Generalized identity in a successive matching‐to‐sample procedure in rats: Effects of number of exemplars and a masking stimulus
Four training examples are enough to create generalized identity matching that survives new stimuli and added noise.
01Research in Context
What this study did
Galizio and colleagues worked with eight rats. They used a matching-to-sample task with smells.
Each rat first sniffed a sample odor. Then two new smells appeared. The rat had to pick the one that matched the sample.
Training used four different smells. Later the team added a masking scent to see if the skill would hold.
What they found
After training, every rat picked the matching odor far above chance on brand-new smells.
Even when a masking smell tried to confuse them, the rats still matched correctly.
Four training examples were enough to create a generalized identity-matching skill.
How this fits with other research
Sigurðardóttir et al. (2012) showed the same pattern in adult humans. After learning Icelandic noun classes, people instantly used the rules on plural words they had never seen.
Melchiori (2000) found the same with kids learning to read. Once children formed equivalence classes with printed syllables, they could recombine them to read new words.
Baron et al. (1968) warned that matching skills fade if the learner is not forced to look—or in this case, sniff—carefully. Galizio’s rats had to sample each odor in turn, so the skill stayed strong.
Why it matters
You can build flexible identity matching with only four examples. The skill transfers even when extra noise is added. When you run equivalence training, require the learner to actively observe each sample. This keeps accuracy high and helps the skill survive real-world distractions.
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02At a glance
03Original abstract
Two experiments examined the emergence of generalized identity matching in rats using a successive discrimination procedure with olfactory stimuli. Trials consisted of the presentation of two odors separated by a 1-s interstimulus interval. Responses during the second odor presentation were reinforced only if the two odors were identical. In Experiment 1, rats were trained with two odors and then exposed to sessions that included unreinforced probe trials with novel odors. There was evidence of higher response rates on matching probe trials in some rats, but matching did not approach baseline levels. Additional training with four exemplars produced transfer to novel odors that was equivalent to baseline levels. Experiment 2 tested the possibility that detection of stimulus change, rather than generalized identity, was responsible for the transfer seen in Experiment 1. Thus, a masking odor was inserted during the 1-s interstimulus interval so that stimulus change occurred on all trials. Although response rates on probe trials were lower than baseline rates, above chance transfer to novel stimuli was still observed in four of the five animals tested. These findings support the hypothesis that transfer of matching to novel odors in this successive matching-to-sample paradigm is based on a generalized identity relation.
Journal of the Experimental Analysis of Behavior, 2018 · doi:10.1002/jeab.483