The relation of apparent shape to apparent slant in the perception of objects.

Abstract

The relationship of apparent shape and apparent slant to the perception of the shape of objects in space was studied in 3 experiments. It was demonstrated in Expt. I that a reduced retinal shape without stimulation for the slant of the surface can induce a whole family of apparent shapes and does not necessarily determine the perpendicular cross-sectional member of the family. But there was a strong "presumption" for the frontal shape and, in the quadrilateral family, this won out over the tendency to see a rectangle. As to the linkage between shape and slant within the family of shape-slants, it proved to be by no means perfect. Expt. II showed that, again for a reduced retinal shape, an illusory slant can induce an illusory shape. The phenomenal slant of such an object will tend to be that of the textured background surface whatever its physical slant may be. Expt. II yielded no exceptions to the linkage hypothesis, but it did not constitute as strict a test. The strictness of the linkage seemed to depend on the kind of shape seen and on the direction of its slant. The linkage may be learned, but a probabilistic theory of the percepts attained does not readily explain the facts. Expt. III showed that constancy of the perceptions of shape appeared when stimulation for slant was provided, but not universally.