About one percent of people worldwide can see 99 million more colors than the average person, creating a more vivid world and seeing nuances invisible to most people.
Tetrachromacy is a rare genetic trait that gives people, primarily women, a fourth color-detecting cone in their retinas.
Most people 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 distinguish between several 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 shades you can see. Most people can see between 20 and 32 colors on the spectrum, bout people with tetrachromacy should be able to see at least 33 to 39 colors.
Most people can see between 20 and 32 colors, but people with tetrachromacy should be able to see at least 33 to 39 colors. However, take this test with a grain of salt as computer monitors cannot show the full range of colors that a test with a doctor can
Concetta Antico’s art captures the wide range of colors that tetrachromats can see. Her works are exhibited in San Diego, California. Courtesy of Concetta Antico
Concetta Antico, a tetrachromat, said she’s known something was different about her vision since she started teaching art classes: “I’d say, ‘Look at the light on the water—can you see the pink shimmering across it stone?”
The students nodded politely, but the colors she saw so vividly were invisible to them.
Tetrachromacy involves the light-sensitive retina at the back of the eye, which contains cells called photoreceptors that provide color vision.
The retina sends light signals to the brain via the optic nerve. When these signals reach parts of the brain responsible for vision, they are 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 that 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, giving 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 whether a person is tetrachromatic, although genetic testing is the only way to know for sure. Computer monitors can only take so many nuances, 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 what her world looks like in vibrant paintings in her California gallery.
She has known since she was young that her eyes saw the world differently than other children, and she knew from an early age that she wanted to pursue a career in art.
When she painted eucalyptus bark, Ms. Antico said the paint tubes flew and the result was a multi-colored tree with shades of purple, red, orange, blue and yellow
Concetta Antico’s vision is especially improved at night, as seen here. Courtesy of Concetta Antico
She told the BBC that while she was painting a eucalyptus tree, ‘the paint tubes were discolouring.
‘The yellows, the violets, the lime greens – I mixed violently on the palette and tried to produce all the color flows in the bark.’
She wasn’t able to learn for sure that there was actually anything different about her vision until she underwent genetic testing in 2012.
Genetic testing looks for mutations in two genes on the X chromosome that program the eyes’ ability to perceive 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 the specific gene mutations to occur.
People with these mutations can develop a fourth cone in their retinas that can detect wavelengths of light that fall between the ranges detected by the red and green cones (the long-wavelength and medium-wavelength cones).