title: Perception of physical stability and center of mass of 3-D objects.
abstract: Humans can judge from vision alone whether an object is physically stable or not. Such judgments allow observers to predict the physical behavior of objects, and hence to guide their motor actions. We investigated the visual estimation of physical stability of 3-D objects (shown in stereoscopically viewed rendered scenes) and how it relates to visual estimates of their center of mass (COM). In Experiment 1, observers viewed an object near the edge of a table and adjusted its tilt to the perceived critical angle, i.e., the tilt angle at which the object was seen as equally likely to fall or return to its upright stable position. In Experiment 2, observers visually localized the COM of the same set of objects. In both experiments, observers' settings were compared to physical predictions based on the objects' geometry. In both tasks, deviations from physical predictions were, on average, relatively small. More detailed analyses of individual observers' settings in the two tasks, however, revealed mutual inconsistencies between observers' critical-angle and COM settings. The results suggest that observers did not use their COM estimates in a physically correct manner when making visual judgments of physical stability.
authors.affiliation: Department of Psychology and Center for Cognitive Science, Rutgers University, New Brunswick, NJ, USA.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Cholewiak
authors.affiliation: Department of Psychology, Justus-Liebig-University Giessen, Giessen, Germany.
authors.forename: Roland W
authors.initials: RW
authors.lastname: Fleming
authors.affiliation: Department of Psychology and Center for Cognitive Science, Rutgers University, New Brunswick, NJ, USA.
authors.forename: Manish
authors.initials: M
authors.lastname: Singh
mesh_terms: D003867:Depth Perception / Q000502:physiology*; D005556:Form Perception / Q000502:physiology*; D006112:Gravitation; D006801:Humans; D021621:Imaging, Three-Dimensional
keywords: 3-D shape; center of mass; critical angle; perceived object stability