Training intraverbal naming to establish equivalence class performances

The purpose of this three‐experiment study was to evaluate whether performance consistent with the formation of equivalence classes could be established after training adults to tact and intraverbally relate the names of visual stimuli. Fourteen participants were exposed to tact training, listener testing, and intraverbal training (A'B’ and B'C’) prior to matching‐to‐sample (MTS) and intraverbal posttests presented in different sequences across experiments. All participants demonstrated emergent MTS and intraverbal relations consistent with equivalence class formation. More importantly, all participants emitted experimentally defined or self‐generated tacts or intraverbally named the correct sample‐comparison pairs at some point during posttests. These results are consistent with the intraverbal naming account (Horne & Lowe, 1996) in that participants who passed novel relations MTS tests also demonstrated emergence of corresponding intraverbal relations. However, verbal reports and latency data suggest that participants did not necessarily have to use intraverbal naming as a problem solving strategy continuously throughout MTS posttests. These results extended previous research by showing that verbal behavior training of baseline relations (A'B’ and B'C’) is sufficient to establish novel conditional relations consistent with equivalence class formation.     

Incongruous stimulus pairing and conditional discrimination training: effects on relational responding

In Experiment 1, 5 subjects were exposed to a stimulus-pairing procedure in which two nonsense syllables, identified by a letter-number code as A1 and C2, each predicted the onset of a sexual film clip, and the nonsense syllables A2 and C1 each predicted the onset of a nonsexual film clip. Subjects were then exposed to a matching-to-sample test in which the nonsense syllables A1 and A2 were presented as sample stimuli and C1 and C2 were presented as comparison stimuli and vice versa (i.e., C stimuli as samples and A stimuli as comparisons). All subjects matched A1 with C2 and A2 with C1. Subjects were then trained on the conditional discriminations A1-B1, A2-B2, B1-C1, B2-C2, after which the matching-to-sample test was again administered. All subjects continued to match A1 with C2 and A2 with C1 in accordance with the earlier stimulus-pairing contingencies. An additional 5 subjects were exposed first to conditional discrimination training and testing before being exposed to the incongruous stimulus pairing and matching-to-sample testing. Under these conditions, 4 of the 5 subjects always matched A1 with C1 and A2 with C2. Experiment 2 replicated Experiment 1, except that a matching-to-sample test was not administered following the initial training procedure. Under these conditions, matching-to-sample test performances were controlled by the contingencies that had immediately preceded the test. Experiment 3 indicated that initial matching-to-sample test performances were unlikely to change, even after repeated exposure to incongruous training and testing. Experiment 4 demonstrated that pretraining with unrelated stimulus sets increased the sensitivity of matching-to-sample test performances to incongruous contingencies when they were similar in format to those arranged during pretraining. These data may have implications for a behavior-analytic interpretation of attitude formation and change.     

Six-member stimulus classes generated by conditional-discrimination procedures

In conditional-discrimination procedures with three sets of stimuli, A, B, and C, three stimuli per set (A1A2A3, B1B2B3, and C1C2C3), subjects (children and adults) learned to select Set-B and Set-C comparisons conditionally upon Set-A samples (A1B1, A1C1, A2B2, A2C2, A3B3, A3C3). If the conditional-discrimination procedures also generated equivalence relations, three 3-member stimulus classes would be demonstrable, A1B1C1, A2B2C2, and A3B3C3. In addition to these three sets, the present experiments used three other sets of stimuli--D, E, and F. The subjects learned to select Set-E and Set-F comparisons conditionally upon Set-D samples (D1E1, D1F1, D2E2, D2F2, D3E3, D3F3). This established a second group of three 3-member stimulus classes, D1E1F1, D2E2F2, and D3E3F3. In all, two groups of three 3-member classes were established by teaching subjects 12 conditional discriminations. The two groups of 3-member classes were then combined (successfully for 5 of 8 subjects) into a single group of three 6-member classes by teaching the subjects three more conditional relations (E1C1, E2C2, and E3C3). With three other children, enlarging the classes one member at a time also produced 6-member classes. As a consequence of class formation, 60 untrained conditional relations emerged from 15 that had been explicitly taught. Six of the subjects also proved capable of naming the stimuli consistently in accord with their class membership, but two subjects demonstrated class formation even in the absence of consistent naming.     

On the failure and facilitation of conditional discrimination.

Pigeons acquired a conditional discrimination in an autoshaping procedure in which certain stimulus combinations (form plus color) were followed by food, whereas others were not followed by food. Although the discrimination normally was acquired quickly, it was completely prevented when the color elements of the stimulus compounds were presented during the intertrial intervals preceding the trials in which both stimulus elements were available. This failure of discrimination was then prevented by having the colors serve as houselights rather than being localized on the response key and by pretraining procedures in which the colors were utilized in simpler discriminations. The results suggest that stimulus salience plays a critical role in determining whether conditional discriminations will be acquired, as the effects of all of the different operations could be understood in terms of increasing or decreasing the salience of the color elements, above or below some threshold value.     

Conditional acceleration and external disinhibition of operant lever pressing by prereward, neutral, and reinforcing stimuli

Rats responding under a differential-reinforcement-of-low-rate schedule increased their rates of lever pressing during a 20-second click/flash stimulus that preceded the delivery of a response-independent food pellet. The increase could not be attributed to suppression of collateral behavior that has been said to mediate temporally-spaced responding. We propose that the prereward stimulus functioned as an external disinhibitor of lever pressing that had been inhibited by the constraints of the operant schedule. Support is derived from the observed disinhibitory effects of a 10-second unpaired click/flash stimulus and of unsignaled, response-independent pellets that were presented while the animals were responding under the same schedule.     

Microcomputer-based programmed instruction in identity matching to sample for persons with severe disabilities

Three individuals with mental retardation, who had failed to learn identity matching to sample with standard fading and prompting procedures, were given microcomputer-based programmed instruction. The methods were based on an analysis of two features of typical identity matching procedures: (a) within each trial, the current sample stimulus must control comparison selection, and (b) across trials, specific comparison stimuli must function both as S+ and as S–, depending upon the sample presented (conditional discrimination). During the first phase of training, one-trial acquisition of discriminative stimulus control was established in a nonconditional discrimination context where the S+ or S– functions of specific stimuli did not change from trial to trial. After one-trial learning was established, conditional discrimination was programmed by gradually introducing reversals of S+/S– stimulus functions. All three participants learned to perform conditional identity matching. Avenues for further analysis of the prerequisites for conditional discrimination and continued development of programmed methods are discussed.     

The development of functional and equivalence classes in high-functioning autistic children: the role of naming.

The development of functional and equivalence classes was studied in four high-functioning, preschool-aged autistic children. Initially, all subjects failed to demonstrate match-to-sample relations indicative of stimulus equivalence among two three-member classes of visual stimuli. Then, 2 subjects showed emergence of those relations after they were taught to assign the same name to all members in each class. Next, subjects were taught names for new stimuli outside the match-to-sample format. On subsequent match-to-sample tests, 2 subjects demonstrated untrained conditional relations among the stimuli given a common name. New, unnamed stimuli were then related via match-to-sample training to stimuli from sets of named stimuli. Tests for emergent conditional relations between the new unnamed stimuli and the named stimuli yielded positive results for 1 subject and somewhat mixed results for 3 subjects. Finally, without naming, 2 subjects developed stimulus equivalence among two new three-member classes of visual stimuli. These data suggest that naming may remediate failures to develop untrained conditional relations, some of which are indicative of stimulus equivalence.     

Adventitious control by the location of comparison stimuli in conditional discriminations.

In a conditional discrimination procedure, samples appeared in a center key, and comparisons appeared in two of four outer keys. The location of comparison keys varied from trial to trial. Separate learning curves for each of the six possible pairs of comparison keys were plotted in a signal-detection space, revealing different patterns of progress on each pair. Also, when learned conditional discriminations were disrupted, pairs of keys differed in their patterns of disruption. Varying the location of comparison stimuli among six different pairs of keys had not eliminated key position as a controlling aspect of the stimuli. The variations simply increased the number of stimulus compounds--key position and experimental stimuli--that the subject learned. Plotting conditional-discrimination learning curves in a signal-detection space reveals relations among hits, false alarms, accuracy, and comparison preference that help to define a subject's progress.     

Emergent equivalence relations between interoceptive (drug) and exteroceptive (visual) stimuli.

Conditional "if-then" relations between drug (interoceptive) stimuli and visual (exteroceptive) stimuli were taught to 4 normal humans. Interoceptive stimuli were the effects produced by 0.32 mg/70 kg triazolam (a prototypical benzodiazepine) and placebo (lactose-filled capsules); exteroceptive stimuli were black symbols on white flash cards. Following the training of the prerequisite conditional relations, tests of emergent relations were conducted between exteroceptive stimuli and between interoceptive and exteroceptive stimuli. Equivalence relations emerged immediately without explicit training for all 4 subjects. Accuracy of responding during the interoceptive-exteroceptive equivalence tests and subjects' self-reports showed consistent discrimination between the drug effects of triazolam and placebo. Finally, a generalization test assessed whether a novel visual stimulus presented in the context of the placebo (i.e., no drug) would generalize to visual stimuli belonging to the placebo stimulus class. All 3 subjects who completed this test reliably chose the visual stimuli belonging to the placebo class and not the visual stimuli belonging to the triazolam stimulus class. The development of equivalence relations between interoceptive and exteroceptive stimuli demonstrates that private and public stimulus events can emerge as members of the same equivalence class. Theoretical and clinical implications are discussed.