One in 30 people can see 'invisible' colors that no-one else can

One in 30 people can see 'invisible' colors that no-one else can

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About one percent of people worldwide can see 99 million more colors than the average person, creating a more vivid world, seeing hues invisible to most humans.

Tetrachromacy is a rare genetic trait that endows people, primarily women, with a fourth color-detecting cone in their retinas.

Most humans have three cones in their eyes that detect variations of red, blue, and green along the spectrum of visible light. Tetrachromats have four.

Tetrachromats can differentiate between more colors within the range of light visible to humans, allowing them to distinguish more subtle variations of color.

To see if you might be a tetrachromat, look at the spectrum below and see how many hues you can make out. Most people can see between 20 and 32 colors on the spectrum, but people with tetrachromacy should be able to see at least 33 to 39 colors.

Concetta Antico, a tetrachromat, said she has known something was different about her vision since she began teaching art classes: 'I’d say, "Look at the light on the water – can you see the pink shimmering across that rock?"'

The students would nod politely, but the colors she saw so vividly were invisible to them.

Tetrachromacy involves the light-sensitive retina in the back of the eye, which contains cells called photoreceptors that provide color vision.

The retina transmits light signals to the brain via the optic nerve. Once those signals reach parts of the brain responsible for vision, they become converted into the images we see.

These photoreceptors consist of rods and cones. Rods allow the eye to sense light and see in the dark, while cones allow the eye to see and differentiate colors.

Most people are trichromatic, meaning the three types of cone cells in their eyes are sensitive to three wavelengths of light – red, blue, and green. The combination of signals from these three allows us to see a wide range of colors.

Tetrachromats, meanwhile, have four types of cone cells in their eyes. The fourth cone is sensitive to a wavelength between red and green, which gives some people the potential to see a far wider range of colors than trichromats.

Up to 12 percent of women and eight percent of men may be tetrachromats.

Certain visual tests including the one pictured can help determine if a person is tetrachromatic, though genetic testing is the only way to know for certain. Computer monitors can only so so many shades, so take the online tests with a grain of salt. Doctors often perform these tests in person to get a more accurate result.

Ms Antico conveys how her world looks in vibrant paintings at her California gallery.

She has known since she was young that her eyes saw the world differently than other children’s, and she knew from an early age that she would pursue a career in art.

She told the BBC that while painting a eucalyptus tree, ‘The tubes of paint were flying.

‘The yellows, the violets, the lime greens – I was ferociously mixing on the palette trying to produce all the streams of color in the bark.’

She wasn’t able to learn for certain that there was in fact something different about her vision until undergoing a genetic test in 2012.

Genetic testing looks for mutations in two genes on the X chromosome that program the eyes’ ability to pick up red and blue.

Since the genes are on the X chromosome, tetrachromacy is more common in females with two X chromosomes and may carry different versions of the opsin genes.

In contrast, males have only one X chromosome, therefore they have less opportunity for those specific gene mutations can occur.

People with these mutations can develop a fourth cone in their retinas, which can detect wavelengths of light that fall between the ranges detected by the red and green cones (the long-wavelength and medium-wavelength cones).