Garcia, A., & Benjumea, S. (2006).
The emergence of symmetry in a conditional discrimination task using
different responses as propioceptive samples in pigeons.
Journal of the Experimental Analysis of Behavior, 86, 65-80.
In Experiment 1, 10 pigeons were exposed to a successive symbolic
matching-to-sample procedure in which the sample was generated by the
pigeons’ own behavior. Each trial began with both response keys
illuminated white, one being the “correct” key and the othe
the “incorrect” key. The pigeons had no way of discriminating
which key was correct and which incorrect, since
these roles were assigned on a random basis with the same probability of 0.5 for
each key. A fixed ratio of five responses was required on the correct key.
However, each time the pigeon pecked the incorrect key, the correct key response
counter reset. Five consecutive pecks on the correct key was the only way to
end this component, and switch off both key lights. Two seconds later, these same
keys were illuminated again, one green and the other red (comparison stimuli).
Now, if the correct white key had been on the left, a peck at one color produced
food, and if the correct white key had been on the right, a peck at the other
color produced food. When the pigeons had learned this discrimination, they were
exposed to several symmetry tests (simultaneous presentations of both keys
illuminated the same color—i.e., both red or both green), in order to interchange
the sample with the comparison stimuli. In Experiment 2, the importance of
requiring discrimination between the samples and between the comparisons was analyzed.
In Experiment 3, we compared the results of Experiment 1 with a slightly different
experiment, which resulted in discrimination of key position, an exteroceptive stimulus.
The results showed that symmetry emerged only when different responses were used as
samples.
Key words: stimulus control, equivalence relations, symmetry, conditional
discrimination, matching-to-sample, differential response, key peck, pigeons