Judgment of Slant in Response to an Isolated Gradient of Stimulation

Abstract

The following hypothesis was proposed to account for the consistent slant perceptions obtained in response to a gradient of outline convergence and textural density in isolation: the gradient of textural density or outline convergence in isolation will determine a constant perception of slant if there is a high probability that the contours of the distal shape are regular and invariant. In order to examine this hypothesis judgments of the slant of four kinds of standards were obtained: NR, a textureless white rectangle slanted to one of four angles with O's line of sight; PNR, projective representations of NR presented in O's frontal-parallel plane; R, a playing card of the same dimensions and at the same angles as NR; PR. projective representations of the playing card presented in the frontal parallel plane. The judgments were made under conditions which eliminated the gradients of disparity and parallax. The main finding was that the apparent slant of NR and R varied systematically with variations of objective slant, while the apparent slant of PNR and PR varied systematically with the represented slant. However, the apparent slant of the projective standards differed significantly from that of their respective objective standards.