The women with super-human vision (BBC) [View all]

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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.
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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