Academic journal article The Psychological Record

A Simpler Route to Stimulus Equivalence? A Replication and Further Exploration of a "Simple Discrimination Training Procedure" Canovas, Debert and Pilgrim 2014)

Academic journal article The Psychological Record

A Simpler Route to Stimulus Equivalence? A Replication and Further Exploration of a "Simple Discrimination Training Procedure" Canovas, Debert and Pilgrim 2014)

Article excerpt

The formation of stimulus equivalence classes (Sidman 2000) has been demonstrated following a variety of training procedures. Prototypical are variants of the so-called matching-to-sample (MTS) procedure, where trained relations are established between stimuli in pairs by having one stimulus, the sample, followed by a choice of other stimuli, the comparisons, one of which the participant is taught to choose consistently. A variant of MTS is the single comparison, alternative response procedure, or "Go/No Go" procedure, in which the comparison may be correct or incorrect, and the participant is reinforced for indicating one or the other. A third procedure is respondent-type training in which each sample is followed by its correct comparison in unreinforced pairings, though the demonstration of the resultant emergent equivalence relations requires an MTS test procedure. To what extent are the behavioural manifestations of stimulus equivalence (Sidman and Tailby 1982) indifferent to such varied methods by means of which they may be engendered? Also the yield of these procedures--the proportion of participants thus trained who form stimulus equivalence classes--is often less than all. Can any simpler ways be found that at least as reliably have the same outcome?

Canovas, Debert and Pilgrim (2014) reported two experiments in which functional equivalence classes were established by two different procedures that they described as "simple discrimination training". The first experiment used repeated reversal learning, in which in one reversal each stimulus in one group of three (A1, B1, and C1) served as S+ for a given response, and those in the other group (A2, B2, and C2) as S-, with these roles being swapped in the next reversal. In due course, the appropriate switch in discriminative control was acquired by all the stimuli as soon as just one stimulus had changed its role at the beginning of a new reversal. The second experiment, of which the present paper is a replication and extension, trained participants to respond on one key to any stimulus from A1, B1, and C1, and on another key for any stimulus from A2, B2, and C2. When this had been established, new key responses were trained to A1 and A2 only, and then unreinforced test trials demonstrated transfer-of-function to B1 and C1, and B2 and C2. In both experiments, all participants were therefore deemed to have formed two functional equivalence classes. Tests were then conducted for emergent conditional relations between the stimuli using a Go/No-Go procedure with compound stimuli, either within-class or between-class pairs, respectively. Three out of the four participants in Experiment 1 and all four in Experiment 2 generated emergent stimulus relations taken to indicate equivalence class formation.

However, in Experiment 1, performance on these compound tests, as the authors make clear, "... could have been based on directly reinforced sequences or conditional discriminations during the repeated reversal training." (op. cit. p. 6). This was deemed not to apply to the "simple discrimination training procedure" in Experiment 2 [seemingly a three-term discrimination, rather than the four-term conditional discrimination in "matching-to-sample" (MTS) procedures].

The straightforwardness and effectiveness of the three stages of this second experiment--initial discrimination training, rapid transfer of this training to new key responses, and the near perfect performances on the compound test of equivalence relations--seemed to offer a simpler way of establishing stimulus equivalence classes, perhaps more adaptable to younger human participants, and even non-human species, as the authors imply in their conclusions. To explore this procedure further, and relate it to more conventional procedures, the first requirement was to attempt a replication with closely similar methods. A similar set of shape stimuli was therefore assembled, and the author's program used in previous studies was adapted to the discrimination, generalization, and compound Go/No-Go programs closely similar to those used by Canovas et al. …

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