Reality and its millions of colors. We know that not all animals look the same: from dolphins, whales, bats or hamsters, who only see in black and white, to the eagle (which can see about eight times more than us) or the owl (the best night vision). But is that even among human beings there are differences.
Not everyone sees the same number of colors. We could say that statistically speaking there is a normal view, a deficient and a privileged one. The great most men and women are trichromats. Then, at the ends, there is a group with a less rich view, the dichromatsand another with the best view, the tetrachromats.
cones and rods
Before, to describe how good or bad they all see, let’s know how we see colors. It is thanks to the cones of the eye. They are photosensitive cells that are located in the retina and are responsible for color perception. There are three types of cones: those that are sensitive to red light, those that are sensitive to blue light, and those that are sensitive to green light.
Humans have a second type of photoreceptors that are stimulated by light. are the canes, which are so sensitive that they can respond to a single photon. They are the cells that help us see at night or when there is little light.
The spectrum visible to light radiation
Science calls the light radiation that our photoreceptors perceive the visible spectrum. Actually, we don’t see much. We cannot see things that are around us like ultraviolet, infrared, gamma rays, X-rays, or microwaves. They are beyond the evolutionary capacity of our eyes.
Our cones and rods perceive a very narrow band of the total spectrum electromagnetic: wavelengths ranging from 400 nanometers in amplitude (we see it as purple) to 750 nanometers (red).
Most perceive about a million different shades. Are trichromatic people, that is, they have three types of cones. In this way they are able to see all the resulting combinations of the three primary colors: green, red and blue. They can appreciate up to 2.5 million shades of color.
When we look at an object, we see it as a certain color because, due to its physicochemical characteristics, it absorbs some wavelengths of the visible spectrum and reflects others”
We call the cones that respond to the longest waves in our visible spectrum cones for red. Those that are stimulated with the medium waves are the cones for the verde and those that respond to the narrower waves are the cones for the azul.
“When we look at an object, we see it as a certain color because, due to its physicochemical characteristics, absorbs some wavelengths of the visible spectrum and reflects others. The latter are the ones that reach our photoreceptors and stimulate the corresponding cones”, explains Conchi Lillo, researcher of visual pathologies and tenured professor at the Faculty of Biology of the University of Salamanca.
dichromats and tetrachromats
Compared to most trichromats, dichromats only have two types of cones in the queen These people have trouble perceiving red, green, and less frequently blue. Instead, people tetrachromatics have four different types of cones and thus can distinguish up to 100 million tonalities.
Whether or not we are tetrachromats depends on genetics. In people with two X chromosomes (mostly female) It has been seen that mutations in one of the copies of the genes to distinguish between green and red on one of the X chromosomes can produce a fourth type of cone.
This is because these tetrachromats have a copy of the correct protein and another copy of the mutated one in that fourth type of cone. If the two proteins that are generated, the correct one and the mutated one, work properly, this “plus cone” allows them to have an extraordinary chromatic vision, details Lillo.
How do I know if I am a tetrachromat?
Since people with two X chromosomes are mostly female, it is thought that tetrachromatic vision It is an exclusive condition of women. However, the researchers cannot totally rule out the possibility that a small percentage of men have also inherited this privileged type of vision.
For now, tetrachromatic vision is an exclusive condition of women
In any case, there is no official tetrachromacy test. In addition, with the current means it is impossible to do these tests onlineSince the digital screens are based on RGB technology which is a trichromat system of color representation, recalls the optometrist Daniel Aznar Granados from his website myopia control.
How many tetrachromat people are there?
According to studies from the University of Newcastle, few human beings, basically women, could be carriers of that fourth cone, but so far very few have been found. In this English university they maintain the research and a portal with its results: Tetrachromacy Project.
For Professor Lillo, the issue is difficult to evaluate. However, she points to studies that indicate that 12 to 50% of people with XX chromosomes and up to 8% of XY could be tetrachromats.
The person with the best view in the world
The person best known for have tetrachromatic vision is the Australian artist Concetta Antico. She was an art teacher and took her students to the park for an art lesson. Once there she used to ask them about the different shades of colors that she could distinguish.
“I’d say, ‘Look at the light in the water: can you see the pink shimmering through the rock? Can you see the red on the edge of that sheet?‘” he told the BBC in 2014. They nodded in agreement.
But over time, Antico understood that they were doing it out of courtesy. Actually, her students did not distinguish the colors that she saw so vividly. “I was very surprised when I realized which the others are not able to see“said the artist.