Per Holth

STIMULUS FAMILIARITY AND THE DELAYED EMERGENCE OF STIMULUS EQUIVALENCE OR CONSISTENT NONEQUIVALENCE

Stimulus equivalence, defined as C-A matching, was tested in 80 adults following training in a matching-to-sample task involving arbitrary A-B and B-C matching. In Experiment 1, 50 subjects, successively assigned to one of five groups, were exposed to specific stimulus material. The stimuli for subjects in the first group were Greek letters only. In the remaining groups, pictures were incorporated as A-, B-, and/or C-stimuli. The probability of equivalence was low when the stimulus material consisted only of Greek letters. For the remaining groups, the probability of equivalence varied considerably depending upon whether the A-, B-, and/or C-stimuli were pictures. The results indicate that seemingly minimal procedural variations can yield markedly differential outcomes not predicted by any existing model. The results also showed that responding gradually may become consistent with a pattern other than the predicted equivalence pattern. Experiment 2 replicated the results of Experiment 1 showing (a) differential probabilities of equivalence in individual subjects, depending upon the configuration of Greek letters and pictures during training/testing, (b) consistent patterns of responding even when the responding was not in accord with equivalence, and (c) higher reaction times to comparison stimuli initially during testing. Probabilities of equivalence increased in a second exposure to the tasks involving only Greek letters, whether or not the subjects were exposed to a task with pictures prior to the second Greek-letter task. Higher reaction times initially during testing may indicate precurrent problem solving behavior prior to the selection of a comparison stimulus. The finding of delayed emergence of consistent responding suggests that even the slightest tendency toward responding that partitions the stimuli into the experimenter-planned equivalence classes may evolve into consistent responding in accord with those classes.

Probability of stimulus equivalence as a function of training design

The present study investigated differential effects of training design on probability of an equivalence outcome. Forty normal adults were assigned to four different groups. Subjects in the first three groups were exposed to a C-A equivalence test directly following linear series (AB and BC), many-to-one (AB and CB), or one-to-many (BA and BC) training, respectively, while the subjects in the fourth group, following linear series training, were exposed to a symmetry test before the C-A test. Three comparison stimuli were used throughout the experiment to minimize effects of control by negative comparisons. Number of subjects showing equivalence were highest following one-to-many training and lowest following linear series training. Several previously suggested explanations of the differential effects of training design are discussed and shown to be unsatisfactory.

Equivalence Outcome in Single Subjects as a Function of Training Structure

Previous studies comparing groups of subjects have indicated differential probabilities of stimulus equivalence outcome as a function of training structure. Both one-to-many (OTM) and many-to-one (MTO) training structures seem to produce stimulus equivalence more often than a linear series training structure. The purpose of the present study was to explore whether or not corresponding differential probabilities of equivalence outcome as a function of training structure can be demonstrated in the performances of single subjects. In Experiment 1, equivalence outcome was tested successively following training according to each of the three training structures. All subjects responded in accord with equivalence following the OTM training structure independent of the training order, except for 1 subject who did not respond in accord with equivalence following neither of the three training structures. Furthermore, 2 subjects demonstrated individual success following both one-to-many and many-to-one training even when they did not demonstrate success following linear series training, while the reverse never happened. In Experiment 2, equivalence outcome was tested successively following training according to a many-to-one and a one-to-many training structure with both 2 and 3 classes of stimuli. The results showed that all subjects responded in accord with equivalence following the OTM training structure, while 2 subjects did not respond in accord with equivalence following the MTO training structure. In Experiment 3, equivalence outcome was tested successively following training according to a many-to-one training structure and one-to-many training structure with both 3 and 4 members in each class. In accord with the results of Arntzen and Holth (1997) the present results indicated a superiority of the one-to-many over alternative training structures as regards the probability of an equivalence outcome. There was no difference in the probability of an equivalence outcome following one-to-many and many-to-one as a function of increasing number of members. The difference in number of comparisons connected to each sample as a consequence of the dissimilarity in the training structures is discussed as a possible explanation for the difference in equivalence outcome.

Reaction Times and the Emergence of Class Consistent Responding: A Case for Precurrent Responding?

Three experiments explored reaction times and the emergence of consistent responding during tests for equivalence following prerequisite conditional discrimination training for the establishment of three 3-member classes. Using a simultaneous testing protocol following linear series training, Experiment 1 investigated differential reaction times to baseline and to test trials, and the consistency of emergent test performances. Only 1 of 10 subjects responded in accord with stimulus equivalence, and 2 subjects responded in accord with other consistent patterns. Reaction times to test trials were longer than to baseline trials, and there was a tendency for lower reaction times to be associated with consistent responding during testing, whether or not the consistent responding was in accord with equivalence. Experiment 2 investigated reaction times and the emergence of consistent responding during training as a function of repeated training and testing. One subject from the previous experiment participated in eight replications with the stimulus materials from Experiment 1 and two replications with a second set of materials. Neither of these produced stimulus equivalence, even after baseline and symmetry test performances were nearly perfect. However, with both sets of materials, reaction times were gradually reduced as responding became consistent with a different pattern during “equivalence” testing. To examine whether the longer reaction times initially during testing are directly relevant to the emergence of consistent responding and, under favorable conditions, stimulus equivalence, the opportunity to respond to comparison stimuli was restricted to 2 s in Experiment 3. The results showed that with the reaction time constriction, none of the subjects responded in accord with equivalence under otherwise favorable conditions, that is, following one-to-many training. A problem-solving interpretation of equivalence formation is suggested.

PROBABILITY OF STIMULUS EQUIVALENCE AS A FUNCTION OF CLASS SIZE VS. NUMBER OF CLASSES

Two experiments were conducted to study stimulus equivalence as a function of class size and number of classes. In the first experiment, equivalence was tested in 50 normal adult subjects following a linear series training structure. Subjects were successively assigned to either of 10 groups, exposed to a specific stimulus material. For subjects in which number of classes increased, up to six, B-stimuli served as pictures, while A-, and C-stimuli were Greek letters, and “equivalence” was tested in CA tests. The A-, B-, and C-stimuli were the same for ail subjects in whom class members increased up to six, where D-, E- and F-stimuli were Greek letters. Following AB, BC, CD, DE, and FE training, FA, EA, FB, FC, EB, DA, FD, EC, DB, and CA “equivalence” tests were run. In the second experiment, a many-to-one training structure was used to study equivalence as a function of increasing class size without increase number of nodes. The results indicate that the probability of equivalence decreased more as function the number of nodes than as a function of number of classes. Reaction times, particularly to the comparison stimuli, generally increased initially during tests, possibly indicating precurrent problem solving behavior prior to the response to a comparison stimulus.

An operant analysis of joint attention and the establishment of conditioned social reinforcers

An operant analysis of joint attention skills suggests that conditioned social reinforcers play a crucial role in shaping and maintaining joint attention skills in typically developing humans. Although joint attention response topographies can be established successfully in children with autism through contrived reinforcers, natural consequences may not maintain the behavior. Hence, treatment of joint attention problems in children with autism may require the establishment of natural social consequences as conditioned reinforcers. The standard procedure for conditioning new reinforcers is the “pairing procedure.” However, clinical observations suggest that a pairing procedure may not be particularly effective. The current study compared the “pairing procedure” with an explicit operant discrimination procedure. First, a previously neutral stimulus was established as discriminative stimulus for a response that produced a reinforcer, and then tested for conditioned reinforcer effects when being presented contingent upon an arbitrary response with no additional contingent reinforcers. Second, another previously neutral stimulus was repeatedly paired with a reinforcer, and then tested for conditioned reinforcer effects as in the first procedure. Seven of the eight children completed both sequences, and five of these seven children emitted a markedly higher number of responses when stimuli established as SDs were contingent upon them than when stimuli used in the pairing procedure were response contingent. For the sixth child, the difference in favor of the SD procedure was minor, whereas for the last child, the difference was in the opposite direction. In sum, the results suggest that conditioned reinforcers can be more effectively established through the discriminative stimulus procedure than through simple pairing with an unconditioned reinforcer. Possible implications for joint attention teaching procedures are discussed.

An Operant Analysis of Joint Attention Skills

Joint attention, a synchronizing of the attention of two or more persons, has been an increasing focus of research in cognitive developmental psychology. Research in this area has progressed mainly outside of behavior analysis, and behavior-analytic research and theory has tended to ignore the work on joint attention. It is argued here, on the one hand, that behavior-analytic work on verbal behavior with children with autism needs to integrate the research body on joint attention. On the other hand, research on joint attention should integrate behavior-analytic principles to produce more effective analyses of basic processes involved. An operant analysis of phenomena typically considered under the heading of joint attention is followed by examples of training protocols aimed at teaching joint attention skills, such as social referencing, monitoring, gaze following, and such skills interwoven with mands and with tacts. Finally, certain research questions are pointed out.

Intensive Quality Assurance of Therapist Adherence to Behavioral Interventions for Adolescent Substance Use Problems

This study was a cross-cultural replication of a study that investigated therapist adherence to behavioral interventions as a result of an intensive quality assurance system which was integrated into Multisystemic Therapy (MST). Thirty-three therapists and eight supervisors were block randomized to either an Intensive Quality Assurance or a Workshop Only condition. Twenty-one of these therapists treated 41 cannabis-abusing adolescents and their families. Therapist adherence and youth drug screens were collected during a 5-month baseline period prior to the workshop on contingency management and during 12 months post workshop. The results replicated the previous finding that intensive quality assurance enhanced therapist adherence over workshop, to cognitive-behavioral techniques, but not to contingency management. While the clinical impact of such quality assurance remains to be demonstrated, cannabis abstinence increased as a function of time in therapy, and was more likely with stronger adherence to contingency management, but did not differ across quality assurance interventions.

Symmetry Versus Sequentiality Related to Prior Training, Sequential Dependency of Stimuli, and Verbal Labeling

In matching-to-sample tasks, symmetry is defined by the interchangeability of samples and their corresponding comparison stimuli. The purpose of the present study was to identify sources of both intra- and intersubject variability in the formation of symmetry. In Experiment 1, samples and correct comparison stimuli were selected according to three levels of presumed sequential dependence: (a) letters in alphabetical order (high sequential dependence), (b) letters in alphabetical order, but skipping every other letter (moderate sequential dependence), and (c) Greek letters (no sequential dependence). The subjects were assigned to three groups, starting with a specific level of sequential dependence, and proceeding with ascending or descending levels of sequentiality. The results showed that both stimulus material and task order influenced the probability of responding in accordance with symmetry versus responding in accordance with the sequential relation during the tests. Classes of reported collateral responses correlating with either of the emergent relations were derived from postexperimental interviews. Subjects’ reports of potentially bidirectional verbal classes such as visualizing/naming or repeated naming of sample-comparison combinations correlated with symmetry. Reports of sequentially related responding as in naming letters in alphabetical order correlated with test responding in accordance with the sequential relation. In a second experiment, the subjects were specifically instructed to engage in responses pertaining to the derived classes in successive blocks of repeated exposures to the same matching-to-sample task. The results of Experiment 2 showed that when the subjects complied with instructions to engage in bidirectional verbal sequences, they also responded in accordance with symmetry. When subjects complied with instructions to engage in unidirectional verbal sequences, they responded in accordance with sequence during the tests.

Bridging the Gap between Science and Practice: The Effective Nationwide Transport of MST Programs in Norway.

ABSTRACT The successful nationwide transport and evaluation of Multisystemic Therapy (MST) programs in Norway is described. This description is provided within the context of the nations movement towards the adoption of evidence-based practices (EBPs) during the past decade, the conduct of a multisite randomized clinical trial to examine the effectiveness of MST in Norway, and the development of a center for effectively implementing and researching EBPs for child and adolescent problems. Data on Norwegian adolescent substance use, treatment, and research is summarized. Finally, challenges that have been addressed and overcome in achieving the large-scale adoption and implementation of MST are presented from the context of innovation diffusion. System-level barriers and strategies regarding funding, practice norms, local ownership, engaging stakeholders, geography, referral gatekeepers, and risk assessment are noted, as are practitioner level barriers and strategies regarding language, cultural appropriateness, caseload and compensation issues, and background and skill deficits. The Norwegian approach, in many ways, serves as an excellent model for importing and sustaining EBPs on a large-scale basis.