Abstract
Casual observation suggests that pigeons and other animals can recognize occluded objects; yet, laboratory research has thus far failed to show that pigeons can recognize occluded objects. In a series of experiments with shaded, textured stimuli, we investigated pigeons' ability to recognize occluded objects. After first teaching pigeons to recognize four unoccluded objects, Experiment 1 found that pigeons failed to recognize those objects when they were partially occluded by another surface (a brick wall); pigeons also failed to recognize the intact objects when they were placed on top of the occluding surface. These results prompted Experiment 2, in which the same pigeons that served in Experiment 1 were now required to discriminate objects that were placed on top of the occluder. Following this training with the unoccluded stimuli and with the stimuli placed on top of the occluder, the pigeons' recognition of occluded objects dramatically improved. The final part of Experiment 2 found that the pigeons' newly acquired ability to recognize occluded objects was not limited to the trained objects, but [ADD: generalized] to novel objects as well. Evidently, the recognition of occluded objects requires pigeons to learn to discriminate the object from the occluder; once this discrimination is mastered, partially occluded objects can be readily recognized.