title: Horizontal-vertical illusion: continuous decrement or the deviant first guess?
abstract: Numerous studies have reported that repetitive or extensive inspection leads to short-term decrement of the horizontal-vertical illusion. The present experiment explored whether this decrement reflects a gradual decline, as previously assumed, or is better described as a singular drop-off beyond the initial evaluation. 111 student participants adjusted vertical or horizontal lines such that they appeared equally long with a perpendicular standard. There were 8 successive adjustment trials for each subject. The results suggest that a substantial component of the illusion depends on the first impression assessment. The earlier anatomical and cognitive theories of the horizontal-vertical illusion cannot incorporate this datum. However, recent findings suggest that a motor theory of illusion might accommodate the observed one-step decrement in the illusion.
authors.affiliation: Department of Psychology, Umeå University, Sweden. jaanus.raudsepp@psy.umu.se
authors.forename: Jaanus
authors.initials: J
authors.lastname: Raudsepp
mesh_terms: D000328:Adult; D001288:Attention; D004193:Discrimination Learning; D004215:Distance Perception; D005260:Female; D006801:Humans; D008297:Male; D009903:Optical Illusions; D009949:Orientation; D010364:Pattern Recognition, Visual; D011597:Psychomotor Performance; D011601:Psychophysics