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Tetrachromacy (‘Super Vision’)
What is tetrachromacy?
Tetrachromacy is often referred to as 'superhuman vision.' It is a condition where tetrachromatic people can see around 100 times more colours than the average person. Most people have three cone types at the back of their eyes which allow them to see colours. Those who are tetrachromatic have a fourth cone which enables them this ability to see more colours.
Tetrachromacy vs. trichromacy
The typical person is trichromatic, which means that they have three cones located near the retina, allowing them a range of color vision on the spectrum. The ability to see this range is known as trichromacy.
Photopigments in these cones are responsible for your ability to see the whole spectrum of colour. When photopigments react to specific colour wavelengths, this gives you the ability to see these colours.
The extra cone in functional tetrachromats features a photopigment which allows them to perceive more colours.
According to Jay Neitz, an ophthalmology professor at the University of Washington, tetrachromats may be able to see 100 million colours whereas trichromats can only see 1 million colours. This theory has also been suspected by neuroscientist Gabriele Jordan and her colleagues at Newcastle University.
What can Tetrachromats see?
Tetrachromats can see 100 times more colours than the average human due to their fourth cone, which gives them this heightened colour perception. They contain types of cone cells which are sensitive for reds and greens, blue and ultra-violet light. Tetrachromats see colours more intensely and are also able to see more variations in different colours.
Causes of tetrachromacy
Tetrachromacy is considered the result of a genetic mutation similar to that which occurs in colour-blindness. However, unlike those who are color-blind, the cone types belonging to a tetrachromat function just fine. The mutation which causes tetrachromacy happens on the x chromosomes. If the mutation occurs on both x chromosomes in a woman, then they are more likely to be tetrachromatic.
Tetrachromacy in males
Tetrachromacy does not exist in males. Men only have one x chromosome; therefore if a mutation were to occur, it would likely result in them being colour blind. Tetrachromatics are always female and carry the gene for colour blindness.
How do you tell if you have four cones in your eyes?
A genetic test can be carried out to find out if you have four cones in your eyes. However, these genetic testings won't necessarily tell you if the extra cone has given you the ability to see a broader range of colours.
Is there a test for tetrachromacy?
A colour match test is used to test tetrachromacy and involves the following:
- A set of two mixtures of colours is shown to those being tested
- A tetrachromat will be able to see differences in these sets of colours, whereas a trichromat will view them as the same.
- Those undergoing the test will be asked to rate the colour mixtures from 1-10 in regards to how closely the combinations look alike.
- The same sets of colour mixtures will be presented to participants at a different time, and they'll be asked to rate them again. They will not be told that they are the same colour mixtures.
A true tetrachromat will rate these colours the same each time.
There has been lots of research into tetrachromacy including the 2010 Journal of Vision Study, known only as cda29. This study identified a tetrachromat using colour testing. The study also stated that up to 12% of women have four cone types.
Nevertheless, research has also suggested that of this 12%, very few can perceive more colours.
In 2014 the Australian artist Concetta Antico openly identified herself as a tetrachromat. In an article published by the BBC, she shared her experiences of tetrachromacy. She told the BBC of how a grey pebble, for example, jumps out to her with many different colours, saying "I'm kind of shocked when I realise what other people aren't seeing."
While research on the condition points to its rarity, subjects like Concetta suggests that it exists nonetheless.