The merger and development of equivalence classes by unreinforced conditional selection of comparison stimuli

Three experiments assessed the likelihood that subjects with histories of equivalence class development would respond conditionally on new discriminations in the absence of differential consequences for responses. In the first two experiments, two groups of subjects with different experimental histories, but whose performances showed four equivalence classes, responded on trials without explicit reinforcement involving samples from two of the classes and comparisons from the other two classes, in a two-choice matching-to-sample format. Subjects consistently selected a particular comparison in the presence of a particular sample. Subsequent tests showed the emergence of equivalence relations between stimuli from classes linked by the unreinforced conditional selections. Subsequently, in Experiment II, the subjects' responses in the conditional selection trials were reinforced if the selection was reversed from that made previously. Although reversed selection was maintained, 2 of the 3 subjects continued to perform on equivalence relation trials according to their original unreinforced selections. In the third experiment, these 2 subjects responded on a series of conditional discriminations involving three new pairs of sample stimuli and one new pair of comparison stimuli. No explicit reinforcement followed responses on any trial in this experiment. Subsequent tests for equivalence between sample stimuli revealed the development of two equivalence classes.     

Correspondence between definitions and procedures: A reply to Stokes, Osnes, and Guevremont

Stokes, Osnes, and Guevremont's (1987) implicit definition of correspondence classes appears close to ours (Matthews, Shimoff, & Catania, 1987). Their definition, however, is fundamentally procedural and thus may have to be modified as experimental methodologies are refined. The advantage of our contingency-space analysis is that it is independent of specific procedures and focuses attention on problems inherent in some procedural definitions. Specifically, a contingency-space analysis addresses the issue of distinguishing specific instances from classes and reminds us that correspondence can be identified as a class only on the basis of observing a population of opportunities for say/do sequences in which the subject sometimes does not say.     

Intermittent reinforcement of a continuous response

Konorski showed that when a go/no-go procedure was used, sound quality discriminations were rapidly acquired and sound location discriminations were slowly acquired. These findings have been interpreted as a general constraint on the acquisition of auditory discriminations (quality-location effect). However, experiments carried out within an evolutionary framework (Harrison, 1984) have shown that the rate of acquisition of sound location discriminations varies widely as a function of the inclusion or exclusion of naturalistic features. These data suggest that Konorski's findings were a function of the special conditions of the experiments. The first purpose of the present experiments was to assess whether rats showed the effects noted by Konorski when studied under similar conditions. The second purpose was to study the effect of manipulating two natural features (novelty and stimulus-response adjacency) to assess whether the acquisition rates of quality and location discriminations could be greatly modified or made approximately equal, or both. When a go/no-go procedure was used and the other conditions were similar to those of Konorski, rats acquired a quality discrimination but did not acquire a location discrimination. However, when the S+ or S- were presented through a closely adjacent speaker, the sound location discrimination was acquired as rapidly as the quality discrimination. Finally, preexposing the animal to either S+ or S- retarded the rate of or prevented the acquisition of the quality discrimination. The experiments showed that the quality-location effect was determined primarily by the conditions used in Konorski's experiments, and that the effect is not a general constraint on learning.     

Reinforcement probability and ordinal position of response in fixed-interval schedules

Four rats pressed levers and received food pellets under fixed-interval reinforcement schedules of 20, 60, and 180 seconds. The number of responses in each interval was recorded. From these data, the probability of reinforcement was determined as a function of response count. These functions were generally increasing. This finding is consistent with previous suggestions that increasing response rates within fixed intervals may be a function of response count in addition to or instead of elapsed or remaining time.     

Delayed reinforcement and delayed choice in symbolic matching to sample: Effects on stimulus discriminability

Six pigeons were trained to peck a red side key when the brighter of two white lights (S₁) had been presented on the center key, and to peck a green side key when the dimmer of two white lights (S₂) had been presented on the center key. Equal frequencies of reinforcers were provided for the two types of correct choice. Incorrect choices, red side-key pecks following S₂ presentations and green side-key pecks following S₁ presentations, resulted in blackout. With 0-s delay between choice and reinforcement, the delay between sample presentation and choice was varied from 0 to 20 s. Then, with 0-s delay between sample presentation and choice, the delay between choice and reinforcement was varied from 0 to 20 s. Both types of delay resulted in decreased discriminability (defined in terms of a signal-detection analysis) of the center-key stimuli, but delayed choice had more effect on discriminability than did delayed reinforcement. These data are consistent with the view that the two kinds of delay operate differently. The effect of a sample-choice delay may result from a degradation of the conditional discriminative stimuli during the delay; the effect of a choice-reinforcer delay may result from a decrement in control by differential reinforcement.     

The effect of signaled reinforcement availability on concurrent performances in humans

During Phase I, three female human subjects pressed a button for monetary reinforcement in two-component concurrent variable-interval schedules. Five different reinforcement frequencies were used in component A, whereas the reinforcement frequency in component B was held constant. Absolute rates of responding conformed to equations proposed by Herrnstein to describe concurent performances, and the ratios of the response rates and the times spent in the two components conformed to the matching law. During Phase II, the availability of reinforcement in component A was signaled by the illumination of a lamp. This resulted in suppression of response rates in component A and elevation of response rates in component B, these changes being reflected in a distortion of the matching relationship which took the form of a bias in favor of component B.     

Matching models in the analysis of cross-classifications

Inference models motivated by the combinatorial chance literature and the concept of object matching may be used in the analysis of a contingency table if the conditional assumption of fixed row and column totals is imposed. More specifically, by developing a matching reinterpretation for several problems of interest in the prediction analysis of cross-classifications—as defined by Hildebrand, Laing and Rosenthal, appropriate significance tests can be given that may differ from those justified by the more common multinomial models. In the course of the paper the distinction between a degree-1 statistic (based on the relationship between single objects) and a degree-2 statistic (based on the relationship between object pairs) is reviewed in some detail. Also, several specializations are presented to topics of current methodological importance in psychology; for instance, a number of references are made to the measurement of nominal scale response agreement between two raters.Partial support for this research was provided by the National Science Foundation through GSOC-77-28227.     

BEHAVIORAL CONTROL OF MEDICINE COMPLIANCE

This study examined the effectiveness of several behavioral techniques on compliance of college students taking vitamin C on q.i.d. regimen. Compliance was assessed by a new technique using a variation of the urine tracer procedure designed specifically for this study. Subjects were provided vitamin C tablets, with three tablets per week containing phenazopyridine, a drug that produces a bright red-orange urine discoloration. Subjects were requested to indicate when urine discolorations occurred, and compliance was assessed by comparing the time of their report to the time predicted on the basis of the scheduled sequence of vitamin C and phenazopyridine tablets. Baseline compliance was assessed for 72 subjects over a three-week period, with the 40 most noncompliant subjects randomly assigned to four groups for Treatment I. The groups were: self-monitoring, taste, taste and self-monitoring, and a no-treatment control group. The self-monitoring procedure involved recording the time medicine was taken; the taste procedure involved providing the subjects with flavored tablets to increase the saliency of tablet taking; and the self-monitoring and taste procedure involved providing subjects with flavored tablets and asking them to record the flavor of each tablet they ingested. At the end of six weeks, half the subjects in each of these groups participated in response-cost procedures while the remaining subjects continued with their previous procedures. Response-cost procedures were implemented by returning a portion of the subjects' deposit only if a preset compliance criterion was met. Treatment II procedures were implemented for an additional three weeks. Results indicated the self-monitoring and taste plus self-monitoring procedures were superior during Treatment I. The implementation of response cost during Treatment II was associated with a marked improvement in compliance, independent of the history of noncompliance. The effects of the taste plus self-monitoring procedure were maintained during Treatment II and results obtained by this procedure were not significantly different from effects of response cost.