Symmetry and transitivity of conditional relations in monkeys (Cebus apella) and pigeons (Columba livia).
Equivalence does not emerge automatically—monkeys handle transitivity, pigeons need added supports, so check symmetry and transitivity before assuming stimulus classes.
01Research in Context
What this study did
The team taught monkeys and pigeons a simple matching game. If sample A appeared, the animal had to pick comparison B; if sample B appeared, they picked C.
After many correct trials, the researchers tested for two untaught skills. Symmetry meant picking A after seeing B. Transitivity meant picking A after seeing C. No extra rewards were given during these probe trials.
What they found
Monkeys passed the transitive test but only weakly showed symmetry. Pigeons failed both new tests.
The results show that equivalence relations do not form the same way in every species.
How this fits with other research
Saunders et al. (1988) ran the same pigeon test three years later and got the same failure. This direct replication strengthens the claim that standard matching-to-sample alone is not enough for pigeons.
Ribes-Iñesta (1999) later showed that pigeons can reach transitive-like control if you add special reinforcement for looking at the correct key. This finding extends the 1985 work by giving trainers a tool to fix the pigeon gap.
Swisher et al. (2015) uncovered another layer: pigeon symmetry vanished when probe pictures moved to new screen spots. Keep training and probe locations identical or you may lose emergent relations.
Aragona et al. (1975) once found fast hue matching in pigeons and called it equivalence. The 1985 study used stricter tests, so the earlier positive result now looks like a simpler transfer effect, not full equivalence.
Why it matters
If you work with learners who struggle with emergent relations, check for species- or learner-type limits. Use extra cues like distinctive observing responses or hold stimulus spots constant. These tweaks can turn failed probes into solid equivalence classes.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →After baseline matching is solid, run five unreinforced symmetry probes and five transitivity probes; if scores dip below 80 %, add distinctive observing responses or keep stimulus locations identical and retest.
02At a glance
03Original abstract
In Experiment 1 six monkeys were tested with discriminative relations that were backward relative to their training in a 0-second conditional ("symbolic") matching procedure. Although there was some indication of backward associations, the evidence was generally weak, and statistical evaluations did not reach conventional significance levels. Unlike children, who show backward associations to the point of symmetry, monkeys and pigeons display at best only weak and transient backward associations. In Experiment 2 associative transitivity was assessed across two sets of conditional matching tasks. All four monkeys tested demonstrated strong transitivity. In contrast, in Experiment 3 there was no evidence of transitivity in three pigeons tested under conditions closely comparable to those of Experiment 2. These results may identify some key features of interspecies differences and contribute to analyses of serial learning in animals.
Journal of the experimental analysis of behavior, 1985 · doi:10.1901/jeab.1985.44-35