Binocular depth reversals despite familiarity cues.

Stereoscopic depth can be reversed by interchanging the left- and right-eye views (pseudoscopy) when abstract stereograms are used, but not when stereograms contain natural objects or scenes. This resistance to reversal of depth has traditionally been attributed to familiarity with the shape of objects and the presence of monocular depth cues. However, when texture disparity is neutralized by making the texture perspective of surfaces identical for both eyes, even a highly familiar object, like a monocularly recognizable human face, appears as concave (nose pointing inwards) when viewed pseudoscopically.