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Pigeon (Columba livia) and rat (Rattus norvegicus) performance in the midsession reversal procedure depends upon cue dimensionality.

Pigeons (Columba livia) produce many anticipatory and perseverative errors on discrimination tasks with a reversal of reward contingencies partway through the session. Prior comparative research has suggested that rats (Rattus norvegicus) do not show the same number of errors and produce results that more closely resemble those of humans. We examined pigeons' performance on a visual-spatial discrimination with the reversal point randomized within the session and found that they showed remarkably few errors. When these subjects were split into groups with the contingencies for reward unconfounded, the birds in the spatial-contingency group maintained their performance, and those in the visual-contingency group made many more anticipatory and perseverative errors. We also examined the performance of naïve pigeons on a spatial midsession reversal task and found a pattern of results similar to those shown by pigeons that had previously been trained on a visual-spatial reversal procedure. Finally, we studied rats on a T-maze using a spatial-discrimination midsession reversal task and found that the rats showed a large number of anticipatory and perseverative errors. Near-perfect performance on the midsession reversal task appears to be subject to the ability of the animal to orient spatially during the intertrial interval, rather than being due to broad species differences.