Conditional discrimination and equivalence relations: Control by negative stimuli.

Three college students sat at a computer. They saw two samples and two choices.

They had to pick the comparison that went with each sample. Sometimes the correct pick was the one that had never been wrong (negative-comparison control).

The team kept trials going until each person matched all possible pairs without errors.

All three adults formed new equivalence classes. The classes were built by learning what NOT to pick, not just what TO pick.

This was the first clean lab proof that “reject-control” alone can create stimulus equivalence.

Foti et al. (2015) seems to clash: they showed select-control (picking the S+) makes stronger classes and fuller transfer than reject-control. The gap is method. C et al. used ONLY negative-comparison teaching, while F et al. compared both types side-by-side and measured how well each worked.

Perez et al. (2021) moved the story forward. After classes form, simple background colors can flip the stimulus function from good to bad. That means the “do-not-pick” history shown by C et al. can later be switched on and off by context cues.

Almeida-Verdu et al. (2008) widened the field. They took the same equivalence idea and showed deaf children with cochlear implants can build auditory-visual classes, proving the effect is not limited to typical adults in a lab.

If you run equivalence-based instruction, remember that learners may be building classes from what they reject, not only from what they select. Check for reject-control when a child keeps picking the wrong card after many trials. You might need to add clear S+ teaching or extra context cues to firm up the class.