Color, Depth, and Size

97 Tri-chromatic vs. Color Opponent processing

Learning Objectives

Be able to describe the trichromatic theory of vision.

Be able to describe opponent process theory.

Understand reconciliation of these theories in the retina.

The trichromatic theory states that our cones allow us to see details in normal light conditions, as well as color. We have cones that respond preferentially, not exclusively, for red, green, and blue (Svaetichin, 1955). This trichromatic theory is not new; it dates back to the early 19th century (Young, 1802; Von Helmholtz, 1867). This theory, however, does not explain the odd effect that occurs when we look at a white wall after staring at a picture for around 30 seconds. Try this: stare at the image of the flag in Fig.10.2.1. for 30 seconds and then immediately look at a sheet of white paper or a wall. According to the trichromatic theory of color vision, you should see white when you do that. Is that what you experienced? As you can see, the trichromatic theory doesn’t explain the afterimage you just witnessed. This is where the opponent-process theory comes in (Hering, 1920). This theory states that our cones send information to retinal ganglion cells that respond to pairs of colors (red-green, blue-yellow, black-white). These specialized cells take information from the cones and compute the difference between the two colors—a process that explains why we cannot see reddish-green or bluish-yellow, as well as why we see afterimages. Color blindness can result from issues with the cones or retinal ganglion cells involved in color vision.

Reconciliation between these two theories lies in the retina. We have 3 kinds of photoreceptor pigments, but the circuitry of the retina combines them so ganglion cells respond along a red/green axis or along a blue/yellow axis.

 

Fig.10.2.1. Stare at the center of the Canadian flag for fifteen seconds. Then, shift your eyes away to a white wall or blank piece of paper. You should see an “after image” with a different color scheme. (Provided by: General Psychology. License CC-BY-NC-SA)

 

Here are two Audiopedia videos on trichromatic theory and opponent process theory:

 

CC LICENSED CONTENT, SHARED PREVIOUSLY
Noba project, General Psychology: An Introduction, Chapter 4: Sensation and Perception
Provided by: GALILEO, University System of Georgia
URL of source: https://oer.galileo.usg.edu/cgi/viewcontent.cgi?article=1000&context=psychology-textbooks
License of original source: CC BY-NC-SACheryl Olman PSY 3031 Detailed Outline
Provided by: University of Minnesota
Download for free at http://vision.psych.umn.edu/users/caolman/courses/PSY3031/
License of original source: CC Attribution 4.0

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Introduction to Sensation and Perception by Students of PSY 3031 and Edited by Dr. Cheryl Olman is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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