opponent-process theory
Summary
Opponent-process theory says color is coded by paired channels (red–green, blue–yellow, black–white) in which the two members oppose each other in the same cells. It explains negative afterimages. It works alongside trichromatic theory: cones at the receptors, opponent processing in later neurons.
Detail
Meaning: Proposed by Hering, the theory holds that color perception depends on three opposing pairs: red versus green, blue versus yellow, and black versus white. In each pair, one color excites a cell and the other inhibits it, so a channel signals one member or the other at a given moment. This is why we do not perceive a reddish green or a bluish yellow. The opponent cells are found after the cones, in retinal ganglion cells and the thalamus (lateral geniculate nucleus). A second MCAT sense, Solomon's theory of emotion, says a strong emotional state is followed by an opposite state that strengthens with repeated exposure, which explains drug tolerance and withdrawal.
On the MCAT: A passage describes staring at a green image, then looking at a white surface and seeing a red afterimage. The reasoning is that the green side of the pair becomes fatigued, so the red side dominates the signal. Questions also ask which theory accounts for a given finding: three cone pigments point to trichromatic theory, while afterimages and the absence of reddish green point to opponent-process theory.
Common confusion: Students treat the two color theories as rivals. They are not. Trichromatic (Young-Helmholtz) theory describes three cone types at the receptor stage, and opponent-process theory describes how later neurons recode those signals. Both are accepted. Also, the afterimage is the opposing color, not the same color.
Sources
- Psychology (Myers)
- Sensation and Perception (Wolfe et al.)
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.