May 17, 2013

Science facts: Human tetracromacy

Do you perceive infestiminal nuances of color invisible to most humans?

One of my current areas of interest is human tetrachromacy. In a nutshell, most humans have three cone cells (or cones) in their eyes, which allow them to perceive approximately 100^3 shades of color (each cone perceives about 100 shades). Most mammals are dicromates (i.e. with two cones), and can thus perceive 100^2 shades. However, some women (genetically, it's apparently a XX trait) appear have four cones - and can thus perceive 100^4 shades of color.

As per a comprehensive article in Discover magazine, Dr. Gabriele Jordan at Newcastle University is to be the current leading authority on human tetrachromacy. I wonder how many emails a day she gets from people saying "I'm a tetrachromat! Study me!" - but who then turn out to have supremely ordinary vision. Since it appears that Jordan has only found one true tetrachromat thus far...

There aren't any conclusive online tests I could find which can fully diagnose tetracromacy. X-rite, the company behind Pantone, has an online exercise where you sort shades of color into their correct order. I found it incredibly tedious but passed with...flying colors and just missed the perfect score of 0. According to this article on Apartment Therapy, this might make me a tetrachrome...but then on Tumblr there is this image which apparently contains shapes visible only to tetrachromes, and I just see spots. So it's likely the same thing that happened to me when I diagnosed myself with synesthesia as a youngster, while in reality I'm probably just overly sensitive to light, colors, sounds, textures, smells, and sounds.

The information on tetrachromacy is relatively sparse - I did find a handful of articles through Google Scholar (some have restricted access):

G. Jordan, J.D. Mollon
A study of women heterozygous for colour deficiencies
Vision Research, Volume 33, Issue 11, July 1993, Pages 1495–1508

S.M. Hood, J.D. Mollon, L. Purves, G. Jordan
Color discrimination in carriers of color deficiency
Vision Research, Volume 46, Issue 18, September 2006, Pages 2894–2900

Vitali V. Gavrik
Tetrachromacy of human vision: spectral channels and primary colors
Proc. SPIE 4421, 9th Congress of the International Colour Association, 315 (June 6, 2002)

Sutherland, R.
Aliens among us: Preliminary evidence of superhuman tetrachromats

Oh, and this artist has a website which also discusses how her certified tetracromacy has influenced her work.

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