Formation of new stimulus equivalence classes by exclusion

This study presents three experiments that aimed to show the formation of stimulus equivalence relations among stimuli that had been previously related only by exclusion. In Experiment 1, participants were trained on baseline conditional discriminations to establish two 3‐member equivalence classes. Then, they were exposed to exclusion trials, without feedback, in which undefined stimuli had to be matched by rejecting the defined baseline stimuli. Finally, participants responded to test trials evaluating the emergence of symmetry and transitivity among the undefined stimuli from the exclusion trials. For half of the participants, the stimuli related by exclusion were introduced as S‐ stimuli in the baseline trials, whereas for the other half they were not. Further, half of the participants were assessed for emergent relations with stimuli from all the classes, whereas the other half was assessed for emergent relations with only the stimuli related by exclusion. In Experiment 2, the S‐ comparisons in the emergent relations test trials with stimuli only related by exclusion were stimuli from a null class. In Experiment 3, the number of exclusion trials was doubled. Across experiments, most participants showed emergence of equivalence relations among the stimuli related by exclusion. Some conditions of stimulus control associated with exclusion learning and the emergence of equivalence relations are discussed.     

Equivalence‐based instruction to establish a textual activity schedule in an adult with Down syndrome

Transfer of control from picture to text‐based activity schedules has been shown to occur following conditional discrimination training in children with autism. This study extended this research by evaluating if conditional discrimination training could promote transfer of control in an adult with Down syndrome. The participant was taught to select photographs and pictures of kitchen tools when provided with dictated names. Then, he completed a text‐based activity schedule, matched printed words to photographs, and orally named printed words without direct training.     

Equivalence‐based instruction of academic skills: Application to adolescents with autism

This study evaluated the efficacy of three equivalence‐based instruction procedures on the acquisition of novel academic skills by 3 adolescents diagnosed with autism in a school setting. The skills targeted for instruction were related to topics in history, science, and mathematics, and were taught using different training structures from the PEAK‐E curriculum. All participants demonstrated mastery of the trained relations and the tested derived relations following all variants of equivalence‐based instruction.     

Efficiently establishing concepts of inferential statistics and hypothesis decision making through contextually controlled equivalence classes

Computerized lessons that reflect stimulus equivalence principles were used to teach college students concepts related to inferential statistics and hypothesis decision making. Lesson 1 taught participants concepts related to inferential statistics, and Lesson 2 taught them to base hypothesis decisions on a scientific hypothesis and the direction of an effect. Lesson 3 taught the conditional influence of inferential statistics over decisions regarding the scientific and null hypotheses. Participants entered the study with low scores on the targeted skills and left the study demonstrating a high level of accuracy on these skills, which involved mastering more relations than were taught formally. This study illustrates the efficiency of equivalence-based instruction in establishing academic skills in sophisticated learners.     

A method for studying stimulus class dynamics using budgerigars and vocal responding

We describe a methodology for examining stimulus class dynamics in budgerigars. Three budgerigars served as subjects. Four call types were trained as operant responses to four discriminative stimuli. The birds were over‐trained in this discrimination, and then run through two conditions. In Condition 1 the birds were trained to peck two of the four stimuli when these two stimuli appeared in two novel locations, while continuing to vocalize to all four stimuli when they occurred in the original training location. An analysis of vocal errors showed that the two stimuli assigned to the peck response were more likely to become confused with one another. In Condition 2 the birds experienced symbolic matching‐to‐sample training. Vocal discrimination trials were run concurrently with this training. The observed vocal‐response errors suggest that during a matching‐to‐sample task, sample stimuli became temporarily confused with one another. The results, although primarily intended to illustrate the utility of our method, support the hypothesis that stimuli assigned a common response become more similar, or equivalent, to one another.     

The contextually controlled, feature-mediated classification of symbols

The classification of names of people or objects based on the features acquired by the names and the sorting instructions provided is a commonplace occurrence. For example, given the names Renoir, Pollock, James and Voltaire the average adult would be able to classify them differentially based on the instruction to classify them based on vocation or nationality. In general, such a repertoire reflects the reclassification of symbols (i.e, the names of individuals) in terms of contextual cues (instructions to sort by vocation or nationality) and the features acquired by the symbols (the specific nationalities and vocations). The present experiment studied this phenomenon with the use of arbitrary stimuli that did not have clear preexperimental associations. Two of 4 participants classified the symbols into different equivalence classes based on the prevailing contextual cues and the features that had been acquired by the symbols. Using an ABA reversal design we then demonstrated that 1 participant classified the symbols in accordance with the contextual cues and acquired features when present, but not in the absence of the contextual cues. A 3rd participant showed symbol classification that differed from that predicted by the procedures, and the 4th classified the symbols based on one set of features but not on context. These data describe one set of conditions that could account for the establishment of complex classification repertoires that occur in natural settings.     

Associative symmetry by pigeons after few-exemplar training

The present experiment investigated whether pigeons can show associative symmetry on a two-alternative matching-to-sample procedure. The procedure consisted of a within-subject sequence of training and testing with reinforcement, and it provided (a) exemplars of symmetrical responding, and (b) all prerequisite discriminations among test samples and comparisons. After pigeons had learned two arbitrary-matching tasks (A-B and C-D), they were given a reinforced symmetry test for half of the baseline relations (B1-A1 and D1-C1). To control for the effects of reinforcement during testing, two novel, nonsymmetrical responses were concurrently reinforced using the other baseline stimuli (D2-A2 and B2-C2). Pigeons matched at chance on both types of relations, thus indicating no evidence for symmetry. These symmetrical and nonsymmetrical relations were then directly trained in order to provide exemplars of symmetry and all prerequisite discriminations for a second test. The symmetrical test relations were now B2-A2 and D2-C2 and the nonsymmetrical relations were D1-A1 and B1-C1. On this test, 1 pigeon showed clear evidence of symmetry, 2 pigeons showed weak evidence, and 1 pigeon showed no evidence. The previous training of all prerequisite discriminations among stimuli, and the within-subject control for testing with reinforcement seem to have set favorable conditions for the emergence of symmetry in nonhumans. However, the variability across subjects shows that methodological variables still remain to be controlled.     

Derived false memories using a respondent‐type (ReT) procedure

The present investigation used a respondent‐type (ReT) training procedure to generate derived false memories. A one‐to‐many ReT training procedure was implemented in order to establish two stimulus equivalence classes, each consisting of one shape and 24 random words (i.e., Class 1 and Class 2). A partial test for stimulus equivalence with a subset of stimuli from each class followed. Failing an equivalence test resulted in additional ReT training and equivalence testing on new subsets of stimuli. After passing an equivalence test, participants were presented with 12 study‐list words from Class 1 for memorization, followed by a distraction task. Finally, free recall and recognition tests for the study‐list words were implemented. False recall and false recognition were more frequent for nonstudied Class 1 words than for nonstudied Class 2 words. These derived false‐memory effects were more pronounced among those participants exhibiting more training and testing cycles and higher accuracy on stimulus equivalence tests. Furthermore, false recall and false remembering of nonstudied Class 1 words were more frequent for words that had been equivalence‐tested than for words that had not been equivalence‐tested. These results show how responses to contiguous stimuli could produce derived false memories and also highlight the role played by the equivalence test in increasing their emergence.