Recently there was a schism on the internet between people about the color of a dress.  That led to all kinds of scientific articles about how we perceive color differently, memes about white and gold things and black and blue things, and finally, eventually, this.

Screen Shot 2015-03-02 at 4.13.41 PM

That is from an article on LinkedIn, written by a woman named Diana Derval, who claims to be an expert in neuromarketing, whatever the fuck that is.  The title of the article looks like this:

Nothing says legitimate scientific knowledge like a winky face with its tongue out.

Nothing says legitimate scientific knowledge like a winky face with its tongue out.

This is already almost a hundred percent incorrect, but in order to explain why, I need to give you a little anatomy lesson.

Vision starts in the eye.  There are three sets of cells in the eye called “cones” and one set called “rods.”  Rods only have one kind of light-sensitive pigment in them, which means they can only tell how much light is coming in, not what color it is.  They are far more sensitive than cone cells and are almost entirely responsible for low-light vision, but have little to no role in color vision.

The majority of people have three cones, called L, M, and S for the long-, medium-, and short-wavelength light they detect.  After the pigments pick up light, they are sent to the brain along three channels, one for each color.  L corresponds with red, M with green, and S with blue.

Roughly one in sixteen men is what’s called red-green colorblind, which is a slightly misleading term.  The correct term is anomalous trichromacy, meaning they have two fully functioning sets of cone cells instead of three.  The S (blue) set is fine, but either the M (green) has sensitivity shifted toward the red portion of the spectrum, or the L (red) has shifted toward the green.  Importantly, though, the brain does not know that this has happened.  This is a genetic condition that affects the eyes, but not the color-sensing portion of the brain.  The brain assumes that each cone is sending it the correct color and builds images accordingly.

I, for example, am deuteranomalous.  I have a perfectly functional set of S cones and a perfectly functional set of L cones, but my M cones are shifted toward the L end of the spectrum.  This means, theoretically, that I am less sensitive to green light than a person with normal vision, but I can’t tell.  As far as my brain is concerned, the signals are coming through fine.

Here’s an example.  Imagine a gray square, composed of equal parts blue, red, and green light.  Then you turn up the red and blue light, making the gray square a sort of dull magenta color.  To you, that square is now magenta. My stupid deformed M cones, however, are detecting red when they shouldn’t be, so they detect the increase in red light as well.  They report back to the brain that the green levels have gone up, when they haven’t. My brain is now getting signals that all three channels of light have increased in magnitude and the square is now a brighter shade of gray.  It’s not.  It’s pink.  But I can’t tell.  Want to see that in action?

Screen Shot 2015-03-02 at 5.04.32 PM

This is a graphic to test my particular flavor of color blindness.  My coworker assures me that the sky inside the circle is pink, but I can’t tell because my dumbfuck M cells think that the increase in red and blue is an increase in all three colors, which cancels out.  I can tell that it’s not exactly the same as the other sky, but it’s more of a texture than a color.  She tells me that the grass in the circle is yellower (because red light was added to the existing green), but I can’t tell for the same reason.  The gist of it is that if something is pure green, it looks paler to me.  If you add red to something, I can’t tell.  Dark blue and purple are a nightmare. Traffic lights look very pale, almost blue.  Dull greens look brown because I can’t see the green part.  And so on.

This brings me back around to tetrachromacy, or the presence of four sets of cone cells.  A Dutch researcher in the 1940s noticed that the mothers and daughters of deuteranomalous men like myself all had normal color vision.  He knew that the genes responsible for cone cells came from sex chromosomes, which left two possible explanations.  If the mutated M cells came exclusively from the father, all fathers and sons of deuteranomalous men would have the same condition, which wasn’t the case.  If they came in equal part from the mother, then deuteranomaly would be similarly present in women, which wasn’t the case.  He concluded, therefore, that the mothers and daughters of deuteranomalous men must have a fourth set of cells, giving them three functional ones and one mutant.  He hypothesized that women with four functional sets of cells might exist, but it wasn’t the point of his research so he didn’t look into it.

This has been a long wall of text. Here is a cat being friends with a horse.

Fast forward to 1980, when two researchers became intrigued by the idea of four-coned women.  They knew that anomalous trichromacy was common, which meant that four-coned women must be common as well.  They sought out the mothers and daughters of colorblind men and had them take a color matching test.  In such a test, the subject mixes levels of red and green light to match the yellow light provided.  Colorblind men will have to add more of either red or green to compensate for their defective cones, and people with normal vision will be able to match the colors correctly.  People with four cones, theoretically, would be able to tell the difference between true yellow light and light made by mixing red and green, and would therefore be unable to make a match.  That wasn’t the case.  The researchers found plenty of women with four sets of cones, but none of them had more sensitive color vision than the average trichromat.

In 2007, one of the researchers tried a different technique.  She flashed three colored circles in front of her subjects’ eyes.  A trichromat would have been unable to tell them apart, but a tetrachromat should have been able to recognize that one of the circles was actually a very subtle mix of red and green, rather than a solid yellow color.  Only one woman was able to pass the test.  Which brings me to my point (1100 words later):

If two researchers who dedicated their careers to the task were only able to find one functional tetrachromat in 27 years, do you really think that a test on LinkedIn written by a marketing professor is going to help?

Obviously, the answer is no.  But there’s more bullshit here.  First, the title.

25% of people are tetrachromats

Lies.  It’s something like 12% of women, which is 6% of people — and is probably more common in women of Northern European ancestry, so that number’s even lower worldwide — and it’s so rare that women with four cells can actually use them that we can’t even put a number to it.  Only two women in history have ever been empirically confirmed as functional tetrachromats.

and see colors as they are

That’s a preposterous thing to say.  Everyone’s cones see slightly differently already due to genetic variation, so theoretically the same wavelength of light looks infinitesimally different to every single person.  The only reason color blindness is a thing is that color blind people can’t distinguish between certain colors, not that they’re seeing them wrong.  Sure, you can empirically say that a certain LED bulb emits light at a wavelength of 581nm, but what does that look like?  No one can really say for sure.  There is no such thing as colors “as they are.”

You see less than 20 color nuances: you are a dichromats, like dogs, which means you have 2 types of cones only. You are likely to wear black, beige, and blue. 25% of the population is dichromat.

Horseshit.  Dichromacy affects less than 3% of males and .03% of women.  That’s about 1.5% of the general population.

You see between 33 and 39 colors: you are a tetrachromat, like bees

No part of that is true.  Firstly, you can’t diagnose tetrachromacy on a computer screen AT ALL because computer screens are made up of combinations of only three different colors of light.  It is literally not possible for an LED computer screen to generate the kind of nuance that distinguishes tetrachromats from trichromats.  Secondly, bees see in ultraviolet, meaning their extra color vision is in a wavelength that no human being (or even mammal)* has ever seen.  Being a tetrachromat in the visible spectrum does not mean you can see what bees see.  And thirdly, BEES ARE NOT TETRACHROMATS. Bees are trichromats, with cones in what we might call the green-yellow, blue, and UV portions of the spectrum.  They still only have three cones.

It is highly probable that people who have an additional 4th cone do not get tricked by blue/black or white/gold dresses, no matter the background light

Die in a multicolored fire.  Let me say this one more time: that dress is a photo on a computer screen, taken on a digital camera.  The screen on your computer is only capable of generating three wavelengths of light, and all others are projected as mixtures of those three.  The sensor in your camera only records three wavelengths of light (because that’s what you see in), and all others are a mixture of those three.  ANY COLOR IN THE WORLD THAT IS NOT A SPECIFIC WAVELENGTH OF RED, GREEN, OR BLUE is shoehorned into a combination of those three by your eyes, your brain, your camera, and your screen.

This graphic is like testing your depth perception with one eye closed***.  It is fundamentally impossible.  It is stupid, insulting, and worst of all, it is popular.  Stop it immediately.

*[EDIT 03/10: Turns out a whole shitload of mammals can see in UV, but humans are not among them.]**
**[EDIT OF THE EDIT 03/12: Turns out that some humans can see in UV (a condition called aphakia) some of the time.  UV is blocked by the lens, so if the lens is fucked up due to surgical removal, a perforating wound or ulcer, or congenital anomaly, UV light can hit the retina.  It is thought that Claude Monet was aphakic because he painted flowers in a way that a person with normal vision shouldn’t have been able to see.]
***[EDIT 03/12: It is possible to percieve depth to a small extent with one eye based on perspective, size comparison, motion, and the flexing of the lens in the eye to adjust focal length.  TESTING depth perception using one eye would still be dumb.]
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  1. Anna says:

    Thank you for that great article. For I’m a real tetrachromat, I have hours of discussing about colors of dresses, pictures, walls, flowers, an so on. And some of the persons I talked with, think they’re tetrachromats too, because of counting that stupid, compressed pixels, though they can’t divide yellow from orange -.- Great, great thanks!


      Some people with only 3 types of cones can tell the difference between some colors that look exactly the same as each other to other people because they work with them on a regular basis, so unless you have gone to a doctor and asked them, you just might have the normal amount of cones.

  2. DamienDon't says:

    So wait, you’re saying I don’t have super sight?

  3. anie says:

    I couldn’t stop laughing at “Die in a multicolored fire” that was the best part of the article so far!! hahaha. I really liked this article, you made it easy and interesting, good job.

  4. If we’re just going by number of cone variations, the odds that a female carrier would *not* be a tetrachromat are pretty low. Which one of the inherited X chromosomes is expressed in a particular cell is determined by what amounts to a coin flip, so the retinas of a carrier would be a mosaic of normal-L, normal-M, normal-S, and mutant-M/L, depending on whether she carried protanomaly or deuteranomaly. Chances of zero cells in either eye expressing the mutant chromosome instead of the normal one are really not that good.

    Whether this is of any practical value is another matter. Red-green colorblindness runs on my mother’s side of the family, and my eyes have subtly different white balances, so unless something truly new and bizarre has happened, I must be a carrier, and each eye must’ve gotten a slightly different ratio of mutant to normal cones. The mutant cones don’t respond to any wavelengths outside the normal gamut, they just respond differently to the same ol’ wavelengths everything else gets; if there’s any practical value in it, it’s probably that I’ve learned to notice when I’ve got a slightly different signal coming in from each eye, and discriminate between colors in the overlap area based on the contrast.

    I am one of those irritating people who can correctly name eleventy-nine colors and thinks there are different shades of black and white, but this is mostly because I’m observant, I practice, and I care. And I can’t do it on a poorly-compressed JPEG.

    (I am definitely keeping the link to this article around; you have one of the clearest explanations of why all the stuff in the red-green area of color blends into one smooth gradient of gred for you, and why you deem odd bits of it ‘gray’ instead.)

  5. Marie Schmidt says:

    I wish that I could know for sure if I’m a tetrachromat. I just took the online color test, and i got the score: 0 (which is a good thing), I have also completed all of the puzzles in blenduko 2 (with a time below the world average on all of them) and i have a score on 100 in their color IQ test. But I don’t know for sure though. Is there any way I can find out?

    • DangerOnion says:

      Not on a computer screen, no matter what the venue. To find out if you’re a functional tetrachromat, you’d need to compare yellow light that’s truly yellow—something computers can’t possibly produce—and yellow light that’s a mixture of red and green. That probably means xenon bulbs and specific gels, or maybe carefully calibrated printing, I’m not sure of the actual experimental process. But I can save you some time and tell you with near-absolute certainty that you’re not a (functional) tetrachromat. Almost no one is, to the point that it took thirty years of study to even confirm that such a thing was possible.

      • May Herondale says:

        They gave me a colour test like this when I was younger because my eye doctor suggested it to see if I was colour blind. When I was younger my mother would mix paint for her hobbyist paintings. I (apparently) asked on multiple occasions what she called the colours. She would reply with like Purple and I’d start an argument that it wasn’t purple. That it was something else. (Can you imagine me rolling my eyes at this point? I got put in time out more than once for having this argument with my mum.) Eventually, it snowballed into this fear that I was colour blind. (I had also freaked her out by coming out with white hair and pasty white skin. She assumed I was albino. My mother is a freak. I’m not albino. I was just pasty all my childhood because the outdoors sucked. I wanted to read more than play outside. It happens.)

        I digress. Well, the eye doctor did a colour test on me. I got to sit in a box and had colours flashed on a wall and I had to identify them. At one point, he flashed a colour and I said I didn’t know. So he showed me again and asked me to describe it. He was testing for red deficiency I think or something. But It was a mix of green and red or whatnot. (It’s been about 20 years at this point.)

        All in all, he suggested to my mother that I might be something like Tetrachromatic. Because I was picking up subtle changes in hues of light that (apparently) should not have been possible for seven or eight year old me.

        I don’t know for sure even now. My crazy as a bat mother told all her friends her daughter could see more colours than the average person. And I died of embarrassment every time. I didn’t even think about it after I became an adult and this stupid gradient test was showing up and I’m like, HOW CAN YOU THINK A MONITOR IS A GOOD MEDIUM FOR THIS BULLSHIT?! To even think about diagnosing DIchomatic, you need to go to optometrist. For any eye related test, you should see a licensed professional. Not your computer monitor with a gradient scale my 5 year old nieces could put together.

        It’s like people who self diagnose from WebMD.

  6. Shay Fowler says:

    I would think that it would be easy to figure out now days. Does the television or computer screen look different or bland compared to real life?

    For me, the TV and computer screen look perfectly accurate as compared to what I see on a sunny day. I would assume that I can only see the red/green/blue – as that’s all that the TV projects and it looks real to me.

    Does this mean that I’m seeing these things accurately? I’ll never know that.

    My son was color blind and it took an eye dr to figure that out. He favored pink shirts and everyone thought that he was courageous and making a bold statement. Turned out that he had no idea that he was wearing pink. He got a lot of compliments, so he went with it.

  7. Bryce says:

    Presumably one way to infer if you are a tetrachromat would be if there are colors you see in real life that never appear correct on a computer screen.

  8. Cat Bowen says:

    I actually, honestly am a Tetrachromat, I do see more colors than normal. I respect you trying to do all this research but this article is not really true. It seems ignorant and rude excluding the Tetrachromats saying they aren’t what they are… Its in the title so don’t tell me that’s not what this article is about.

    • DangerOnion says:

      With all due respect, no you’re not. Functional tetrachromacy is exceptionally rare. All the scientific evidence that’s ever been done on the subject supports that. And in thirty years of research, one single person has been found to have functional tetrachromacy. Chances are, you’re not that person. Maybe you also have it. But unless you’ve been tested in an appropriate laboratory setting, I feel 100% comfortable rejecting your claim to “see more colors than normal.”

      And finally, you think it’s rude of me to exclude tetrachromats based on an enormous amount of research, freely available online, and the fact that it is FUNDAMENTALLY IMPOSSIBLE to diagnose tetrachromacy on a computer screen, but you feel completely confident dismissing my work by fiat, telling me that what I’ve written is “really not true” based on what you think you know about your own eyesight. Maybe you should use your special eyes to take a good hard look at yourself and how you make arguments.

      I’ll make you a deal. If you can find one single thing in my article that’s objectively untrue, logically fallacious, or at all incorrect, point it out. I’ll issue a correction. If you have proof—real, scientific proof—that you’re a functional tetrachromat, contact Gabriele Jordan at the University of Newcastle immediately. I’m sure she’s dying to hear from you, especially since she’s the only person who’s ever devised a test for what you claim to have. If you prove me wrong, I’ll edit this post with a full redaction of whatever I screwed up on, like I already have with the parts about UV light.

      But until that happens, I’m going to assume that you, like the delusional woman who published this graphic in the first place, are grossly misunderstanding what tetrachromacy actually is, and whether you in fact have it. I look forward to hearing from you.

      • The1stDwarf says:

        Your article is excellent. Any of your colour deficit hasn’t stopped you from have an brilliant mind. My son is deuteranomalous and I know what a conversation looks like for him with those who do,and do not get what that’s like. Despite that some of us will have to forego feeling special, if we want to be critical of what is set up to be the truth. The optometrist that diagnosed my son used to do work for the military. During the Vietnam war people who were colour “blind” were recruited to review the aerial maps of jungle areas to detect “disturbances” in the green terrain that proved to be evidence of enemy activity. This was very successful until the opposition went underground…I can’t comment any further on the science, because it’s just not my field, but it’s encouraging to see this kind of dialogue here…especially for a father who is interested in science that makes a worthy difference I his son’s life. But alas there will be times, when we may all fall victim to the deceptive words of those fucking nueromarketers in the glossy pages of FB read in the waiting room of their local doctor’s office, waiting for a flu shot.. 😉

  9. Mojca says:

    I really like this article, because is scientifically grounded yet very readable and simple to understand. I have come across the term of tetrachromacy yesterday and it really amazes me … I believe in the science here, that it is very rare, at least in the population which has been tested for. For me, it is just the prove that ‘the magic’ really exists … in the sense of tetrachromacy, what is magical is the perception of the reality that our body is allowing us … is so much wider than normal, that normal cannot believe in it because for it, it doesnt exist! I can really see how these women with the functional four cone cell were seen as crazy and delusional through the history … however rare they were. And it comes to my mind the quote ‘and those who were seen dancing were thought to be insane by those who could not hear the music’ …. And I am just wondering how many different mutations there are in different bodies, and how astonishing fact it is, that our body, our senses, are truly our window to reality … So please, always believe in magic, because what is magic for someone, it just might be the reality for somebody else! 🙂 🙂 (and off course, there is also those who feed their egos by being magical all the time, but I am not referring to social disfunctionality here but more to genetic abilities ans social inclusion of differences…) ..

  10. Jessamina says:

    Great article, I’m still intrigued by the subject, so will continue my search down the rabbit hole..I have recently seen an exquisite 360 degree google image of an ancient Temple of Hathor in Egypt. Eons of soot were cleaned off the ceiling to reveal blue the sky. I know you had mentioned it was called “golden” in ancient and biblical times. Interestingly, when I first saw this image there was something magical in that color…it was golden. You can go to google map/temple of Hathor at Dendera Egypt and then just get a live view, close as possible with the little man for the street view Enjoy! maybe we are all capable of tetracromancy
    …Here check it out,32.6703752,3a,75y,4.57h,167.06t/data=!3m8!1e1!3m6!1s-fJwyoDBFlC4%2FVm3jFFUtwUI%2FAAAAAAAAQEE%2FVNgd9lKnKvQAUA_IXJQNuzTrDJMnfgFtgCJkC!2e4!3e11!!7i8704!8i4352!4m13!1m7!3m6!1s0x0:0x55c5acd6d797167f!2sTemple+of+The+Goddess+Hathor+(Dendera)!3b1!8m2!3d26.1419501!4d32.670242!3m4!1s0x0:0x55c5acd6d797167f!8m2!3d26.1419501!4d32.670242

  11. So how do you explain that I see 39 colors as well as my father does, but both my sister and mother see less colors even less than 20? Does it mean they are color blind? I do undesrtand all your arguments and agree with them but I have the doubt about on why some people see less or more colors than the others.

  12. Lala says:

    I took all types of test that said I was tetrachromat and despite defeating each one I was always thinking the words “horse shyt”. Mainly because like you said, my monitor can only have 3 shades of colors at various degrees creating the illusion of color. And the fact that color does not exist, color is created in the brain and used as our brain’s way of labeling each wavelength of light, for example, Pink does not exist in the real world at all, there is no color wheel. Our brains made up pink to connect red and purple. Pretty much it was our brains way of completing our color definition range. Light is light until the brain makes it something else, our brain knows when different wavelengths of light are entering the eyes when the cons in the eyes fire up and tell the brain…. thing is color is just labeling the many different various patterns between the cones. So yes even if you had more cones it would not change much sense the brain still uses the same colors to code each wavelength.

  13. Ivan Z says:

    Your title is misleading, you admitted there are tetrachromats. Also, one Jay Neitz, a color vision researcher at the Medical College of Wisconsin, estimates that half of the female population has a fourth cone in their eyes, and even 8% of men (three cone genes on the X chromosome, on top of the one on the seventh chromosone). There are more ways in which this is possible, than sone pll think.

  14. Carmen Robinson says:

    Long before computers were in homes and most businesses back in the early 80s, I worked in a photo processing lab. We had to do a color test using either chips or paper (I don’t remember), but I scored a “0”! I was told then that I was one of the few people in the country who scored that low, which is the best score you can get. So, I’m not sure where you got your data because I also took the computer test tonight and scored “0” again! I am a true tetrachromat!

    • DangerOnion says:

      If you took the test on a computer, then it can’t prove you’re a tetrachromat for reasons that I explained exhaustively in the post. And I don’t know what test you took in the 80s, but it was probably testing standard color vision, since tetrachromacy is so rare that it would be pointless to even look for it.

      • Carmen Robinson says:

        The test was just like the computer test… the color chips had to be arranged by shades and tints just like the computer test.

  15. d euto rite says:

    Only two women empirically proven to be tetrachromats. How do they view the night sky, a rainbow, a forest (temperate or tropical)? I’ve used the color blindness filters for my camera, and the trichromatic algorithm is so much brighter than the dichros’. Three to four might only be a bit more colorful, based on Pascal numbers, and fractals, and, how, it occurs, rarely, but isn’t always detected. It’s mutations like these that can sometimes have an advantageous effect for a race of animals, but only when the advantage is necessary to survival, does it become desirable, and thus, shape evolution. We homosapiens can keep ourselves alive out in the elements, day to day life, just fine with three or less color receptors, it’s the depths and shapes that we need to move around. Colors are a luxury!

  16. tomcat1116 says:

    This is even more funny if you consider that Diana Derval’s original image actually has over 10,000 distinct colors. That’s what happens when you don’t know what you’re doing and don’t understand what image compression does to images. Next time try GIF format or lossless PNG Diana!

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