Tetrachromats and Trichromats: What do you see?

Remember the gold dress phenomenon? How many colors can you count in the image above? Fewer than 20, you’re a dichromat. Between 20 and 32, you’re a trichromat. Above 32, you’re in the select few known as tetrachromats.

While the validity of this “testing” is up for debate based on questions about screen color variances in computers and other biological questions to do with the distribution of cones in our eyes and which chromosomes we possess. (Those with XY chromosomes have less of a chance of being a tetrachromat).

That being said, it’s still fun. And it tracks with historians’ take on human evolution and our perception of color. Up until 6,000 years ago, humans couldn’t perceive the color blue. It’s suggested that it wasn’t until we started making our own pigmentations that we discovered tetrachromatic color vision.

How many cones do trichromats use to see color?

A typical human (trichromats) has three types of cones near the retina that allow you to see various colors on the spectrum:

  • short-wave (S) cones: sensitive to short wavelengths – purple and blue.
  • middle-wave (M): sensitive to medium wavelengths – yellow and green cones
  • long-wave (L) cones: sensitive long wavelengths – red and orange

What is a tetrachromat?

Tetrachromats have a fourth, extra cone. But not all people with a 4th cone are tetrachromats. Tetrachromacy is quite rare. Trichromats see 1 million color variations. Tetrachromats see 100 million. True tetrachromats consist of less than 1% of the human population.

And they are predominantly a tetrachromat woman like artist Concetta Antico. So from this female population, the best way to identify potential tetrachromats is by looking at your mother’s male relatives.

A color vision researcher at New Castle University demonstrated that the most likely candidates for tetrachromacy are those who carry the gene for very mild color vision deficiency (or mild color blindness).

Although the above test might not be scientifically valid, it still illustrates the spectrum of average human perception. Even if it’s only on a remedial scale. If you’re interested in seeing if you’re a true tetrachromat, you can get tested for genetic mutations along the “X” chromosome. Well, that and a painstaking color matching test.

Then what is the story with color blindness?

Color blind is not an accurate term. And the term is misleading because it is not actually blinding. The difference is these folks simply cannot see as much of the color nuances as another. A more accurate term for this type of difference in vision would be “color deficient.”

This is because the range of colors are seen when different wavelengths of light interact with the cone types in our retina. These color receptors send signals to our brain. There are three types of cone and two of them pick up a red, blue, or green light. The other cone cells pick up additional colors like yellow and ultraviolet light.

8% of the US male population is color blind – 95% of them with red or green receptor problems.

John Shearer

People who have a problem with color differentiation can’t distinguish between those types of color. This is why many people confuse green and blue or purple and pink.

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