Emergent identity matching after successive matching training. II: Reflexivity or transitivity.
Emergent identity matching in pigeons seems to be a simple bias, not real stimulus equivalence, so probe carefully with clients.
01Research in Context
What this study did
The team worked with pigeons in three small experiments.
They first taught the birds to peck a sample shape, then a different shape.
Next they tested if the birds would peck the same shape again without extra training.
These probes were meant to show reflexivity and transitivity, two parts of stimulus equivalence.
What they found
The pigeons often picked the matching shape, but not for the right reason.
Their choices looked more like a built-in bias for sameness than true derived relations.
In short, the birds passed the test without understanding the concept.
How this fits with other research
Rasing et al. (1992) got a clear win when adults with brain injury learned name-face matching through the same equivalence steps.
The birds failed where humans succeeded, so the method extends to people but not to pigeons.
Sanders et al. (1989) saw monkeys also struggle with matching rules, backing the idea that non-human results can be weak.
Burack et al. (2004) from the same lab had already argued that matching in pigeons is learned piece by piece, not as a concept; the new data fit that story.
Why it matters
When a client quickly passes identity probes, do not assume full equivalence has formed.
Check for true concept learning by mixing in new stimuli and untrained relations.
If the learner keeps passing only the old matches, add more varied examples and test again.
This guards against calling a bias a breakthrough.
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02At a glance
03Original abstract
Three experiments evaluated whether the apparent reflexivity effect reported by Sweeney and Urcuioli (2010) for pigeons might, in fact, be transitivity. In Experiment 1, pigeons learned symmetrically reinforced hue-form (A-B) and form-hue (B-A) successive matching. Those also trained on form-form (B-B) matching responded more to hue comparisons that matched their preceding samples on subsequent hue-hue (A-A) probe trials. By contrast, most pigeons trained on just A-B and B-A matching did not show this effect; but some did--a finding consistent with transitivity. Experiment 2 showed that the latter pigeons also responded more to form comparisons that matched their preceding samples on form-form (B-B) probe trials. Experiment 3 tested the prediction that hue-hue matching versus hue-hue oddity, respectively, should emerge after symmetrically versus asymmetrically reinforced arbitrary matching relations if those relations are truly transitive. For the few pigeons showing an emergent effect, comparison response rates were higher when a probe-trial comparison matched its preceding sample independently of the baseline contingencies. These results indicate neither a reflexivity nor a transitivity effect but, rather, a possible identity bias.
Journal of the experimental analysis of behavior, 2012 · doi:10.1901/jeab.2012.97-5