title: The visual perception of length along intrinsically curved surfaces.
abstract: The ability of observers to perceive three-dimensional (3-D) distances or lengths along intrinsically curved surfaces was investigated in three experiments. Three physically curved surfaces were used: convex and/or concave hemispheres (Experiments 1 and 3) and a hyperbolic paraboloid (Experiment 2). The first two experiments employed a visual length-matching task, but in the final experiment the observers estimated the surface lengths motorically by varying the separation between their two index fingers. In general, the observers' judgments of surface length in both tasks (perceptual vs. motoric matching) were very precise but were not necessarily accurate. Large individual differences (overestimation, underestimation, etc.) in the perception of length occurred. There were also significant effects of viewing distance, type of surface, and orientation of the spatial intervals on the observers' judgments of surface length. The individual differences and failures of perceptual constancy that were obtained indicate that there is no single relationship between physical and perceived distances on 3-D surfaces that is consistent across observers.
authors.affiliation: Department of Psychology, Western Kentucky University, Bowling Green, Kentucky 42101, USA. farley.norman@wku.edu
authors.forename: J Farley
authors.initials: JF
authors.lastname: Norman
authors.forename: Hideko F
authors.initials: HF
authors.lastname: Norman
authors.forename: Young-Lim
authors.initials: YL
authors.lastname: Lee
authors.forename: DaSha
authors.initials: D
authors.lastname: Stockton
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Lappin
mesh_terms: D003867:Depth Perception; D004193:Discrimination Learning; D004215:Distance Perception; D005556:Form Perception; D006801:Humans; D007206:Individuality; D007600:Judgment; D016011:Normal Distribution; D009903:Optical Illusions; D009949:Orientation; D010469:Perceptual Distortion; D011601:Psychophysics; D013499:Surface Properties; D014110:Touch