Perceived shape and its dependency on perceived slant.

Koffka's suggestions that perceived shape and perceived slant "will be coupled together so that if one changes, the other changes also" and that errors in perceived shape vary as some function of errors in perceived slant were examined. Ss described, by means of appropriate response mechanisms, the shapes and slants of trapezoids. Shape and slant responses were made both monocularly and binocularly. The changes in reported shape varied as a function of changes in reported slant. Also, shape response errors varied as a function of slant response errors under monocular viewing when Ss had no prior binocular experience with the trapezoid. The functions relating perceived shape to perceived slant were comparable to the function predicted by the Beck and Gibson shape-slant invariance hypothesis.