Relational discrimination by pigeons in a go/no-go procedure with compound stimuli: a methodological note.
Pigeons can do symmetry but not equivalence under go/no-go compound training, so do not assume cross-species generality.
01Research in Context
What this study did
Campos et al. (2011) taught pigeons to peck a key when two pictures appeared together. The birds first learned A-B and A-C pairs in a go/no-go setup.
Next the team tested if the birds would treat B-A, C-A, B-C and C-B as the same without extra training. They wanted to see full equivalence emerge.
What they found
The pigeons passed the backward, or symmetry, tests: B-A and C-A. They treated the reversed pairs like the trained ones.
They failed the mixed, or transitivity, tests: B-C and C-B. Full equivalence did not show up, even though symmetry did.
How this fits with other research
Navarro et al. (2025) show the opposite pattern in humans. People gave strong symmetry and full equivalence even when the authors removed training tricks that usually help.
The gap fits Lionello-DeNolf (2021), a review that found only about 30 % of non-human subjects ever show symmetry. The review lists the pigeon data as one more piece of that ceiling.
Lydersen et al. (1974) also used compound cues with pigeons and saw better accuracy, but they never tested equivalence. Together the studies warn that adding more stimuli helps simple discrimination, yet equivalence still stalls in birds.
Why it matters
If you build equivalence curricula for humans, do not bank on animal data alone. The pigeon work says symmetry can pop up, but the harder relations may not follow. Test each relation in your learner, especially transitivity, before you call the set equivalent. And if you run intra-verbal programs, keep the species in mind: birds may need qualitatively different teaching steps.
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02At a glance
03Original abstract
A go/no-go procedure with compound stimuli typically establishes emergent behavior that parallels in structure and typical outcome that of conventional tests for symmetric, transitive, and equivalence relations in normally capable adults. The present study employed a go/no-go compound stimulus procedure with pigeons. During training, pecks to two-component compounds A1B1, A2B2, B1C1, and B2C2 were followed by food. Pecks to compounds A1B2, A2B1, B1C2, and B2C1 re-started the 30-s stimulus presentation interval. The absence of pecking to those compounds for 30 s ended the trial. Subsequent tests presented these components in new spatial arrangements and/or in recombinative compounds that together corresponded to conventional tests of symmetry, transitivity, and equivalence: B1A1, B2A2, C1B1, C2B2, A1C1, A2C2, C1A1, C2A2 vs. B1A2, B2A1, C1B2, C2B1, A1C2, A2C1, C1A2, C2A1 (positive vs. negative instances of symmetric, transitive, and equivalence relations). On tests for symmetric relations, all pigeons behaved in a manner consistent with training on both positive instances (i.e., by responding) and on negative instances (i.e., by not responding). By contrast, the pigeons' behavior on tests for transitivity and equivalence was inconsistent with baseline training, thus failing to show the recombinative discrimination performance that is typical of normally capable humans when trained and tested using the go/no-go procedure with compound stimuli.
Journal of the experimental analysis of behavior, 2011 · doi:10.1901/jeab.2011.96-413