Tuesday, May 19, 2015

Seeing a 100 million colors, 5 tetrachromats who see 100 times more color than you

Most humans have three types of cones in the retina of their eye, which help them to see a million colors by mixing and matching.

These are Red, Green and Blue Cones (RGB), like you use in your color hex codes. Each cone is most sensitive to a particular wavelength of light.
Women see more colors than men

Those who have three cones are called trichromats

Some people are deficient in one of their color cones, making them color blind bichromats.

  • Protanopes (Defective red)
  • Deuteranopes(Defective Green)
  • Tritanopes(Defective Blue)


But some people are now found to have four types of cones - making them tetrachromats.

Now, several species of birds, fish, amphibians, reptiles and insects are also known to have 4 types of cones. But among humans, this is so rare. And to test this is also quite difficult without specialised equipment.

Since 2012, a few tetrachromats have been found and studied. Since this extra cone is from one of the mutated X chromosome cone genes, it is seen only in women.

One of the tetrachromats is an artist called Concetta Antico.

When Concetta Antico looks at a leaf, she sees much more than just green. “Around the edge I’ll see orange or red or purple in the shadow; you might see dark green but I’ll see violet, turquoise, blue,” she said. “It’s like a mosaic of color.”

Based on Antico's genes, scientists have determined that Antico's fourth cone absorbs wavelengths that are "reddish-orangey-yellow"


There are tests for color blindness that you can take online, but a test for tetrachromacy is not that easy. The following image is supposed to show some characters in the colored circles for a tetrachromat, but I don't have access to a tetrachromat who can verify that.
Tetrachromacy test - what do you see in the circles ?

Tetrachomacy apparently does not get passed down to children, as only one X chromosome is given by the mother to the child. In fact, there is a risk of a child having color blindness, because the fourth cone gene is not a normal cone gene.

The above artist has a colorblind daughter.

Another tetrachromat is codenamed cDa29 to protect her privacy. She is a doctor in England and was the first of the terachromats to be discovered.

Also, Maureen Seaberg, (a synesthete) claimed to test positive for tetrachromacy in her genes, but further phenotypic testing results are not mentioned.

Interior designers Megan Arquette of Los Angeles and Susan Hogan of Pittsburgh are also thought to be tetrachromats.

So that makes 5 known tetrachromats in a world of 7 billion people.

If there are any tetrachromats out there, please do leave a comment. (And tell me what you see in the Red, Orange and Green circles)

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