Abstract
‘Stereopsis’ refers to the vivid impression of solid form and immersive space obtained under binocular viewing of real scenes. Evidence suggests that this perceptual phenomenon is not simply a product of binocular mechanisms. Visual characteristics associated with stereopsis are reliably reported by naïve observers under monocular-aperture viewing of pictorial images (Vishwanath & Hibbard, 2010). One explanation for this effect is the difference in depth-cue coherence between binocular and monocular-aperture viewing of pictures. In the former, disparity and vergence cues conflict with pictorial depth, while in the latter, these conflicting cues are eliminated, putatively causing the impression of stereopsis and a greater perception of depth relief (e.g., Ames, 1925; Michotte, 1948). Results: Subjects rated depth impression in photographs of real scenes for different cue-conflict conditions. Surprisingly, removal of conflicting binocular cues alone had the smallest effect on depth impression, while large effects were reported between conditions where there was no change in conflicting binocular cues. Subjects also judged magnitude of curvature-in-depth for images of random-textured elliptically curved surfaces. Again, contrary to the cue-conflict account, there was no effect of viewing condition (Binocular-vs.-Monocular-Aperture) on perceived curvature despite significant main effects of underlying curvature and tilt. Importantly, variance of curvature settings was lower for Monocular-Aperture viewing. Furthermore, we find that the impression of stereopsis can be elicited by solely manipulating distance cues (depth-of-field blur and focus distance) without explicit changes to depth-cue conflict. Congenital strabismics also report an impression of stereopsis under monocular-aperture viewing. These results are inconsistent with the standard view that the impression of stereopsis is a by-product of binocular vision or retinal parallax, or, that it is simply associated with changes in the magnitude of perceived of depth relief resulting from changes in depth cue coherence/conflict. The results are, however, consistent with the theory that stereopsis is a perceptual attribute related to the reliability of visual estimates of scaled (absolute) depth.
Meeting abstract presented at VSS 2012