Object-picture equivalence in the pigeon: An analysis with natural concept and pseudoconcept discriminations.

Pigeons were trained on a natural concept (food vs. non-food) and on a pseudoconcept (arbitrary classification of edible and not edible stimuli). The birds were trained with real objects and then tested with colour photographs in the object-to-picture transfer group, and they were trained and tested in the reverse order in a picture-to-object transfer group. The subjects showed good transfer of discrimination in both directions when the task involved a natural concept, but they did not show transfer of a pseudoconcept discrimination. Because all birds saw the same stimuli during the discriminative training, the difference in transfer was due to the type of classification of the stimuli. These results suggest object-picture equivalence based on functional classification.