The women with super-human vision (BBC)

[eppur_se_muova]

David Robson

A tiny group of people can see ‘invisible’ colours that no-one else can perceive, discovers David Robson. How do they do it?

As Concetta Antico took her pupils to the park for an art lesson, she would often question them about the many shades she saw flashing before her eyes. “I’d say, ‘Look at the light on the water – can you see the pink shimmering across that rock? Can you see the red on the edge of that leaf there?’” The students would all nod in agreement. It was only years later that she realised they were just too polite to tell the truth: the colours she saw so vividly were invisible to them.

Today, she knows that this is a symptom of a condition known as “tetrachromacy”. Thanks to a variation in a gene that influences the development of their retinas, people like Antico can see colours invisible to most of us. Consider a pebble pathway. What appears dull grey to you or me shines like a jeweller’s display to Antico. “The little stones jump out at me with oranges, yellows, greens, blues and pinks,” she says. “I’m kind of shocked when I realise what other people aren’t seeing.”

Tetrachromats are rare enough, but Antico is particularly remarkable, since, as an artist, she is able to give us a rare view into that world. “Her artwork might tap into a structure that all of us can appreciate,” says Kimberly Jameson at the University of California, Irvine, who has studied Antico extensively. It’s even possible that she might suggest ways for more people to see the same way.
***
Proving that these people actually see the world differently has involved a two-decade journey, however. Although the relevant combination of genes does not seem to be especially rare – perhaps 12% of women might have four distinct cones – many of the people that Jordan tested just didn’t seem to show any differences in their perception. But by 2010, she had found a subject who perfectly acted the part of a tetrachromat. Jordan’s “acid test” involved coloured discs showing different mixtures of pigment, such as a green made of yellow and blue. The mixtures were too subtle for most people to notice: almost all people would see the same shade of olive green, but each combination should give out a subtly different spectrum of light that would be perceptible to someone with a fourth cone. Sure enough, Jordan’s subject was able to differentiate between the different mixtures each time. “When you ask them to discriminate between the two mixtures, a tetrachromat can do it very quickly. They don’t hesitate,” says Jordan.
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more: http://www.bbc.com/future/story/20140905-the-women-with-super-human-vision

[BrotherIvan]

1. You can take a color test online

It doesn't prove tetrachromacy, but it is interesting to note how you see color. Fun way to waste a few minutes.

http://www.xrite.com/custom_page.aspx?pageid=77&lang=en

I scored a zero and did not have to take breaks as some people have recommended because working with color is one of the biggest parts of my job. When working on retouching for giant cosmetics campaigns, I would always weight the female opinions higher than the males because men are truly bad at skin tones and subtle gradations. I always figured it was the red. But the more you work with someone intensely and figure out their color sense, you realize it is also a preference between warm and cool, the idea of what true white and true black are (very surprising) and the overall balance. I also learned that most of the people approving designs and talking about color were fairly low on their ability to differentiate color (but still had an opinion!).

Very interesting. I would love to take the true test.

[eppur_se_muova]

2. What color do you see in the center of each side of this cube ?

[BrotherIvan]

3. I assume all three are the same color

But computers are terrible at color rendition so the square against shadow does look and most likely is lighter/orange. That's why color systems such as pantone were created, because color is very difficult to pinpoint exactly and judging from different monitors is death.

I love optical illusions. I'm not a completely visual person as some people I know are, such as illustrators and VFX lighting. But I do find that when I am working intensely on a project that requires a lot of visualization, my spelling goes completely out the window, as if that part of the brain takes a back seat. I have never had a spelling problem, but it takes about three weeks to get back to normal and I find over time, it is becoming more of a problem.

Interesting. I hope people take the test and report their experience. I do admit to having a very good screen for my work and that likely made a difference.

[gristy]

4. Yes, they are all the same color

When I copied the image and isolated the 3 squares of interest, they were identical colors.

[Lionel Mandrake]

5. The scientific explanation of tetrachromacy is somewhat involved.

The story goes on to say that

the gene for our red and green cone types lies on the X chromosome. Since women have two X chromosomes, they could potentially carry two different versions of the gene, each encoding for a cone that is sensitive to slightly different parts of the spectrum. In addition to the other two, unaffected cones, they would therefore have four in total – making them a “tetrachromat”. For these reasons, it’s thought to be a condition exclusive to women, though researchers can’t totally rule out the possibility that men may somehow inherit it too.

This is about right, except for the last sentence. (Having only one X chromosome, men could not possibly be tetrachromats.)

The article cited in the OP fails to mention that in each cell in a woman, only one of the X chromosomes is active. Each X chromosome normally has a gene controlling the pigment in red cones and another gene controlling the pigment in green cones. Both types of gene are quite variable in the human population. This makes for some variety in the spectra of red and green pigments. (Technically, they are called long- and medium-wavelength pigments.) A woman's retina is actually a mosaic - like the skin of a calico cat. In some patches, one of her X chromosomes is active. In other patches, the other X chromosome is active. In principle a woman could be a pentachromat, i.e, she could have five different types of cones: two red, two green, and one blue (short wavelength). (The gene controlling the pigment in blue cones does not lie on the X chromosome, so it is impossible for anyone to have more than one type of blue cone.) Pentachromacy probably exists, but it has not been observed. Its effects would be very subtle indeed.

[eppur_se_muova]

6. Interesting, thanks. nt