title: Pigeons do not perceptually complete partly occluded photos of food: an ecological approach to the "pigeon problem".
abstract: Humans routinely complete partly occluded objects to recognize the whole objects. However, a number of studies using geometrical figures and even conspecific images have shown that pigeons fail to do so. In the present study, we tested whether pigeons complete partially occluded objects in a situation simulating a natural feeding context. In Experiment 1, we trained pigeons to peck at any photograph of food and not to peck at any containing a non-food object. At test, we presented both photos of food partly occluded by pigeon's feather and photos simply truncated at the same part. We predicted that if the pigeons perceptually completed the occluded portion, then they would discriminate the photos of occluded food better than the truncated photos. The result was that the pigeons pecked at the truncated photos earlier than the occluded photos. Placing the occluder next to all of the stimuli in Experiment 2 or substituting indented lozenge for the feather in Experiment 3 did not affect the results. Thus, even in a simulated ecologically significant situation, pigeons continued to not show evidence of perceptual completion.
authors.affiliation: Department of Psychology, Graduate School of Letters, Kyoto University, Yoshida-Honmachi, Sakyo, Kyoto 606-8501, Japan. ushitani@psy.bun.kyoto-u.ac.jp
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Ushitani
authors.forename: Kazuo
authors.initials: K
authors.lastname: Fujita
mesh_terms: D000818:Animals; D001070:Appetitive Behavior; D001288:Attention; D010856:Columbidae; D003216:Conditioning, Operant; D004193:Discrimination Learning; D005260:Female; D008297:Male; D010364:Pattern Recognition, Visual; D010466:Perceptual Closure; D010470:Perceptual Masking