Post edited 4:31 pm – August 26, 2010 by keanani
I am posting George Berger’s posting 
, of August 20, 2010, post #57 within the General Discussion Forum, Topic~Introduce yourself and know the guidelines, here, to hopefully encourage discussion on such things and all that jazz.
The Psychology and Physiology of Colour Vision 
George Berger said:
@Keanani—I am posting these remarks on colour here, since you expressed an interest in the topic. Let me begin by describing the four major approaches to the psychology and physiology of colour vision.
1. The trichometrictheory of Hermann von Helmholtz. He postulated the existence of three types of visually receptive cells in the retina. Each type is sensitive to a range of illumination wavelengths (not: to colours), and the sensitivity varies within this range. Such a range is called a spectral distribution curve. He proposed that there are overlaps between the three ranges, and that each seen colour is correlated with positions in this system of ranges. That is, wavelength combinations determine seen colours.
2.The Great Austro-Hungarian physiologist and experimental psychologist Ewald Hering agreed with Helmholtz that three sorts of receptors exist, and agreed about the spectral distribution curves. But he argued that this is not enough to explain the existence of opponent pairs of colours: red-green, blue-yellow, black-white. Seeing one colour from one pair inhibits the seeing of its paired opponent. Moreover, the pairs function independently. So Hering postulated that the receptors must be connected in the brain such that this opposition and independence occur. The result was his opponent colour theory. We now know that the three receptor types exist, that there is an adequate triple of spectral distribution curves, and that the opponent structure is most likely present in normal persons. Abnormalities account for the kinds of colour blindness. There are some puzzling observations that might cause trouble for this reconciliation.
3. The late E. Land (inventor of the Polaroid Camera) attempted to develop computer algorithms for colour perception. His idea was to show that the illumination of a structured pattern in the visual world (not on the retina), together with facts about the pattern's geometry, determine the seen colour.
4. Finally, there are psychophysicaldescriptions of the entire domain of seen colours. These are mathematical techniques that show the detailed relations between colours. Psychophysics does not pretend to offer any physiological account; it is a bunch of orderings. I know three or four such schemes.
Well, these are the basic options. One main problem is to determine which choice fits in with our ever-increasing knowledge of eye and brain. I prefer opponent colour theories, for reasons I shall explain next time, when I give some references. I placed this post here because the philosophy thread is now occupied by discussions about intelligence and its role in Blindsight.
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