Cite as:
Cook N D, Leumann L, Brugger P, 2003, "The reverse-perspective illusion is not caused by binocular disparity" Perception 32 ECVP Abstract Supplement

The reverse-perspective illusion is not caused by binocular disparity

N D Cook, L Leumann, P  Brugger

Reverse perspective (RP) is an illusion of movement in a static 3-D picture. The effect is seen most strikingly in the artwork of Patrick Hughes and the related 'hollow-mask illusion', and is produced by contradictory (bottom - up versus top - down) information concerning the depth of the objects in the scene. Unlike most other visual illusions, the RP illusion is not experienced simply as 'cognitive dissonance' between the contradictory information-processing, but instead leads to the projection of the contradiction onto the external object itself, such that the object takes on unreal, 'magical' movement of its own. Experiments with prism goggles (Cook et al, 2002 Perception 31 1147 - 1151) indicated that this contradiction is the cause of the illusion because the illusion disappears during head movement in the direction for which prism goggles reverse the visual field (left/right or up/down), while leaving the illusion intact in the direction unaffected by the goggles (up/down or left/right). In order to eliminate the possibility that binocular disparity plays a role in the illusion, we have built a new type of goggles (using both prisms and mirrors) that do not reverse the visual field, but do reverse the binocular disparity. In an experiment with the goggles, all twenty-five subjects judged the more distant of two objects as nearer (for most of the seven stimuli), thus demonstrating that binocular disparity was a key factor in judging distance (at ~ 40 cm). In contrast, when viewing (at ~ 40 cm) 3-D objects built in RP or normal perspective, the illusion was consistently experienced with the RP object and not experienced with the normal perspective object with or without the goggles, thus demonstrating the irrelevance of binocular disparity. Our poster allows viewers to experience this effect.

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