Opponent-process Theory - Visual Perception

Visual Perception

In the Young-Helmholtz Trichromatic Receptor theory, Hering postulated 3 independent receptor types, which differs from the Opponent-Process Theory because, in this theory, the 3 classes of receptors are each assumed to be composed of a pair of opponent color processes: white and black are a pair, as well as blue and yellow, and red and green. These three pairs produce combinations of colors for us through the opponent process. Additionally, according to this theory, for each of these 3 pairs, there occur three types of chemicals in the retina in which two types of chemical reactions exist. These reactions, in their building up phase, or anabolic process, would yield one member of the pair while in the destructive phase, or catabolic process, would yield the other. The colors in each pair oppose each other. Red-green receptors cannot send messages about both colors at the same time. This theory also explains negative after-images; once a stimulus of a certain color is presented, the opponent color is perceived after the stimulus is removed because the anabolic and catabolic processes are reversed. According to this theory, color blindness is due to the lack of a particular chemical in the eye. The positive after-image occurs after we stare at a brightly illuminated image on an regularly lighted surface and the image varies with increases and decreases in the light intensity of the background.