An instance of spurious equivalence relations.
Kids can form 'equivalence' links that were never taught—probe with control stimuli and tighten your MTS design.
01Research in Context
What this study did
White et al. (1990) ran a matching-to-sample lesson with kids. They wanted to see if true equivalence classes would form.
The children learned A-B and B-C matches. Later probes checked if they picked the untaught A-C and C-A links.
What they found
Most kids showed the expected A-C and C-A choices. But two children also 'matched' control pictures that were never paired with anything.
The extra links looked like equivalence, yet the teaching had never given a basis for them. The authors called the outcome 'spurious equivalence'.
How this fits with other research
Plazas et al. (2025) now shows how to avoid the problem. They trained both select and reject relations in the same lesson—called detached MTS. Their design produced clean equivalence without the false positives G et al. warned about.
Taylor et al. (1993) adds another wrinkle. They showed that the pictures a child does NOT pick can still gain control. Together with G et al., this tells us that unnoticed cues—either in the rejects or in the room—can sneak into the class.
Fabbretti et al. (1997) kept the basic method but used it to teach equivalence-of-equivalence, a step toward analogical reasoning. Because they used tighter stimulus control, they saw no spurious links, confirming that the artifact is preventable.
Why it matters
Before you say a client has 'mastered equivalence,' run extra probes with brand-new control stimuli. If the learner picks those too, re-check your pictures, screen colors, and even the position of the cards. Add reject-trial training or rotate your foils so that only the taught relations can guide the choices. A two-minute probe can save you from building an entire program on fake classes.
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02At a glance
03Original abstract
Four normal children learned conditional discriminations that had upper-case or lower-case Greek letters as comparison stimuli, and dictated letter names as samples. Experimental stimuli were three pairs of letters; within each pair, an upper- and a lower-case letter were conditionally related to the same dictated sample. Four control stimuli, also upper- and lower-case letters, were each conditionally related to a different dictated sample. Conditional-discrimination tests for equivalence used the upper- and lower-case letters both as samples and comparisons. Untaught conditional relations between the upper- and lower-case members of each experimental stimulus pair were expected to emerge on the basis of their previously established relations to a common sample. The emergence of conditional relations between control stimuli, however, would have suggested an artifact. In test trials with the experimental stimuli as samples and comparisons, new conditional discriminations emerged as expected with all four children. With two of the children, however, consistent discriminations also emerged between control stimuli. Evidence suggested that uncontrolled features of the program for teaching the children the baseline conditional discriminations might have been responsible for the emergence of untaught conditional relations.
The Analysis of verbal behavior, 1990 · doi:10.1007/BF03392842