Compare and contrast the trichromatic theory of color and the opponent-process theory of color vision, the evidence supporting each, and why both theories are needed in order to explain color vision

What will be an ideal response?

Answer will include that the trichromatic theory states that there are three types of cones, red, green, and blue, while the opponent-process theory states that vision analyzes colors into "either-or" messages of red or green, yellow or blue, and black or white. The trichromatic, or three-color theory, applies to the retina, in which three different types of cone have been found. Each contains a different type of iodopsin, a light-sensitive pigment that breaks down when struck by light. This triggers action potentials and sends neural messages to the brain. The three types of cones are most sensitive to red, green, or blue. Other colors result from combinations of these three. As predicted, each form of iodopsin is most sensitive to light in roughly the red, green, or blue region. Thus, the three types of cones fire nerve impulses at different rates to produce various color sensations. In contrast, the opponent-process theory better explains what happens in optic pathways and the brain after information leaves the eye. For example, some nerve cells in the brain are excited by the color red and inhibited by the color green. The occurrence of after-images also provides support to this theory. So both theories are "correct.". One explains what happens in the eye itself. The other explains how colors are analyzed after messages leave the eye.