title: The limits of shape constancy: point-to-point mapping of perspective projections of flat figures
abstract: The present experiments investigate point-to-point mapping of perspective transformations of 2D outline figures under diverse viewing conditions: binocular free viewing, monocular perspective with 2D cues masked by an optic tunnel, and stereoptic viewing through an optic tunnel. The first experiment involved upright figures, and served to determine baseline point-to-point mapping accuracy, which was found to be very good. Three shapes were used: square, circle and irregularly round. The main experiment, with slanted figures, involved only two shapes-square and irregularly shaped-showed at several slant degrees. Despite the accumulated evidence for shape constancy when the outline of perspective projections is considered, metric perception of the inner structure of such projections was quite limited. Systematic distortions were found, especially with more extreme slants, and attributed to the joint effect of several factors: anchors, 3D information, and slant underestimation. Contradictory flatness cues did not detract from performance, while stereoptic information improved it
keyphrases: shape constancy point-to-point mapping experiments 2D outline figures diverse viewing conditions binocular free viewing monocular perspective 2D cues optic tunnel stereoptic viewing anchors 3D information slant underestimation flat figure perspective projections 3D shape perception human factors 3D information displays