The Aperture Problems in the Pulfrich Effect

Abstract

The Pulfrich effect yields a perceived depth for horizontally moving objects but not for vertically moving ones. In this study the Pulfrich effect was measured by translating oblique lines seen through a circular window, which made motion direction ambiguous. Overlaying random dots that moved horizontally, vertically, or diagonally controlled the perceptual motion direction of the lines. In experiment 1, when the lines were seen to move horizontally, the effect was strongest in spite of the same physical motion of the lines. Experiment 2 was performed to test the above conditions again, excluding the Pulfrich effect of the dots on the depth of the lines. The overlaid dots were presented to one eye only. The result showed that the Pulfrich effect of the lines was persistently strong in spite of the perceptual changes in motion direction. Experiment 3 also showed that the Pulfrich depth was independent of the perceived horizontal speed in a plaid display. The Pulfrich effect was determined by measuring the horizontal disparity component, independently of the perceived motion direction. These results demonstrate that the aperture problems in motion and stereopsis in the Pulfrich effect are solved independently.

On the Aperture Problem of Binocular 3D Motion Perception

“…In many studies researchers have addressed the aperture problem of 2D motion perception [7,[10][11][12][13] but surprisingly few have investigated the equally pertinent aperture problem of 3D motion perception [14]. In these studies researchers have employed lines or plaids moving at a constant depth behind an aperture [15,16] or random-dots on a surface moving in depth along the line of sight [17,18]. Here we investigate the perceived 3D motion direction of a single line stimulus moving behind a circular aperture on a horizontal or oblique trajectory in depth.…”