DISCRIMINATION OF THE SPATIAL DERIVATIVES OF HORIZONTAL BINOCULAR DISPARITY

Observers discriminated the relative disparity, disparity gradient, an d disparity curvature of surfaces defined by horizontal binocular disp arity in random-dot stereograms; In experiment 1, thresholds for discr iminating the depth of sinusoidal corrugations were very similar for d ifferent corrugation frequencies, despite large differences in dispari ty gradient and disparity curvature. Thus observers used a relative di sparity cue in preference to a slant or curvature cue. Experiment 2 is olated the spatial derivatives of disparity by jittering the other ava ilable cues, using surfaces with square-wave, triangle-wave, and parab olic-wave profiles. Weber fractions were 4%-10% for relative disparity , 6%-12% for disparity gradient, and 15%-30% for disparity curvature. Experiment 3 confirmed this result for larger surfaces. The study supp orts the view that human stereoscopic vision aims to represent the loc al scene relative to the observer, at the expense of computing intrins ic properties of objects, such as curvature. (C) 1997 Optical Society of America [S0740-3232(97)01802-4]