Toward a new theory of stereopsis
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Humans can achieve an unambiguous perception of depth and 3-dimentionality with one eye or when viewing a pictorial image of a 3D scene. However, the perception of depth when viewing a real scene with both eyes is qualitatively different: there is a vivid impression of immersive space and tangible solid form. This perceptual phenomenon is called ‘stereopsis’ from the Greek words for ‘solid’ and ‘appearance’ and has been among the central puzzles of perception since the time of da Vinci. After Wheatstone’s invention of the stereoscope, stereopsis has conventionally been explained as a by-product of binocular vision, though several key perceptual observations challenge this explanation. Here, I present an alternative view that stereopsis is the perception of the precision of egocentric spatial scale estimates. By analysing recent empirical evidence, novel visual demonstrations, and current understanding of depth computation, I argue that stereopsis cannot be explained solely on the basis of binocular vision or visual parallax. Alternative explanations linking stereopsis to the conflict/coherence among depth cues or the magnitude of perceived depth are also not supported. Instead, variations in stereopsis for both pictures and real scenes are better understood as a function of the availability and reliability of egocentric distance information required to scale perceived depth and size precisely. Since conscious awareness of this precision can guide the planning of motor action, the theory provides an account for the phenomenal characteristics associated with stereopsis. The implications of the theory for 3D media and virtual reality, the evolution of binocular vision, and the philosophy of perception are discussed.
Vishwanath , D 2014 , ' Toward a new theory of stereopsis ' Psychological Review , vol 121 , no. 2 , pp. 151-178 . DOI: 10.1037/a0035233
© 2014. American Psychological Association. This article may not exactly replicate the final version published in the APA journal. It is not the copy of record.
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