title: The relationship between perceived length and egocentric location in Müller-Lyer figures with one versus two chevrons.
abstract: We examined the apparent dissociation of perceived length and perceived position with respect to the Müller-Lyer (M-L) illusion. With the traditional (two-chevron) figure, participants made accurate open-loop pointing responses at the endpoints of the shaft, despite the presence of a strong length illusion. This apparently non-Euclidean outcome replicated that of Mack, Heuer, Villardi, and Chambers (1985) and Gillam and Chambers (1985) and contradicts any theory of the M-L illusion in which mislocalization of shaft endpoints plays a role. However, when one of the chevrons was removed, a constant pointing error occurred in the predicted direction, as well as a strong length illusion. Thus, with one-chevron stimuli, perceived length and location were no longer completely dissociated. We speculated that the presence of two opposing chevrons suppresses the mislocalizing effects of a single chevron, especially for figures with relatively short shafts.
authors.affiliation: NASA Ames Research Center, Moffett Field, California 94035, USA. robert.b.welch@nasa.gov
authors.forename: Robert B
authors.initials: RB
authors.lastname: Welch
authors.forename: Robert B
authors.initials: RB
authors.lastname: Post
authors.forename: Wayland
authors.initials: W
authors.lastname: Lum
authors.forename: William
authors.initials: W
authors.lastname: Prinzmetal
mesh_terms: D000328:Adult; D001288:Attention; D004193:Discrimination Learning; D005260:Female; D006801:Humans; D008297:Male; D009903:Optical Illusions; D009949:Orientation; D010364:Pattern Recognition, Visual; D011340:Problem Solving; D011597:Psychomotor Performance; D011601:Psychophysics; D012858:Size Perception