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RESEARCH PRODUCT

Introduction: The World as a Stereogram

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This paper presents the historically most important theories of how visual perception is made spatial in the cognitive processing of the sensory input to the eye. All of them involve active engagement of the mind. Firstly, in the medieval theories physiological processes developed three-dimensional imagery in the brain, and active mental processing was needed to build coherence in the perceptual experience as a whole but not to yield the basic idea of spatiality. Secondly, according to Descartes, the eyes produced a unified two-dimensional visual image that was neurally transmitted to the inner surface of the brain. The innate conception of three-dimensional spatiality was superimposed intellectually on this image and thus all spatial perception involves mental judgment. Thirdly, Berkeley rejected innateness and claimed that the experiential three-dimensionality in vision was due to associating visual ideas to ideas of other senses, among which proprioceptive senses were the most important. Spatiality is thus not due to the basic visual experience itself in any of these three models.