YOU ARE NOT A TETRACHROMAT, AND THIS GRAPHIC IS BULLSHIT

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.]

162 thoughts on “YOU ARE NOT A TETRACHROMAT, AND THIS GRAPHIC IS BULLSHIT

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    1. Great article. Love the eloquent use of profanities to pitch the argument. Curious if author would be interested in republishing for a “G” rated audience? I would love to get the word out to a more conservative circle. If not I look forward to more good myth busting.

      1. People without a corneea reported to see UV as blue/indigo-white, as their eyelens doesn’t filter UV out anymore. So it’s not an absolute thing, but for the most, UV is not accessible.

  1. Great work! It’s worth mentioning the tetrachromatic nature of mesopic vision, though; in low-light situations, the activations of rods and cones can be roughly equal. Rods are most excited by wavelengths between those of M and S cones, so they add further depth to color perception.

    1. That did come up in my research, but it’s a pretty specialized situation. Plus it doesn’t apply to the main claim that you can diagnose tetrachromacy with a graphic online. Thanks though!

      1. The article leaves a disclaimer saying that it is not a diagnosis, so technically it doesn’t claim that you can diagnose tetrachromacy with a graphic from the internet. That’s not to say I don’t agree that the article is wrong; it has loads of misinformation, but you should check your own claims before posting them.

    1. That has nothing to do with depth perception. You are still looking at a flat, 2D surface in the video. A better comparison would be covering up one of the LEDs on your head to see if the wii-mote will still be able to properly pick up your position in relative to it. (which it wouldnt be able to) 😉

  2. Right there with you until the last paragraph. It’s been demonstrably proven that humans do not need two eyes for depth perception, and indeed, there are humans with a genetic deficiency with two functional eyes — who nevertheless do not perceive depth.

    1. It’s true that depth blindness is an observed phenomenon, but depth perception with only one eye (from a static position) is geometrically impossible. Parallax is required to gauge distance in a truly alien environment. The brain can “learn” depth perception with only one eye based on the perspective allowed by straight lines on roads and buildings and the relative sizes of objects whose true size the brain already knows, like people and cars. Put a one-eyed person in a featureless void, however, and then put a visible sphere in front of them, and without physically moving their head there would be no way of determining its distance. The quasi-depth perception afforded by perspective is good enough for most of everyday life, but it’s not the same as the true depth perception offered by binocular vision.

      1. Very nice piece. Just minor quibble here. As you note, binocular disparity and motion parallax are important cues to depth, and pictorial depth cues, like relative size and linear perspective are often not as compelling as motion. But there are also a few other monocular depth cues that you have missed, besides motion and pictorial depth cues. They are sometimes called oculomotor depth cues, based on the muscle movements of the eyes. The first, convergence, is how the eyes rotate inward towards each other when objects get closer. Even with one eye closed, the angle of rotation of the eyes would be a cue to depth. The second is accommodation. When your lens gets thinner or fatter to help focus on an object, the muscles which accomplish that give us a cue to how far away that object is. So, in a completely dark room with a visible sphere, up to a certain distance we can tell how far away the sphere is.
        Anyways, thanks for indulging my extended pedantry. Really enjoyed the piece. Especially die in a multicolored fire.

      2. Good points. I’m not sure how convergence would help, since it’s reliant on the position of the head — if my left eye is rotating inward to focus and I rotate my head to compensate, then the left eye will still be pointing forward rather than inward. The flexing of the lens is something that had occurred to me though.

      3. Television is the clearest example of that binocular vision doing you no good. The vision projected is with a single lens, illuminated against a flat screen, and yet, you are still able to perceive depth in the image.

      4. I have been blind in one eye since shortly after birth. I have absolutely no depth perception. Static or not makes no difference. If someone is standing in front of me holding out a glass of water to me I can’t tell how far away it is even if I move my head or walk to the side.

  3. Good work! Color science is a complex field, and the subjective nature of human perception makes color even more difficult to understand and describe. I designed a color-calibration device some time ago and have been working to get multiprimary sensors and displays into wider use, but it’s difficult to get people to understand that most cameras and displays only work with about half the range of colors that the human visual system can distinguish. I hope your post raises awareness of the opportunity for better solutions.

    . png

      1. Just for the record, I had the initials first. And I was using them in my .sig file long before the PNG format was invented. Actually it’s only the residents of Papua New Guinea who could rightfully complain about me stepping on their toes.

  4. The part where he talks about chromosomes is simply not true, though.
    “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.”
    That’s not how colour-blindness works. Color blindness is on the X chromosome only, but is recessive. This is why women have a lower chance of it. As long as they have one good X chromosome, it will allow them to see colours normally. It has nothing to do with having four sets of cells and having one disabled. Mothers of colour-blind men must be carriers.

    1. Color blindness isn’t only on the X chromosome, actually. According to the Online Mendelian Inheritance in Man (OMIM) database at Johns Hopkins University, mutations capable of causing color blindness originate from at least 19 different chromosomes and 56 different genes. From a Caltech study, “In humans, two cone cell pigment genes are on the sex X chromosome, the classical type 2 opsin genes OPN1MW and OPN1MW2. It has been suggested that as women have two different X chromosomes in their cells, some of them could be carrying some variant cone cell pigments, thereby possibly being born as full tetrachromats and having four simultaneously functioning kinds of cone cells, each type with a specific pattern of responsiveness to different wavelengths of light in the range of the visible spectrum.” The full study is here, if you’re interested.

    2. My ex wife is red/green colour blind (_very_ unusual, I know), but neither of her sons or her daughter are. So if the colour-blindness gene is _only_ on the X chromosome, then my step-daughter should also be colour-blind, unless there’s something on the Y chromosome that counters it.

      Or colour-blindness is affected by more than just the genes on the X chromosome.

      1. I understand where you are going with that, but unless your step daughter has Kleinfelter’s (a genetic disorder that causes a person to have two X chromosomes and one Y chromosome), in which case she would be biologically male, the Y chromosome would not have any affect on her or the X-linked RECESSIVE gene of red-green colour blindness. And just because the mother was colour blind does not mean the daughter will be because she would have to have inherited the recessive gene through the X chromosome received from her biological father. That being said, any of your step daughter’s sons (when she has any since I do not know her age) have a 50% chance of not being red-green colour blind since she is a carrier for the gene.

  5. Color information is sent to the brain via two channels, not three. One channel is for red/green processing and one channel is for yellow/blue processing. Also, light itself is not colored. It is only made up of packets of energy traveling at various wavelengths. Isaac Newton made this distinction in 17th century.

    1. Firstly, the use of the word “channels” to describe the transmission of the three sets of cones to the brain is widespread. The University of Illinois’ “Color Glossary” defines trichromacy as the “condition of possessing three independent channels for conveying color information, derived from the three different cone types.”

      Secondly, you have been egregiously misinformed about the discovery of the photon. I am well aware that color is a result of the various wavelengths of light, though to say that “light is not colored” is a bit of an oversimplification, as there is no physical distinction between the color of an object and the wavelength of the light it emits or reflects. They’re the same thing. Isaac Newton, unfortunately, knew none of this. The “quantized” nature of light was first hypothesized by Albert Einstein in the early 20th century and demonstrated conclusively by Arthur Compton’s Nobel-winning scattering experiments in 1923, nearly 300 years after Newton’s death.

      1. “For the rays, to speak properly, are not coloured. In them is nothing else than a certain power and disposition to stir up a sensation of this or that Colour” Isaac Newton (1730).

        As far as color channels to the brain go, there are two stages to color vision processing in the brain, one at the level of the cones which is trichromatic (the three cone types) and one which is color opponent, which creates two channels for color, again one red/green and one yellow/blue. The trichromatic theory of color vision and opponent process theory competed for years in the history of color science but there is a great deal of physiological evidence today (from the 1950’s and 1960’s) to support both. It depends on whether you are looking only at the cones or processing further along in the retinal ganglion cells, lateral geniculate nucleus, and striate cortex.

      2. Well, color is a perception, not a property of physical objects. So, light itself is not colored. Cynthia’s comment below is an accurate account of the distinction between trichromacy and opponency, both of which allow us to see color as we do. Finally, I felt my brain was suffocated with stupidity after reading the erroneous infographic. Thank you for taking the time to write this response. May they burn in a multicolored fire indeed.

    2. Well …

      First of all, color is how we describe our sense of light wavelengths, especially combinations of same. That is, our sense of light spectra.

      Those spectra occur in various other contexts than light striking the eye, and thus it is fairly common to describe those also using the word color.

      Among those contexts is the spectrum of any subset of photons, and the absorption and reflection spectra of surfaces and more-or-less transparent substances (and of course the emission spectra both from black body radiation, and from specific sets of lines as in LEDs or bio-luminescence).

      We do that because it is more useful to say “this is a red LED” or “this is a red flower” or “this piece of metal is glowing red because it is so hot” than it is saying “the light this LED emits will be perceived as red when it hits a human eye” and so on.

      Also, it is good to remember that, for example, red cones do not simply sense “red” light. They do in fact sense a broad spectrum of light, it is just that their reaction to red light is strongest. Most frequencies in the visible spectrum (which is, interestingly enough, pretty much exactly one octave worth of frequencies) actually activate all three cone types, just in rather different amounts.

      Which suggests how even colourblind people might learn to recognize a few differences in colour they shouldn’t naively be able to. I don’t know if that actually happens. It doesn’t change the fact that their color perception is one dimension smaller, just the way that works out in detail.

      Another thing is that I remember learning, not so long ago, that our current color perception is actually a consequence of genes for one color (duplicating and one set) mutating, and it seems that tetrachromates have the same genes doing that again.

      Also, color in language also seems to have started out rather simplistic (white, black, red(!)), and even today languages differ fairly drastically in color treatment – I seem to recall that one language on the British islands (maybe Irish?) actually used the same word for green and blue, for example. (Obviously, this ignores the modern tendency of inventing lots of different names for subtle shades by appropriating existing words for other things, sometimes badly as I remember from a recent discussion on “lime”, which a picture search for the color easily confirmed).

      1. Not Irish. The word for green in Irish is glas, and the word for blue is gorm. The Irish term for pink however, is bándearg, which means whitepink

  6. 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

    Monet had lenses for most of his life; we know because he developed bad cataracts (and painted everything yellow/red tinged, because the lenses were filtering out all the blue wavelengths). He underwent cataract surgery in his 80s and OMG EVERYTHING’S SO BLUE.

    http://www.uic.edu/depts/vpl/teaching/Werner%20-%201998%20-%20Chapter%20about%20Monet.pdf

  7. In 2007, one of the researchers tried a different technique.

    I can see you’ve read Mollon’s and Jordan’s work (another tetrachromacy researcher is Kimberly Jameson).

    Now there is still the possibility that what their tetrachromat is seeing when she looks at the red + green mixed-wavelength light is a kind of “grainyness”, from the mosaic of cone cells in her retinas.
    That is, some of her cone cells are M, doing ordinary M-cell things; some are ordinary L; but others are L’, with their peak sensitivity somewhere between L and M. Which ones are L, and which are L’, depend on which of the two X-chromosomes in each cell is working — one or other of the X-chromosomes is switched off during fetal development. And there’s a ‘clumpiness’ of the L and L’ distribution… areas of M-cells and L-cells; other areas of M and L’ cells.
    So in one area, the signals from M and L cells get compared, and a message is sent up the optic nerve saying, essentially, “That’s yellow”. Meanwhile in an adjacent area, the signals from M and L’ cells are compared, and because the L’ has a different frequency response, the signal up the optic nerve is “That’s a different shade of yellow”.
    Meanwhile, for the monochromatic-yellow light, the results of the M-L and M-L’ comparisons are different. So in the end, Jordan’s tetrachromat could be looking at the red+green “yellow” disk and seeing a mottled effect, distinguishing it from the single-wavelength disk.

    I hope that makes sense.

  8. Almost unrelated point: Your digital camera generally detects UV; looking at a TV remote through it and pushing buttons produces a bright white light. I learned this as a trick for seeing whether a UV emitter is broken or not in a lab that had a lot of broken ones.

    1. Thanks for pointing that out. It’s true that a digital camera detects light outside the visible spectrum (though I believe TV remotes work in IR, not UV). However, in the vast majority of cameras, the image is saved as a JPEG and is thus sorted into RGB colors.

    2. Remote controls use IR, surely. UV LEDs exist, they are found in some flashlights, but I’m not aware that they’re used in remotes.

      1. Yes… the CCD sensors are actually far more sensitive in the red end of the spectrum than your eyes, and that´s why you can see the lights in the remote controls using a webcam or a photographic camera. It would not work equally well in the UV, because —I am not checking the numbers but I seem to remember this– the atmospheric UV cut is actually extremely close to our own sensitivity cutoff. There would not be much spectral room for the remotes to emit and reach their destination without us seeing blue light everywhere!

  9. And to top it all off, her color bar image is a heavily compressed JPEG that, as a result, no longer even represents the colors that were presumably intended.

    Most bars have additional banding within them, and some bars have more variation within them than compared to their neighbors. Some neighboring pairs are identical at the boundary, but it’s unclear if that is a deliberate ploy of the “test” or not.

    But aside from the physical color representation of the image, the comments on her own post debunk Derval’s claims. The kicker should be that she asserts anyone who sees more that 33 colors is a tetrachromat, yet virtually everyone who bothered to comment counted more than 33 — both male and female. By her own claims, no more than 25% of people should see that many; and the genetic basis of potential tetrachromacy tells us that all of them would have to be women.

    That any men at all “passed” her tetrachromacy test invalidates it as a test.

  10. Thank you! I immediately googled a debunk after reading the article and it felt so good to read some sense.

  11. Brilliant!

    My favorite part about this article is the unrelenting “you’re an idiot for believing it.” Computer screens are created by human beings catering to the largest human demographic, trichromats. Therefore, an image that potentially shows a fourth “color” canNOT be displayed on a screen created by/for humans. Not even for superman.

    But that is only one (and by far the simplest) of the facts that you thoroughly explained with researchable facts.

  12. As a graphic designer with over 2 decades of experience, I (and many of my collegues) have trained ourselves to differentiate color on a very fine scale. I know people who can look at any object, and tell you what PMS color it is, and usually be right.

    I often get frustrated with clients (and family members) who don’t have this ability/skillset. It is sometimes difficult to remember that most people simply don’t see colors like I do. I can’t number the arguments I’ve had with my wife over colors that “don’t match”, which are painfully obvious to me, but she swears there are ABSOLUTELY no difference between them.

    You can believe what you want. Your reality tunnel is largely defined by biology, and you can’t help that. But saying that your reality tunnel is the ONLY accurate way of seeing the world, and that anyone who claims to see more than you is delusional is patently absurd…

    BTW, I see 37 colors in that graphic. I think the one I’m missing in in the light violet bar, and bright yellow colors DO drive me up a wall…

    1. The author isn’t claiming that everyone can perceive or distinguish exactly the same colors – rather, that the physiological explanation in the LinkedIn article is bogus for several reasons.

      The natural sensitivity of your trichromatic visual system plus years of training have enhanced your ability to see extremely fine distinctions between the colors in the normal human visual spectrum. The fact that a highly trained designer such as yourself can “only” perceive 37 of the 39 colors in the image supports one of the author’s points: a JPG on a trichromatic RGB screen cannot be used to identify tetrachromats.

  13. Aphakia is not “seeing in UV”. Aphakia is defined as “absence of the normal lens” and pseudophakia “false lens” is the result of present day cataract surgery techniques whereby the normal but clouded lens is removed and an artificial lens is substituted. These artificial lenses have UV filters built in to prevent damage to the macula which is the area of the retina responsible for fine focusing.
    Please don’t confuse these terms anymore than the media has already.

  14. “Nothing says legitimate scientific knowledge like a winky face with its tongue out.” What does a whole lot of foul language in an article say about a person?

  15. I have a brown right eye that saw 44 colors, and a left green eye that saw 46 colors. The green eye could distinguish the yellows, where the brown eye could not.

  16. This article (for lack of proper terminology), is as full of holes as the original. Go back, research further, come back when you have a better grasp of the information. Oh, and please un-ass your writing style, you sound like a student from a state university who thinks he knows what he is talking about and wantseveryone else to think the same

  17. So, I am a woman who perceives some certain shades of blue and green as textured grays, but I can see most of them just fine. My maternal grandfather and maternal uncle share the same trait. Can anyone out there give me some idea as to what might cause this?
    While being treated for an unrelated eye condition, I described this phenomenon to several neuro-ophthalmologists and my strabismus surgeon. None of them could really give me any answers, other than assuring me that I had passed the standard red/green color blindness test.
    It doesn’t concern me, really. I’d just like to be able to put a label of some kind on the family trait. Thanks!

  18. Having seen the original graphic on Truth Theory, I came to the conclusion before I even came across your article that it was catastrophically flawed (and proved my suspicion that Truth Theory will post any rubbish it likes).

    Then I came across this. You make some excellent points … but your article is flawed and badly written…

    First of all, your dismissal of Diana Derval’s job title shows that you haven’t bothered to so much as research neuromarketing. It is, in fact, “a new field of market research that studies the cognitive, affective and sensorimotor response of adverts and marketing material”:
    http://en.wikipedia.org/wiki/Neuromarketing

    It is, perhaps, unorthodox and there are a lot of blogs etc which question the effectiveness of neuromarketing, but it is a genuine field of study, and, frankly, it was incredibly rude of you to dismiss it out of hand so easily and so publicly. A simple, 2 second Google would have enlightened you. It does you no favours and shows you up as ignorant.

    Secondly: The frequent use of expletives throughout your article suggests a limited vocabulary and does nothing for the credence of the article itself.

    Thirdly, the very fact that you have been forced to edit your article THREE times, each time contradicted parts of your own article, suggests that you hurried through your research and didn’t take the time to research thoroughly and come up with ALL the facts, highlighted further by the fact that you only edited the article after you received contradictory comments.

    Next: Lack of sources. Not once, in your article have you supplied any material or links to further reading which “back up” the point/s you’re trying to make, unlike some of those comments previously mentioned.

    And finally … What on Earth has a gif of a cat and a horse got to do with this article? Serious readers won’t be put off by the amount of reading if it’s well written, accurate and educational.

    I second Doc Jock above: Go back to the drawing board, research further, read a few books to increase your vocabulary and then come back with a better written, less offensive article that actually proves that you know what you’re talking about.

  19. I very rarely comment on sites like this, but as a person who Google/Snopes searches every forwarded article I get, thank you for such a through debunking of such a ridiculous post. Just like the original blue/gold dress thing – whoever that now they’re getting an accurate test of their color acumen on a little phone screen is an idiot.

  20. There is depth from focus/defocus. To tests it, if you have two functioning eyes, close one of them and move one eye around focusing on the different things on the room. You will
    perceive the depth difference.

  21. Thank you for this!
    Funny enough I have heard about tetrachromacy on a german detective audio drama. So I researched it a bit. And today it was the first time I came across that post with the colour graphic on someone’s time line. So thanks for doing this post and explaining it all for me, hahahaha!

  22. “probably more common in women of Northern European ancestry”

    Is this from one of the studies you read? Or just your own conjecture? I’m curious since I’ve been scrounging scholar.google.com and Google search and haven’t found anything.

    If you read it from a study, can you post a link to it? Thanks.

    1. It’s definitely from a study, but I can’t find it for the life of me. If I recall, it’s something to do with the fact that Northern Europeans (white people, to be honest) tend to be more genetically heterogeneous, especially when it comes to eye color, and so the mutations that lead to non-functional tetrachromacy happen more frequently. That same population has more colorblindness for the same reason.

  23. Correct me if me or my television is wrong, but in the color chart near the top…there is like over 60 shades of colors haha one problem I’ve noticed is if you take to long inspecting a certain set, some colors may bleed out of your vision.

  24. This is a wonderful antidote to those horrible online tests. I have taken the DNA test for tetrachromacy and do have the genetic basis and a lot of the behaviors. I will go for further testing, as well, to see just how functional it is. Thank you for your work.

  25. My eye doctor does in fact think I may be a tetrachromat. I can see what my art teacher describes as “too many colors,” and tell very minute differences between colors, to the point of sometimes seeing brushstrokes on painted walls that I have been assured don’t exist. Light is never just white, and almost all optical illusions (especially those relying on color) do not work on me at all. I would be very curious to get tested formally, though I am not sure how to go about that.

  26. I count about 190 colors in the chart.

    Give or take a few. I was counting pretty quickly.

    ( Additionally, not every single line of colored pixels is one color vertically. I did not count the variations within single vertical lines except when they were very dramatically different. So probably MUCH more than 190 but yeah.)

    1. Entirely a feature of JPEG artifacting, I’m afraid. The original image contains only 44 vertical bands of uniform color, but the way that color spectra are compressed by the JPEG format adds variation where none should exist.

      1. Naturally. I’ve understood img data distortion since I was extremely young (long story).

        Even still. You simply can NOT honestly tell me that there are less than 30 colors within just this one section of the above graphic which is zoomed in as far as MS Paint will let me, saved in png format copypasta of full-size original image thus any color noise distortion would carry over but not become further aggravated):

        https://drive.google.com/file/d/0B1xDzl7M4LJ7OWwyTjZPUlMzVkE/view?usp=sharing

        I can distinguish what I guess “most” people would see, which is about 30 colors within that section?; however, counting all the variations I see, I arrived at over 80 before I was completely through the brightest, most vibrant “pink” section (before I was pulled away from my computer, as I am at work). I’m also not on my 1080p led calibrated monitor this time which I’d think would make it easier, except this screen is glossy unlike my 27″ so I was also attempting to account for that in my count. My original count was not zoomed in at all and it is clear to me that there are hundreds and hundreds more shades to be distinguished when zoomed in as far as possible. Now it is absolutely likely that some of these shades couple be extremely similar if not the same, but are simply placed nonadjacent within the graphic, but I’d have to pull the image apart pixel by pixel to determine that precisely.

        When I say vertical lines, the VAST majority of unique colors I perceive are not in bands but in lines that are one or two pixels wide, with the exception of only two MAYBE three “bands” that are three to five pixels wide. And within many of these vertical lines I also perceive variations in levels, tone, saturation, hue depth, undertone, overtone, cool or warm, etc.

        Using the linked image cut-out section above as an example; starting about four or five pixels inward from the left, the undertone of this particular purple has MUCH more of a hot magenta base, as if said magenta-ish base is neutral but with a muted, somewhat watered-down grape-gray overtone washed atop of it with, say, maybe about 60% opacity? Whereas the two shades immediately to either side of this one, while not the same, are both a bit more cool-toned but, more than anything, very distinctly lack that magenta-ish value. Sort of like how you can get different shades of purples by mixing different types of reds and blues. Quin violet and ultramarine make a more royal shade of grape-ish purple, whereas maroon and indigo make a more muted, almost gray-leaning foggy purplish tone with a medium hint of grape shade. (See: https://tabascocatart.files.wordpress.com/2013/02/purples-2.jpg for img I’m basing these two mix descriptions from. Img not mine, though I do enjoy painting with watercolors quite a lot.)

      2. WOW. I thought the fades were there so I could count the breaks and determine what I already knew… I have a superior sense of color and catching slight reflections/color nuances out of the corner of my eye.
        I see defects in my house painters work LONG before they do, even when Im pointing it out!!! LOL
        BTW The blue and black dress also comes in white and gold. There was only one photo that looked kinda like both and the rest were just side by sides of the same style dress in its different color options. Oh how the rumor mill grinds a story.

  27. Oh my goodness! Impressive article dude! Thank you, However I am going through problems with your RSS.

    I don’t know why I cannot subscribe to it. Is ther
    anyone else getting identical RSS issues? Anyone that knows the answer
    can you kindly respond? Thanx!!

  28. This was actually really interesting to read. Love when mysteries like this are bustes especially because even though it is nigh to rare, we know it exists, which means there will always be phonies :D. Wish in the future though we could develop something that could test for tetrachromacy, if it was possible.

  29. The reason I find myself on this site is because I see many images on paintings that no one else sees…or at least admits to. The paintings I concentrate on are Impressionist’s…and the styles that evolved from those into the 20th Century. Most will tell me I’m delusional. I’m not. I’m wondering if it has anything to do with any vision conditions I might have. I am color blind…what type…I have no idea. I just know I can’t see the numbers in the color charts. I can see things in paintings no one else can see but I can’t see any freaking numbers! It would take much too long to elaborate but what I see is 2 grizzly crimes…involving one of the most well known artists of all time. Ya know? Forget what the images are…I just wanted to know if anyone might have a clue why I see this stuff “almost” no one does. I do believe there are people who know about it and have gone to great lengths to hide…including physically vandalizing the images. I have a pretty good idea what those of you who read this are thinking. I don’t blame you. So…anyone got any idea what could be going on here. Besides “delusional” crap? I feel like the kid who seen “dead people”.

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