title: Perception of the standard and the reversed Müller-Lyer figures in pigeons (Columba livia) and humans (Homo sapiens).
abstract: The authors compared perception of the standard and reversed Müller-Lyer figures between pigeons (Columbia livia) and humans (Homo sapiens). In Experiment 1, pigeons learned to classify 6 lengths of target lines into "long" and "short" categories by pecking 2 keys on the monitor, ignoring the 2 brackets so placed that they would not induce an illusion. In the test that followed, all 3 birds chose the "long" key more frequently for the standard Müller-Lyer figures with inward-pointing brackets (><) than for the figures with outward-pointing brackets (<>). The subjects' responses were accountable by neither overall lengths of the figures nor horizontal gaps between the 2 brackets. For the reversed figures, effects of the brackets were absent. These results suggested that the pigeons perceived the standard Müller-Lyer illusion but not the reversed one. Experiment 2 confirmed that humans perceived both types of the illusion. Pigeons and humans may perceive the same illusory figures in different ways.
authors.affiliation: Department of Psychology, Graduate School of Letters, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan. NNakamura@LPs.mbox.media.kyoto-u.ac.jp
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nakamura
authors.forename: Kazuo
authors.initials: K
authors.lastname: Fujita
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Ushitani
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Miyata
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001288:Attention; D002648:Child; D002755:Choice Behavior; D010856:Columbidae; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009903:Optical Illusions; D009949:Orientation; D010364:Pattern Recognition, Visual; D011601:Psychophysics; D012055:Reinforcement Schedule; D012193:Reversal Learning; D012858:Size Perception; D013045:Species Specificity