Judgment of Slant with Constant Outline Convergence and Variable Surface Texture Gradient

Abstract

Twenty-four Os estimated the slants of rectangles and trapezia, using monocular vision with fixed head under reduced viewing conditions. The trapezia were the frontal-parallel projections of the rectangles at 45° slant. The rectangles, one untextured and three textured, were presented in the frontal-parallel plane and at 15°, 30°, 45°, and 60° slant. The trapezia, one untextured and three textured, were presented only in the frontal-parallel plane. For the rectangles at 45° and the trapezia, the six textured forms presented four variations in texture density gradient produced by photographing a uniform but random texture of solid circles in the frontal-parallel plane and at 45° slant. The estimated slants for the rectangles at 45° slant and the trapezia at 0° slant were generally equivalent, differences in texture notwithstanding. Outline convergence was almost exclusively the effective cue for slant and texture was generally ineffective.