Suggestions that VR's real promise is a corroboration among the senses fail to consider the disjuncture between subordination and corroboration. Subordination to the visual really points to the coordination (and domination) by the visual of our other bodily faculties and senses. VR privileges sight, and other senses play a subordinate role to it. (Hillis, xxii, emphasis added)
To a great extent this claim is borne out by the fact that all branches of VR research currently employ some kind of HMD as a means of empowering vision.
Hillis traces this overvaluation of the visual on the part of VR researchers to the seminal influence of the work of perceptual psychologist J. J. Gibson. Throughout his career, Gibson sought to theorize the way we directly perceive aspects of the world by picking up information from what he calls the ambient light.8 As Jeremy Campbell explains:
Gibson held that all the information needed for perception ... is present in the structure of the light as it is reflected from objects and events in space. The objects and events give the light its specific organization as it reaches the eye. An observer is immersed, drenched in this information, and the perceptual system of the brain is attuned to pick up certain aspects of it, either by means of innate neural circuits or by the fine discrimination which comes with experience.9
As Hillis sees it, this notion of direct perception, together with the correlative notion that there are perceptual invariants immediately observable in the visual field, explains Gibson's impact among the VR research community.' Researchers saw in Gibson's work a mechanism for transferring perceptual experience characteristic of "real-world" perception to new, artificial environments: if real-world perceptual experience was grounded in biologically innate capacities to see perceptual invariants in the ambient light, all that would be necessary to carry perception into artificial environments would be to reproduce such perceptual invariants in the virtual domain.vi
One important facet of the complex influence of Gibson's work on VR research concerns Gibson's early theory of "texture-gradient mapping" which, Hillis suggests, furnished a model for the mapping of perceptual invariance" onto virtual environments (Hillis, 15; see also 125). According to Gibson, we directly perceive distance insofar as we detect the differences in texture gradient of objects located at different distances from us. Thus, we recognize the distance of an object from its texture relative to other objects within our visual field: the finer the texture is, the closer it is to us; the denser the texture is, the more distant it is. The important point here is that texture gradient does not define a cue that our brains employ in processing what we have seen, but is a spatial property of the environment itself. Once again, Campbell explains why:
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