title: Directional Bias in the Perception of Cast Shadows.
abstract: Previous studies have demonstrated that the perception of shading is based upon assumptions about lighting direction, for example, light from above. However, it is not clear whether these assumptions are used in the perception of cast shadows. Moreover, it is unclear whether a perceptual interaction exists between shading and cast shadows because until now they have been studied separately. In this study, we investigated through three experiments whether the light-from-above (or another direction) assumption is used in interpreting ambiguous cast shadows, and whether shading information influences the interpretation of cast shadows. Our results indicate the existence of the light-from-above assumption in interpreting cast shadows. Consistent shading information enhanced the interpretation, and judgments of lighting direction were also based on both cast shadow and shading information. However, the perceptual determination of shape from shading was relatively independent of the cast shadow interpretation or the lighting direction judgments of the scene.
authors.affiliation: Graduate School of Design, Kyushu University, Fukuoka, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Koizumi
authors.affiliation: Faculty of Design, Kyushu University, Fukuoka, Japan; Research Center for Applied Perceptual Science, Kyushu University, Fukuoka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ito
authors.affiliation: Faculty of Design, Kyushu University, Fukuoka, Japan; Research Center for Applied Perceptual Science, Kyushu University, Fukuoka, Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Sunaga
authors.affiliation: Faculty of Design, Kyushu University, Fukuoka, Japan; Research Center for Applied Perceptual Science, Kyushu University, Fukuoka, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Ogawa
keywords: cast shadow; lighting direction; shading; three-dimensional perception