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: 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 "either­or" messages of red or green, yellow or blue, and black or white. In fact, there are three types of cones found in the retina, each sensitive to either red, green, or blue. As predicted, each form of iodopsin within the cones are most sensitive to light in roughly the red, green, or blue region with the three types of cones firing nerve impulses at different rates to produce various color sensations.
Other colors result from combinations of these three. The evidence supporting the opponent-process theory includes the existence of afterimages, that is, fatigue caused by looking at red produces an afterimage of green or fatigue of blue producing an afterimage of yellow. There is also the impossibility of having reddish-green or yellowish-blue colors with the types of color weakness being red-green or blue- yellow, which supports the opponent-process theory. Thus, both theories are correct since the trichromatic theory applies to the retina, while the opponent-process theory explains what happens in the optic pathways and the brain after information leaves the eye.