This psychological theory was introduced by Ewald Herring in 1878. an attempt to make up for some of the shortcomings of the more dated trichromatic theory. Both of these theories serve to supplement each other, while neither fully serves to explain the phenomena of color vision by itself. He observed that there are certain colors that we do not see in the same place at the same time, under any circumstances. Put simply, we cannot see reddish greens or yellowish blues, while we do see certain gradiations such as yellowish reds. He defined these "opposite" colors as complements. These produce gray tones when mixed.

Another shortcoming of trichromatic theory, is that it is impossible for a human being to verbally define all colors using a selection of only three possible (e.g. red, green, blue). Given the chance to use one more color by which to define the others, they usually pick yellow. This allows them to describe any color that they see quite accurately. The question, then, is of why four color names are needed to describe all color when there are supposedly only three color channels (as postulated by trichromatic theory).

So, what's the theory in short? Color perception depends on receptors that make antagonist responses to three pairs of colors. They are; red/green, yellow/blue, dark/light. The firing rate of nerve cells in the retina will increase in response to the former "colors," while it will decrease in response to the latter. Stimulation of, say, red, is inhibitory to green, because the firing rate of a nerve cell cannot increase and decrease at the same time.

The common experiment used to test this involves looking at an inverted image for about 30 seconds, typically consistent of an opposing pair of complementary colors on a black background, then to turn away and look at a blank white image. Where you saw green, you should see red, and vise versa. You can test this yourself by simply looking for a while at something which is a high intensity green, then looking away. You should see a pink afterimage somewhat in the resemblance of the original green image.

This theory was relatively unknown, until colleagues Leo Hurvich and Dorothea Jameson introduced the hue cancellation method in the 1950s to truly evaluate the opponent processing nature of color vision. The findings supported its claims. Due to a great degree of further testing, this theory is no longer questioned and now shares a place beside trichromatic theory in its attempt to explain color vision. Where you will find one theory, it is also rather likely that the other is not very far away.

note; this node is so named to avoid any confusion with solomon's "opponent-process theory," which concerns emotional experience.