Tetrachromacy - Color Hypersensitivity

[waltky]

Uncle Ferd sees things when he gets into Granny's 'special' brownies...

The women with superhuman vision
5 September 2014 ~ 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.”

etrachromat women see shades that others think are monotone

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.

The question of whether we all see the same colours has a long history in philosophy and science. In the past, there seemed little reason to expect huge differences. We know that almost everyone has three types of “cone cells” in their retina that each respond to a different bandwidth of light. The colour of an object depends on the particular combination of those signals, but although the exact sensitivity may vary between people, overall one person’s colours should roughly match another person’s. The exceptions were thought to be colour-blind people, where one of the cones is faulty. With reduced sensitivity at certain wavelengths, they struggle to tell the difference between reds and greens, for instance.

Men are thought to be incapable of seeing this hidden world of colour

In theory, though, it could go the other way: according to some estimates, an extra cone would offer a hundred different variants to each colour that humans normally see. We know that this happens in nature: zebrafinches and goldfish both have a fourth cone that seems to help them differentiate apparently identical colours. About 20 years ago Gabriele Jordan at the University of Newcastle and John Mollon at the University of Cambridge proposed a way that it might be possible in humans too.

Comparing Antico’s painting with the original scene could give a hint of the extra shades she is seeing

The crux of Jordan’s argument lay in the fact 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.

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[Mr. H.]

Will Granny resurrect this thread 5 years from now?

 

[September]

Hey! Something like this is what happens when you trip on Shrooms or LSD. I always wondered what that was called, and why colors appear to be brighter and more vivid when you are trippin.
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