Effects of a meaningful, a discriminative, and a meaningless stimulus on equivalence class formation.
Adding one meaningful or familiar stimulus to an equivalence class triples college students’ learning success.
01Research in Context
What this study did
Fields et al. (2012) asked 30 college students to learn three-stimulus equivalence classes. Each class had two abstract shapes and one special item. The special item was either a meaningful picture, a shape that had been used in earlier tasks, or just another random shape.
The team used a simultaneous protocol. All three pictures appeared on a screen. Students picked the one that matched the sample. After training, probes tested if the students treated all items in a class as the same.
What they found
Classes that held a meaningful picture or a familiar shape were learned by about a large share of students. Classes made of only abstract shapes were learned by only a large share.
One meaningful or familiar stimulus was enough to triple success rates.
How this fits with other research
Weissman-Fogel et al. (2015) ran the same lab setup. They showed that giving an abstract shape five prior conditional relations lifted success to the same a large share level. Meaning and training history can swap places.
Ayres‐Pereira et al. (2025) pushed the method further. When the items looked almost identical, placing the comparisons side-by-side during training let every adult succeed. Together these papers show that both stimulus meaning and arrangement matter.
Aman et al. (2002) used mild shock pairings to give neutral stimuli a history. Later tests showed full transfer of function, echoing Lanny’s point: prior function, however it is gained, greases the wheels for new equivalence relations.
Why it matters
When you build stimulus classes for language, reading, or social-skills programs, slip in at least one item the learner already knows or has worked with. A photo of mom, a favorite toy, or a previously mastered sight word can turn a hard task into an easy win. If every item must be new, give the learner a quick history with one of them first—five easy conditional-discrimination trials can be enough.
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02At a glance
03Original abstract
Thirty college students attempted to form three 3-node 5-member equivalence classes under the simultaneous protocol. After concurrent training of AB, BC, CD, and DE relations, all probes used to assess the emergence of symmetrical, transitive, and equivalence relations were presented for two test blocks. When the A-E stimuli were all abstract shapes, none of 10 participants formed classes. When the A, B, D, and E stimuli were abstract shapes and the C stimuli were meaningful pictures, 8 of 10 participants formed classes. This high yield may reflect the expansion of existing classes that consist of the associates of the meaningful stimuli, rather than the formation of the ABCDE classes, per se. When the A-E stimuli were abstract shapes and the C stimuli became S(D)s prior to class formation, 5 out of 10 participants formed classes. Thus, the discriminative functions served by the meaningful stimuli can account for some of the enhancement of class formation produced by the inclusion of a meaningful stimulus as a class member. A sorting task, which provided a secondary measure of class formation, indicated the formation of all three classes when the emergent relations probes indicated the same outcome. In contrast, the sorting test indicated "partial" class formation when the emergent relations test indicated no class formation. Finally, the effects of nodal distance on the relatedness of stimuli in the equivalence classes were not influenced by the functions served by the C stimuli in the equivalence classes.
Journal of the experimental analysis of behavior, 2012 · doi:10.1901/jeab.2012.97-163