A Visual Spatial Aftereffect of Surface Slant

Abstract

The long (binocular) inducing period required by Bergman and Gibson to generate a measurable slant aftereffect was not necessary for a highcontrast surface. The aftereffect for the black-on-white lattice pattern dissipated exponentially. The complex surface, however, produced concomitant interfering effects, possibly decreasing the precision of aftereffect measures. A simpler surface, of vertical contours, sufficed for relatively accurate binocular (but not monocular) adjustments to the vertical. This pattern also produced interfering effects, possibly accounting for the correlation of aftereffect variance with inducing-figure slant. The five studies suggest using a single vertical contour as both inducing and test figures to study a hypothesized relationship between tilt aftereffect and slant aftereffect. A sensory spatial aftereffect occurs when the judgment of some spatial property of a test stimulus is modified as a result of prolonged stimulation by an inducing stimulus. The aftereffect is assumed to be a simple additive component and is defined as the algebraic difference between a prestimulation judgment (pretest) and a poststimulation judgment of the test stimulus (posttest).' Spatial aftereffects in the third dimension of visual space were first demonstrated by KShler and Emery.2 They reported, for example, that a frontal-parallel cardboard strip was judged to be slanted in one direction following fixation of a similar strip slanted in the opposite direction. Later, Bergman and Gibson reported the occurrence of a slant aftereffect induced by an irregularly textured burlap surface with its edges obscured from view.3 The mean afterReceived for publication by Professor E. B. Newman, August, 1967. The research was part of a thesis awarded the M.A. at the University of Sydney, 1968. The author wishes to thank Professor R. H. Day for his assistance throughout the project. 1 J. J. Gibson, Adaptation after-effect and contrast in the perception of curved lines, J. exp. Psychol., 16, 1933, 1-31; W. Kbhler and H. Wallach, Figural aftereffects: An investigation of visual processes, Proc. Amer. phil. Soc., 96, 1944, 269-357. Later investigations have usually not departed from this convention. 2 W. Kdhler and D. A. Emery, Figural after-effects in the third dimension of visual space, this JOURNAL, 60, 1947, 159-201. 3 R. Bergman and J. J. Gibson, The negative after-effect of a surface slanted in the third dimension, this JOURNAL, 72, 1959, 364-374.