DOI: 10.4324/9780415249126-W047-1
Version: v1,  Published online: 1998
Retrieved April 21, 2018, from

Article Summary

Vision is the most studied sense. It is our richest source of information about the external world, providing us with knowledge of the shape, size, distance, colour and luminosity of objects around us. Vision is fast, automatic and achieved without conscious effort; however, the apparent ease with which we see is deceptive. Since Kepler characterized the formation of the retinal image in the early seventeenth century, vision theorists have known that objects do not look the way they appear on the retina. The retinal image is two-dimensional, yet we see three dimensions; the size and shape of the image that an object casts on the retina varies with the distance and perspective of the observer, yet we experience objects as having constant size and shape. The primary task of a theory of vision is to explain how useful information about the external world is recovered from the changing retinal image.

Theories of vision fall roughly into two classes. Indirect theories characterize the processes underlying visual perception in psychological terms, as, for example, inference from prior data or construction of complex percepts from basic sensory components. Direct theories tend to stress the richness of the information available in the retinal image, but, more importantly, they deny that visual processes can be given any correct psychological or mental characterization. Direct theorists, while not denying that the processing underlying vision may be very complex, claim that the complexity is to be explicated merely by reference to non-psychological, neural processes implemented in the brain.

The most influential recent work in vision treats it as an information-processing task, hence as indirect. Computational models characterize visual processing as the production and decoding of a series of increasingly useful internal representations of the distal scene. These operations are described in computational accounts by precise algorithms. Computer implementations of possible strategies employed by the visual system contribute to our understanding of the problems inherent in complex visual tasks such as edge detection or shape recognition, and make possible the rigorous testing of proposed solutions.

    Citing this article:
    Egan, Frances. Vision, 1998, doi:10.4324/9780415249126-W047-1. Routledge Encyclopedia of Philosophy, Taylor and Francis,
    Copyright © 1998-2018 Routledge.

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