, B, C, D, and E. Stimulus equivalences were established by matching stimuli from one set to those from another set. Each set consisted of three stimuli, so matching set A to set D meant that each stimulus in set A served as a sample with all three stimuli in set D as comparisons. Subjects were first taught AD and DC matching and were then able to perform AC/CA matching without additional training. After ED was taught directly, CE/EC and AE/EA performances emerged. Following CB training, three new equivalences were demonstrated: AB/BA, EB/BE, and DB/BD. Oral naming of each stimulus showed that subjects had not assigned a common label to stimuli in the same class, indicating that naming is not necessary for the formation of stimulus equivalences. The absence of response mediation suggests that matching to sample can form direct stimulus-stimulus associations. The data also provide support for the notion that generative performances are outcomes of existing stimulus-control relationships.     

GENERALIZATION OF NAMING RESPONSES TO OBJECTS IN THE NATURAL ENVIRONMENT AS A FUNCTION OF TRAINING STIMULUS MODALITY WITH RETARDED CHILDREN

Picture-cards, photographs, and real objects were compared as training stimuli in order to determine which best facilitated the generalization of naming responses learned in a special training room to real objects in the natural environments of four retarded children. The amount of transfer of naming behavior between the three stimulus modes and the average amount of training time required per stimulus mode were also assessed. Three of the four children displayed considerably more generalization to the real objects in the natural environment when they were trained with real objects. The fourth child displayed substantial generalization regardless of the training stimulus mode. No particular training stimulus mode clearly facilitated the transfer of naming responses to other modes or greatly reduced training time. The results of two supplementary procedures conducted with one child showed that: (1) training in several environments facilitated generalization to real objects in the natural environment when real objects were used as training stimuli but not when picture-cards were used, and (2) transfer from picture-cards to real objects was facilitated by training other picture-cards and the real objects portrayed by them at the same time.     

STIMULUS FADING AND TRANSFER IN THE TREATMENT OF SELF-RESTRAINT AND SELF-INJURIOUS BEHAVIOR

We conducted several manipulations of mechanical restraint properties during the course of treatment for two profoundly retarded adolescents who exhibited both self-restraint and self-injurious behavior. In study 1, a combination of prompting, differential reinforcement, and stimulus fading reduced one subject's self-restraint, which consisted of holding rigid tubes on his arms. Subsequently, stimulus control of both self-restraint and self-injurious behavior was transferred to tennis wrist bands. In study 2, a second subject's self-restraint—placing his hands in his pants—was immediately eliminated by the use of air splints. Additionally, differential reinforcement and air-pressure fading resulted in the complete mobility of his arms and a substantial increase in appropriate behaviors. Results of this investigation suggest that stimulus fading and transfer may be valuable components in the elimination of self-restraint.     

THE USE OF CONTINGENT-INTERRUPTED MUSIC IN THE TREATMENT OF DISRUPTIVE BUS-RIDING BEHAVIOR

The present study evaluated the efficacy of using contingent-interrupted music in treating the disruptive bus-riding behavior of an 8-year-old profoundly retarded female. Music was played during each bus ride as long as the subject was sitting appropriately, and interrupted contingent upon each response defined as disruptive bus riding, during an ABCDCDCDA design. A significant reduction in disruptive bus riding occurred with each introduction of contingent-interrupted music. The treatment procedure described in this report was easy to administer, produced rapid treatment gains, and showed virtually no regression during an 8-week follow-up period.     

STIMULUS GENERALIZATION AND EQUIVALENCE CLASSES: A MODEL FOR NATURAL CATEGORIES

Two three-member classes were formed by training AB and BC using a conditional discrimination procedure. The A and B stimuli were nonsense syllables, and the C stimuli were sets of “short” or “long” lines. To test for equivalence, C1 or C2 was presented as a sample with A1 and A2 as comparisons. Once the class-related comparison was chosen consistently, different line lengths were substituted for the training lines in the CA tests. In general, the likelihood of choosing a given comparison was an inverse function of the difference in the length of the test line from the training line. Stimuli in an equivalence class became functionally related not only to each other but also to novel stimuli that resembled a member of the equivalence class. The combination of primary generalization and equivalence class formation, then, can serve as a model to account for the development of naturally occurring categories.     

PICTURE NAMING,MATCHING TO SAMPLE,AND HEAD INJURY: A STIMULUS CONTROL ANALYSIS

Computer-based procedures were used to examine oral naming and matching-to-sample performances in an adult with a head injury. Relatively few errors occurred when pictures were (a) named, (b) matched to dictated names presented simultaneously, (c) matched to dictation after a delay, and (d) matched to identical pictures presented simultaneously. More errors occurred on delayed than on simultaneous identity matching. On delayed matching trials, fewer errors occurred when instructions to name the samples were given.     

TESTS FOR CONTROL BY EXCLUSION AND NEGATIVE STIMULUS RELATIONS OF ARBITRARY MATCHING TO SAMPLE IN A “SYMMETRY-EMERGENT” CHIMPANZEE

In the present experiments, controlling relations in arbitrary matching-to-sample performance were tested in a 9-year-old female chimpanzee who showed statistically significant emergence of symmetry in previous two-choice conditional discrimination experiments. In Experiment 1, a novel (undefined) sample stimulus was followed by a pair of trained (defined) and undefined comparison stimuli to assess the control by exclusion in arbitrary matching. The chimpanzee selected the undefined shape comparison, excluding the defined one, in color-sample-to-shape-comparison probe trials, although stimulus preferences were relatively stronger than control by exclusion in shape-sample trials. An additional test for control by relations of the sample to the positive comparison (S+ control) showed that her behavior was also under the control of relations of the sample to the positive comparison. In Experiment 2, a defined sample was followed by a pair of negatively defined and undefined comparisons to test control by the relations of the sample to the negative comparison. (S- control). The subject selected undefined comparisons in both color-shape and shape-color test trials. These results clearly indicate that the conditional discrimination behavior of this “symmetry-emergent” chimpanzee was under both S+ and S- control. Furthermore, her performance was also under control by exclusion in color-shape arbitrary matching, unlike other chimpanzees who showed no evidence of symmetry but only S+ control of arbitrary matching.     

THE AVERSIVE CONTROL OF EXCESSIVE ALCOHOL CONSUMPTION BY CHRONIC ALCOHOLICS IN THE LABORATORY SETTING1

The efficacy of several methods of aversive control of excessive alcoholic drinking was investigated in a semi-naturalistic setting that permitted objective measurement of the drinking behavior of chronic alcoholics. Studies 1A and 1B compared an escape-conditioning procedure with a control procedure in which aversive electrical shocks were administered before drinking. Neither procedure effectively decreased subjects' pretreatment, baseline alcoholic drinking behavior. In Study 2, aversive response-contingent shocks effectively suppressed alcoholic drinking, but drinking subsequently returned to its former levels after withdrawal of punishment. Self-administered shock appeared to be as effective as experimenter-administered punishment for controlling drinking, even when the punishment contingency was faded out over time. Study 3 replicated the suppressant effect of punishment, and demonstrated that contingent shock was significantly more effective than yoked, noncontingent shock. A direct comparison of self- versus experimenter-administered punishment suggested a possible slight advantage for the latter.     

USE OF TEXTURE FADING IN THE TREATMENT OF FOOD SELECTIVITY

Children with feeding disorders often display severe food selectivity. For many of these children, consuming highly textured foods may be aversive or potentially dangerous because of frequent gagging. The purpose of this study was to demonstrate the efficacy of texture fading in the treatment of food selectivity displayed by 4 children. Treatment involved the gradual addition of higher textures based on the results of periodic probes. In addition, food acceptance and swallowing were reinforced, while food refusal and food expulsion were placed on extinction. Results showed that all participants successfully advanced to consumption of age-appropriate texture and volume. The results suggest that texture fading with intermittent probes at higher textures may be an effective method for the treatment of food selectivity by texture.     

NAMING,THE FORMATION OF STIMULUS CLASSES,AND APPLIED BEHAVIOR ANALYSIS

The methods used in Sidman's original studies on equivalence classes provide a framework for analyzing functional verbal behavior. Sidman and others have shown how teaching receptive, name-referent matching may produce rudimentary oral reading and word comprehension skills. Eikeseth and Smith (1992) have extended these findings by showing that children with autism may acquire equivalence classes after learning to supply a common oral name to each stimulus in a potential class. A stimulus class analysis suggests ways to examine (a) the problem of programming generalization from teaching situations to other environments, (b) the expansion of the repertoires that occur in those settings, and (c) the use of naming to facilitate these forms of generalization. Such research will help to clarify and extend Horne and Lowe's recent (1996) account of the role of verbal behavior in the formation of stimulus classes.