BINOCULAR ALIGNMENT IN DIFFERENT DEPTH PLANES

A generally accepted notion in binocular vision is that we see the wor ld as if viewed by a single eye, the cyclopean eye. A consequence of s eeing the world from a single point in space is that the outlines of o ccluding and occluded surfaces have the same shape. We designed stereo grams in which subjects aligned binocularly visible lines to each othe r. The lines were lying in different depth planes. In the vicinity of occluded areas, binocular alignment was achieved by alignment of the l ines in the eye that viewed the monocularly visible details. Stereogra ms in which shapes of surfaces lying in different depth planes were co mpared to each other show that occluding and occluded surfaces do not have the same shape: a square surface occludes rectangular surfaces in other depth planes of which the horizontal widths are smaller than th e vertical widths. This difference in perceived shape is not possible if the centre of binocular direction has a fixed position in the head. Copyright (C) 1996 Elsevier Science Ltd.