Evidence for response membership in stimulus classes by pigeons.
Keep the response the same across stimuli in a class, and the response itself can become equivalent to those stimuli.
01Research in Context
What this study did
Tassé et al. (2013) worked with pigeons to test a bold idea. Could the birds' pecks become part of a stimulus class?
The birds learned to match colors, shapes, and dots. Each correct match earned food. The key twist: the birds had to peck the same side key for every picture in a class.
What they found
The pigeons passed symmetry and expansion tests. Their side-key pecks acted like full class members.
In plain words, the response itself became equivalent to the pictures it matched.
How this fits with other research
This result flips an earlier pigeon study on its head. van Schrojenstein Lantman-de Valk et al. (2006) saw no sign that center-key pecks entered classes. The difference: the 2006 birds used varied peck patterns, while the 2013 birds used one uniform side-key response.
Ahlborn et al. (2008) had already shown that uniform responding inside a class is needed for equivalence. The 2013 paper proves that when you meet that rule, the response can join the class.
Johnson et al. (2014) later showed adult humans can merge separate classes into bigger sets. Both studies stretch equivalence beyond simple picture sets, but in different species and ways.
Why it matters
When you teach matching tasks, watch the child's response form. If the same topography (sign, word, or switch press) is used for every item in a class, that response may become part of the class. This means you can test for emergent relations by swapping in new responses, not just new pictures. Try keeping the response uniform across stimuli you want equivalent, then probe with novel responses to see if the class holds.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Pick one target class and require the same switch press or sign for every stimulus in that class, then test if new pictures also evoke that response.
02At a glance
03Original abstract
Response membership in pigeons' stimulus-class formation was evaluated using associative symmetry and class expansion tests. In Experiment 1, pigeons learned hue-hue (AA) and form-form (BB) successive matching plus a modified hue-form (AB) task in which reinforcement was contingent upon a left versus right side-key response after the positive AB sequences. On subsequent BA (symmetry) probe trials, pigeons responded more often to the comparisons on the reverse of the positive than negative AB sequences and, more importantly, preferentially pecked the side key consistent with symmetry after the reversed positive sequences. In Experiment 2, the original three baseline tasks were supplemented by dot-white (CC) successive matching in which reinforcement was contingent upon a left versus right side-key response after the positive CC sequences. Class expansion was then tested by presenting nonreinforced CA and CB successive matching probes. Comparison response rates were mostly nondifferential on CA probes but were uniformly higher on CB probes that consisted of the C samples and B comparisons from the same, hypothesized class. Together, these results provide evidence that responses can become members of stimulus classes, as predicted by Urcuioli's (2008) theory of pigeons' stimulus-class formation and Sidman's (2000) theory of equivalence.
Journal of the experimental analysis of behavior, 2013 · doi:10.1002/jeab.17