Mark Galizio

10 Stimulus equivalence: A class of correlations, or a correlation of classes?

Publisher Summary The chapter discusses stimulus equivalence and describes experiments in which the reversals of baseline conditional discriminations appear to have different effects across probe trial types (i.e., reflexivity, symmetry, and transitivity/equivalence). It examines other empirical evidence performance on the various probe trial types that may differ in potentially important ways and reviews studies that use measures other than probe trials to assess equivalence-like phenomena. The theme considered throughout is a fundamental one for even the simplest of analytic units. The mathematical definition of equivalence specifies only required test outcomes, not the make-up of the behavioral unit(s) that includes these outcomes. The predictive value of the set theory framework is undeniable, and the structured approach that this framework has provided for the study and training of complex behavioral repertoires, often termed “cognitive,” has yielded impressive results. A definition of equivalence that allowed for correspondence among three independent stimulus control relations provides even greater generality while maintaining the precision and rigor of the set theory framework.

Analyzing the Reinforcement Process at the Human Level: Can Application and Behavioristic Interpretation Replace Laboratory Research?

Critics have questioned the value of human operant conditioning experiments in the study of fundamental processes of reinforcement. Contradictory results from human and animal experiments have been attributed to the complex social and verbal history of the human subject. On these grounds, it has been contended that procedures that mimic those conventionally used with animal subjects represent a “poor analytic preparation” for the explication of reinforcement principles. In defending the use of conventional operant methods for human research, we make three points: (a) Historical variables play a critical role in research on processes of reinforcement, regardless of whether the subjects are humans or animals. (b) Techniques are available for detecting, analyzing, and counteracting such historical and extra-experimental influences; these include long-term observations, steady state designs, and, when variables are not amenable to direct control (e.g., age, gender, species), selection of subjects with common characteristics. (c) Other forms of evidence that might be used to validate conditioning principles—applied behavior analysis and behavioristic interpretation—have inherent limitations and cannot substitute for experimental analysis. We conclude that human operant conditioning experiments are essential for the analysis of the reinforcement process at the human level, but caution that their value depends on the extent to which the traditional methods of the experimental analysis of behavior are properly applied.

Positive and Negative Reinforcement: Should the Distinction Be Preserved?.

Michael (1975) reviewed efforts to classify reinforcing events in terms of whether stimuli are added (positive reinforcement) or removed (negative reinforcement). He concluded that distinctions in these terms are confusing and ambiguous. Of necessity, adding a stimulus requires its previous absence and removing a stimulus its previous presence. Moreover, there is no good basis, either behavioral or physiological, that indicates the involvement of distinctly different processes, and on these grounds he proposed that the distinction be abandoned. Despite the cogency of Michael’s analysis, the distinction between positive and negative reinforcement is still being taught. In this paper, we reconsider the issue from the perspective of 30 years. However, we could not find new evidence in contemporary research and theory that allows reliable classification of an event as a positive rather than a negative reinforcer. We conclude by reiterating Michael’s admonitions about the conceptual confusion created by such a distinction.

Sensation seeking and drug choice.

Sensation Seeking Scale scores were obtained from two groups of drug program clients: polydrug users and opiate and depressant drug users. The major findings were that polydrug users scored higher in sensation seeking than depressant users, and that this effect was independent of demographic differences between groups. These results suggest that the sensation-seeking motive may be a significant factor for polydrug, but not depressant, abuse patterns.

Sensation seeking, reinforcement, and student drug use

College student volunteers completed the Sensation Seeking Scale, a drug use survey, and provided demographic information. Subjects were also asked to generate a list of the events that they found most reinforcing (Reinforcer List). Drug use was positively related to scores on all subscales of the Sensation Seeking Scale. Although neither drug use nor sensation seeking scores were related to the total number of items generated on the Reinforcer List, drug users did generate a higher percentage of items rated as high sensation producing items, and percent high sensation reinforcers was correlated with scores on the Sensation Seeking Scale. These results illustrate the importance of the sensation seeking motive as a correlate of student drug use.

Effects of dizocilpine (MK801) on olfactory span in rats.

NMDA receptor antagonists interfere with learning and memory in some tasks, but not others. Some recent accounts have suggested that tasks placing demands on working memory are those most likely to be affected, and the present study tested this hypothesis. The purpose of the study was to adapt a recently developed procedure designed to test working memory capacity, the olfactory memory span task, for use in behavioral pharmacology and to then determine the effects of the NMDA receptor antagonist, dizocilpine (MK801) on performance in this task. Rats were trained in a non-match-to-sample procedure under conditions in which they had to remember an increasing number of olfactory stimuli as the session progressed. Simple olfactory discrimination trials were interspersed to provide a performance control. Effects of dizocilpine (.03, .10, .17, .3mg/kg) were determined after stable performances were obtained. Rats were able to sustain stable performances on both the span and simple discrimination tasks with average spans of about 10 items. Accuracy declined as the number of stimuli to remember increased, and dizocilpine impaired accuracy in a dose-dependent and memory-load dependent fashion. The finding that the effects of dizocilpine interacted with the number of stimuli to remember is generally consistent with hypotheses linking NMDA receptors and working memory processes.

Clustering in artificial categories: an equivalence analysis.

Category clustering is a robust finding in the free recall of familiar category members, but has rarely been studied with artificial categories. In the present study, college students learned artificial categories via stimulus-equivalence methodology. Arbitrary match-to-sample training with nonsense syllables established three interrelated conditional discriminations, and, for most subjects, unreinforced test trials revealed the emergent stimulus-control relations considered to be evidence of equivalence classes. Free-recall tests revealed evidence of significant within-class clustering both before and after equivalence testing, but was more pronounced after the equivalence tests. These findings confirm that classic phenomena like clustering in free recall can be studied with stimulus-equivalence methodology, thus allowing for experimental control over relevant variables.

The abstracted operant: A review of relational frame theory: A post-skinnerian account of human language and cognition.

Hayes, Barnes-Holmes, and Roche (2001) have edited a series of tightly integrated articles that present the relational frame theory (RFT) approach to the study of complex human behavior. The book provides a well-elaborated account of RFT and reviews the literature on stimulus relations that bears on the approach. Several articles examine extensions of RFT to a variety of issues ranging from language and cognition to psychotherapy and religion, and these provide illustrations of the comprehensiveness of the approach. Although RFT is a paradigm developed within the behavioral tradition, it is not a traditional behavioral paradigm, and thus has been controversial. Problems and puzzles in the study of stimulus relations and research directions needed for their solution are considered.

Acquisition in the Morris swim task is impaired by a benzodiazepine but not an NMDA antagonist: A new procedure for distinguishing acquisition and performance effects

The problem of learning versus performance continues to challenge researchers interested in drug effects on place learning and memory. To address this problem, the present study adapted the repeated acquisition/performance (RAP) procedure to the Morris swim task. The procedure involved training subjects to swim to a hidden platform that was always in the same location in one pool and in a new location each day in another pool. The advantages of this procedure are that acquisitions of new place responses and performances of previously learned place responses can be directly compared in individual subjects within single sessions, and dose–response functions can be determined for each individual subject. Experiment 1 demonstrated the ability of rats to learn new platform locations in one pool while maintaining stable performance on a previously learned place response in another pool within individual sessions. Experiment 2 used the RAP adaptation of the Morris swim task to study effects of chlordiazepoxide (CDZ), a benzodiazepine, and dizocilpine (DZP; a noncompetitive N-methyl-d-aspartate antagonist), on place learning and performance. Both drugs impaired performance in a dose-dependent manner. More interestingly, a moderate dose (10 mg/kg) of CDZ caused a small but reliable acquisition impairment without affecting performance of the previously learned place response. Doses of DZP that were substantially greater than doses previously shown to disrupt induction of NMDA-dependent long-term potentiation in the hippocampus did not impair acquisition in this procedure. Acquisition was affected only at DZP doses that also impaired the performance measure.

Human postdiscrimination gradients: The effects of three-stimulus discrimination training

Young adult subjects were trained in a discrimination involving three pure tones varying in pitch, with two positive stimuli and a negative stimulus located midway between the two. Subjects in the control conditions were trained only with the two positive stimuli. Generalization gradients were bimodal in all cases, but for the control subjects, the modes were at the positive stimulus values, while postdiscrimination gradients were displaced away from the negative stimulus toward the extremes of the continuum. Since, with this procedure, the training and test adaptation levels were the same, the observed displacements are difficult to explain in terms of an adaptation-level account of peak shifts. The observed shifts are more consistent with the conditioning-extinction model which assumes interactions between inhibitory and excitatory gradients. However, overall response rates did not reflect the action of summation processes.