Tetrachromats

June 12, 2013 @ DigitalJournal

Newcastle University neuroscientist Dr. Gabriele Jordan, recently announced that she has identified a woman who is a “tetrachromat,” that is, a woman with the ability to see much greater color depth than the ordinary person.

The first evidence that tetrachromats might exist came in 1948. A paper on color blindness written by the Dutch scientist HL de Vries, investigated color blind men who possess two normal cones and a mutant cone that is less sensitive to either green or red. This makes it difficult for such people to distinguish the two colors. De Vries incidentally tested the daughters of one of the color blind men and found that they could detect a wider range of hues of red than average persons. He found that while the color blind men had two normal cones and one mutant cone, the mothers and daughters of the color blind men had a mutant cone and three normal cones, that is, a total of four cones. He believed that the extra cone explained whey the women seemed able to distinguish a wider variety of hues of red. But De Vries did not have the opportunity to investigate the phenomenon further.

John Mollon of Cambridge University became interested in tetrachromacy in the 1980s. Dr. Gabriele Jordan who was working with Mollon, concluded that since color blindness or dichromacy is common, then tetrachromacy should also be common. She estimated that about 12 percent of women are tetrachromats. The researchers selected for their study mothers of color blind men who had three normal cones and one mutant cone, and tested them for the variety of hues they could detect. But the women showed no signs of ability to detect a greater variety of colors than ordinary persons. This led to the conclusion that the fourth mutant cone was inactive in these women. According to Discover Magazine, in 2007, Jordan, now at Newcastle, developed more powerful methods for identifying women with tetrachromatic vision. She chose 25 women all of whom had a fourth cone and tested them for tetrachromatic vision. She identified one woman tagged cDa29, who got all questions designed to detect an extended range of color vision correct. Jordan told Discover Magazine: “I was jumping up and down.” After 20 years of search she had finally found a truetetrachomat.

Read the whole article @ Digital Journal
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