9 ms·

A tiny group of people can see ‘invisible’ colours that no-one else can perceive

194 points by austinz 12y ago

joelthelion 12y ago
It's not that they see a few colors that no one perceives, it's that for them color is a 4 dimensional space instead of a 3 dimensional one. So it's a whole new world of different colors.
- Houshalter 12y ago
  Even though our eyes detect color in 3 dimensional space, that doesn't seem to be how we perceive it. E.g. I can't tell you how much red, green, or blue is in a color, just that it's close to the cluster of colors I recognize as "purple" or "blue" or "orange" or whatever. See this chart for example: http://imgs.xkcd.com/blag/satfaces_map_1024.png http://imgs.xkcd.com/blag/satfaces_map_1024.png Interestingly there is some evidence that culture and language might affect our perception of color.
  - jacobolus 12y ago
    You are incorrect about that, and Randall’s drawing is misleading you (it shows the gamut boundary of an RGB cube, rather than the full three-dimensional color space he asked about in his survey). For people with “normal” trichromatic color vision, the color we perceive when looking at a particular spot does indeed fall into a three dimensional “color space”. You’re right that without careful attention/training it’s hard to state colors in terms of coordinates in terms of cone cell responses directly or color opponent signals (blue–yellow, red–green, white–black). It’s easy to train someone to give reasonably accurate color coordinates in terms of lightness, hue, and chroma, however. If you want to understand human color vision in detail, I recommend this online resource: http://www.handprint.com/LS/CVS/color.html http://www.handprint.com/LS/CVS/color.html
  - amitp 12y ago
    We seem to perceive it in something closer to hsl space (3d) than rgb space (also 3d). You can tell that it's "purple" but you can also tell whether it's saturated or not, and if it's bright or dark purple. Also check out Lab space: http://en.wikipedia.org/wiki/Lab_color_space http://en.wikipedia.org/wiki/Lab_color_space
  - canjobear 12y ago
    > Interestingly there is some evidence that culture and language might affect our perception of color. The evidence for effects of language on color perception is very weak, or it indicates that the effects are themselves very weak. The big paper in this field is this: http://www.languagescience.umd.edu/~ellenlau/courses/ling440/Winawer_2007.pdf http://www.languagescience.umd.edu/~ellenlau/courses/ling440... They find that Russian speakers, who have separate words for two shades of blue, can discriminate between those shades of blue something like 50 ms faster than they can discriminate between two shades of blue that fall into the same color word category. First thing to note, that's a very small difference. Second thing: the effect goes away under verbal interference (like when you have the subjects repeat a word over and over again while doing the color discrimination task). So I guess there's an effect of language on color perception, but not while you're talking? It definitely doesn't seem to me that the colors I am perceiving change when I am talking vs. when I am not. Third, there's a huge overall reaction time difference between the Russian and English speakers in the paper, which calls into question how well the experiment was really run. So it's not clear that there really are effects of culture/language on color perception; and if they do exist they are very small. (At least that's the conclusion I would draw from this paper, which is widely cited in that field. I'd be interested to hear of different results if they're out there.)
shutupalready 12y ago
> Jordan’s “acid test” involved coloured discs showing different mixtures of pigment, such as a green made of yellow and blue. The mixtures were too subtle for most people to notice: almost all people would see the same shade of olive green, but each combination should give out a subtly different spectrum of light that would be perceptible to someone with a fourth cone. From what I understand, a modern monitor is capable of displaying the entire range of colors perceptible to the human eye. Am I mistaken about that? So would it not be possible to create a web-based version of these "coloured discs", and then we can test ourselves.
- sigterm 12y ago
  > Am I mistaken about that? Yes. See: https://en.wikipedia.org/wiki/Gamut https://en.wikipedia.org/wiki/Gamut
- TheSpiceIsLife 12y ago
  Google 'tetrachromacy test', first hit http://www.blogadilla.com/2008/06/08/are-you-a-tetrachromat/ http://www.blogadilla.com/2008/06/08/are-you-a-tetrachromat/
  - sigterm 12y ago
    that claim is quite dubious. I don't think it's possible to create metamers for people with normal 3-color vision on an RGB monitor. To do that you need an extra degree of freedom. https://en.wikipedia.org/wiki/Metamerism_(color) https://en.wikipedia.org/wiki/Metamerism_(color)
    - Xcelerate 12y ago
      Hmm... I'm not sure about that. It's an interesting question. It's equivalent to the question: can we create two images on a computer monitor that appear the same to a person with normal color vision yet appear different to a colorblind person? I think it would depend on the particular mapping from 3 to 2 dimensions... it might be possible.
Kiro 12y ago
Am I the only one who thinks her painting of the tree looks the same as the photo color wise?
oska 12y ago
I'm from Australia but hadn't heard of the Rainbow Eucalypt before (the tree that the featured tetrachromat painted). That's not so unlikely as there are a lot of Eucalyptus species. Still, I was curious and so looked it up and was very interested to find that it is a Eucalypt from outside Australia and, more than that, the only one whose native region partly lies within the northern hemisphere. Another name for it is the Mindanao gum, as it is native to the tropical rainforests of Mindanao in the Philippines (north of the equator). http://en.wikipedia.org/wiki/Eucalyptus_deglupta http://en.wikipedia.org/wiki/Eucalyptus_deglupta
philh 12y ago
> The crux of Jordan’s argument lay in the fact that the gene for our red and green cone types lies on the X chromosome. Since women have two X chromosomes, they could potentially carry two different versions of the gene, each encoding for a cone that is sensitive to slightly different parts of the spectrum. In addition to the other two, unaffected cones, they would therefore have four in total – making them a “tetrachromat”. Why couln't this happen for either of the other cones?
- jacobolus 12y ago
  The gene for the “short” wavelength cone† is located on chromosome 7, whereas the genes for the others are located on the X chromosome. Since females have two X chromosomes, it is possible for them to have 2 variant copies of the long or medium cone genes. (Since males only have one X chromosome, color vision deficiencies caused by a missing or abnormal copy of one of the medium/long cone pigment genes are much more common than for females.) It would certainly be possible for a genetic mutation to result in an extra mutated copy of the short cone pigment gene, but I don’t think I’ve heard of variants of this gene with slightly different light sensitivity than the usual type (they might exist though?). By contrast “non-standard” version of the medium cone pigment gene is relatively common. See: http://ghr.nlm.nih.gov/gene/OPN1SW http://ghr.nlm.nih.gov/gene/OPN1SW http://ghr.nlm.nih.gov/gene/OPN1MW http://ghr.nlm.nih.gov/gene/OPN1MW http://ghr.nlm.nih.gov/gene/OPN1MW2 http://ghr.nlm.nih.gov/gene/OPN1MW2 http://ghr.nlm.nih.gov/gene/OPN1LW http://ghr.nlm.nih.gov/gene/OPN1LW † We should properly refer to the cones as long, medium, and short rather than red, green, and blue, since color is computed from differences in cone responses.
- gus_massa 12y ago
  The male equivalent is "Anomalous trichromacy" http://en.wikipedia.org/wiki/Color_blindness#Anomalous_trichromacy http://en.wikipedia.org/wiki/Color_blindness#Anomalous_trich.... You have one of the color receptors tuned to a slightly different frequency, so you see the word in a different way. (Which way is the correct way?) This condition is easy to spot with the standard Ishihara color test, so it's easy to measure the % of the population in these cases. --- Green The most common case of male anomalous trichromacy is the "wrong/unusual" green receptor case, so the most common case of woman tetracromat is one that has 2 copies of the usual blue receptor, 2 copies of the usual red receptor and 1 copy of the usual green receptor 1 copy of the unusual green receptor. This is the case discussed in the article. To reduce the text size I'll denote this kind of tetracromat with BBGgRR, where the capital letter denote the usual color receptor and the noncapital letter denote the unusual color receptor. (This is unrelated to recessive and dominant genes that are usually denoted by capital and noncapital letters.) --- Red The second most common case of male anomalous trichromacy is the "wrong/unusual" red receptor case, so the seccond most common case of woman tetracromat is BBGGRr (1 copy of the usual red receptor an 1 copy of the unusual red receptor). Obviously, you can have both mixed copies, so a woman can have BBGgRr and be a pentacromat. At least have the genes to "see" in a 5-dimensional color space. If she can use this ability is less clear. --- Blue The least common case of male anomalous trichromacy is the "wrong/unusual" blue receptor case, so the least common case of woman tetracromat is BbGGRR. It can be mixed with the other cases, so a woman can be pentacromat or hexacromat. The interesting part is that the blue gene is not in the X chromosome, so both male and females have two copies. So a male can be tetracromat BbG_R_ . But this chromosome is not inactivated as the 50% of the X chromosomes in females. So I'm not sure if it's possible to have a different kind of vision in this case. --- It's more complicated Actually you can have more than 1 copy of the color genes in each chromosome, and there are more than two variations of each gene, so it's more complicated.
jimmytidey 12y ago
Mantis Shrimps have 12 photoreceptors, they can also see in all polarisations. They don't do paintings so it's hard to know how they experience this. http://en.wikipedia.org/wiki/Mantis_shrimp#Eyes http://en.wikipedia.org/wiki/Mantis_shrimp#Eyes
Schiphol 12y ago
Antico's painting of an eucalyptus doesn't "give us a hint of the extra shades she is seeing". It's just another instance of the [El Greco fallacy](http://www.huffingtonpost.com/wray-herbert/a-new-look-at-perception_b_2867621.html http://www.huffingtonpost.com/wray-herbert/a-new-look-at-per...): art historians used to think that El Greco's elongated figures were a result of his having a severe form of astigmatism. But, of course, if that had been the reason, he would have also seen an elongated canvass when painting, with the net result of figures painted in standard proportions. Here as well, if the tree painting was somewhow a reflection of Antico's tetrachromatism, she would have chosen colors that matched those that she sees on the eucalyptus. Such colors would be indistinguishable to us trichromats from the colors the tree does have, with the net result of a normally colored tree painting. At best, Antico is using something of a metaphor to convey her tetrachromatism. But no real insight on her vision.
- jrapdx3 12y ago
  I'm a printmaker (among other things), mostly making monotypes in recent years. The technique allows subtle color transitions which I deeply enjoy, and I notice particular pleasure of the visual effects of colors that range from green, yellow-green through orange and red. I've discovered that many art colleagues "don't get it", i.e., who seem not to discern the same subtleties that I appreciate. I'm beginning to think this may be due to differences in color discrimination. IOW whatever the basis for the difference I'm sure it would be measurable within limits of color vision test resolution. I don't know about the illustration in the article. Reproduction (especially reduced resolution) may very well coarsen the color so that the distinctions are run together, so no difference to see. You might want to try the on-line Farnswell-Munsell 100 test alluded to above which might be more informative.
  - Schiphol 12y ago
    As far as I can see, you are helping my point (perhaps that is what you intended): suppose that you saw those subtle transitions in, say, the wood of a kitchen table, and decided to make a printing that portrayed them. Suppose, as well, that your art colleagues have less color discrimination than you, and didn't see those transitions in wood color. They would also fails to see them in your printed portrait of them. So, you would have two entities, wood and print, which would match each other in color both for you and your colleagues. It's just that the colors thus matched would be beautiful and subtle for you, boring for them.
jrapdx3 12y ago
It's hard to compress what's known about the subject of color perception differences among people with nominally normal color vision. Hypothetical tetrachromacy has been demonstrated, that is, M and L cones with minor differences in peak spectral response existing in a retinal mosaic. The question arises whether this difference is capable of being propagated through the bipolar connecting neuronal paths (which form the "blue-yellow" and "red-green" channel paths conveying color info to the brain visual cortex). Several studies found no evidence for a "fourth channel", and some perceptual studies did not show confirmation of tetrachromacy. However a couple of studies do hint at rare female subjects who do seem to have good evidence for this trait. It is postulated that because of the differences in the exact genetic encodings on the 2 X chromosomes in females, that up to 50% of women have a retinal mosaic of 4 populations of cones, S M M' L, S M L L', and so on. The theory is that this allowed greater distinction of yellow to red color distinction which may have helped survival by avoiding toxic plants based on subtle color distinctions. In art, there are great colorists and those who are virtually incapable of subtle use of color. If anyone interested in finding out about their own abilities, check out: http://www.xrite.com/online-color-test-challenge http://www.xrite.com/online-color-test-challenge The on-line test is only a rough estimate, but it's fun and challenging. I suspect there's a spectrum, aka normal distribution of color discrimination ability. I should't say how well I did, though the results of trying it several times were remarkably consistent despite different computer systems that I used. BTW I encountered one very intriguing article reporting on a large sample of retinas obtained post-mortem. As expected, ~50% of females showed retinal mosaic of 2 M or L cones where only one each was expected. Most fascinating was the fact that of male retinas 8% showed a similar tetrachromat pattern. How that could arise is a mystery considering males have only one X chromosome. (There are pigment gene variations with greater number of CNV and TR which could be activated? But it's still a mystery.)
- jacobolus 12y ago
  > Hypothetical tetrachromacy has been demonstrated, that is, M and L cones with minor differences in peak spectral response existing in a retinal mosaic. The question arises whether this difference is capable of being propagated through the bipolar connecting neuronal paths (which form the "blue-yellow" and "red-green" channel paths conveying color info to the brain visual cortex). Adding genes for extra cone types into normally dichromatic mammals (mice or something? I don’t remember off hand and I don’t have the citation at my fingertips) has seemed in studies to result in trichromatic vision, so it’s not too big a leap to suspect that tetrachromacy of the type described in the article might happen for some humans. As you say there hasn’t been any study which showed this conclusively (that I’ve seen anyhow). I’d love to see more thorough research on these subjects who supposedly possess such vision. > In art, there are great colorists and those who are virtually incapable of subtle use of color. If anyone interested in finding out about their own abilities, check out: http://www.xrite.com/online-color-test-challenge http://www.xrite.com/online-color-test-challenge Note, this online test is a bit easier than the paper version of the Farnsworth–Munsell hue test, since the colors in the screen version end up with some lightness differences that make it a bit easier to keep some sections of the chart in order. Either way, the test IMO mostly measures (a) whether someone has “normal” trichromatic vision, and (b) how patient and willing to fiddle with fine details they are. I don’t personally think Farnsworth–Munsell test scores are super meaningful, though a very poor score does indicate some color vision deficiency. [FWIW, if I take the time to do the test slowly, either on screen or on paper, I consistently score ~0, occasionally mixing up one pair or another.] But anyway, I think the ability to be a good colorist in art has a whole lot to do with practice. Spending a lot of time mixing paint or color correcting photographs is likely to heighten awareness of tiny distinctions. For instance, I know that after a couple years of photography courses, several of my friends got much better at noticing color casts in photographs. Not that they couldn’t physically see them before, but after experience they more often spontaneously noticed the casts and started to have a feel for just how much adjustment in which direction would be necessary to counteract them.
bitL 12y ago
From my photography experience I noticed a lot more abnormalities than just tetrachromacy, which is not uncommon amongst artists. I had a model that was "seeing" colors in the sounds (synaesthesia) - she was often saying you talk to me in blue or that person has such a nice white voice. I've been tested for color vision and I am 100% accurate meaning I can discern subtle shades from each other precisely with no effort. I also have a very light form of synaesthesia manifesting itself by seeing a flash of light in the night right before an unexpected sudden loud noise (yet with observable latency) - like seeing a lightning just before hearing a thunder, even if the noise is not accompanied by any light. I was also always wondering if what I perceive as "blue" is the same as other people perceive as "blue"? What if the neural response in my brain wires the color sensation in the same way as other people perceive "green"? That would help to understand individual preferences for colors. Also, we know there are special cells in retina doing direction detection, edge detection etc. - what if this had a profound impact on how we individually perceive world around us? Somebody can have a strong edge or directional detection present in their view all the time, logically assuming it's normal for the others as well that are lacking that ability. We are just too diverse, and people are rather quiet in order not to risk being considered abnormal and marginalized, a common problem for artists in general.
- im3w1l 12y ago
  >seeing a flash of light in the night right before an unexpected sudden loud noise Does this improve your reaction time to sudden noises? You should totally test it :)
  - bitL 12y ago
    It's only a few milliseconds before the noise, I would have to develop Bruce Lee-grade reflexes to do anything about it ;-)
- emsy 12y ago
  I see this flash at nighttime as well and always thought that it was my sleepy brain jolting awake.
tgb 12y ago
Invisible colors? Boring. How about imaginary colors? http://en.wikipedia.org/wiki/Imaginary_color http://en.wikipedia.org/wiki/Imaginary_color
- vixin 12y ago
  How about David Lindsay's Arcturians (Voyage to Arcturus) who were able to see two extra colors namely jale and ulfire. https://en.wikipedia.org/wiki/A_Voyage_to_Arcturus https://en.wikipedia.org/wiki/A_Voyage_to_Arcturus
  - andrey-p 12y ago
    ... and a lot more fun to be had over here: http://en.wikipedia.org/wiki/List_of_fictional_colors http://en.wikipedia.org/wiki/List_of_fictional_colors
  - fennecfoxen 12y ago
    Octarine or GTFO ;)
cjo 12y ago
Also of interest is that birds have little oil droplets, often colored, as part of their visual set up. There are five different known types of color-filtering oil droplets (a sixth that is transparent) but it doesn't appear every bird has all of them. I'm no bird sight expert but it's suggested here [0] that a particular bird may have 8 effective color receptors (5 cones, 3 cone-droplet pairs) for a huge number of colors humans can't see. Diagrams of the receptors themselves can be found at the wiki [1]. [0] - http://watchingtheworldwakeup.blogspot.com/2008/11/mountain-biking-moonlight-color-vision.html http://watchingtheworldwakeup.blogspot.com/2008/11/mountain-... [1] - http://en.wikipedia.org/wiki/Bird_vision#Light_perception http://en.wikipedia.org/wiki/Bird_vision#Light_perception
kazinator 12y ago
The thing is, the woman doesn't seem to perceive new colors that other people do not; the colors others don't see are being aliased to familiar colors like "pink", and "red". (When she says "do you see that pink", is it a pink that we could see elsewhere? Or some color that we have no concept of, but which she relates to pinkness.) I'd be curious if she still sees the same thing in a digital image of the scene, or does the RGB system destroy it.
tuzakey 12y ago
The radiolab episode about colors talks about tetrachromats and some other very interesting stuff, worth a listen: http://www.radiolab.org/story/211119-colors/ http://www.radiolab.org/story/211119-colors/
burtonator 12y ago
There was a good study published recently documenting the ability for patients with eye surgery who could see into the UV spectrum. The cornea blocks some UV light so if you have eye correction surgery your cornea is now modified/thinner and you can see slightly into the UV spectrum. Probably has some downsides too.. Cataracts are probably more probable seeing as people tend to get them more frequently at higher altitude. The Tibetan people apparently have a high rate of cataracts since there is higher UV light at the higher altitude.
- glabifrons 12y ago
  It wasn't the cornea, but an artificial lens that was responsible. [0] UV passed through the artificial lens, but not through our natural one. It was replaced because of cataracts. [0] http://science.slashdot.org/story/12/02/14/165202/followup-ultraviolet-vision-after-cataract-surgery http://science.slashdot.org/story/12/02/14/165202/followup-u...
jwatte 12y ago
The frequency sensitivity curve of rods is different from reach of the cone types, too. If some rods contribute to daylight vision, then everyone is tetrachromatic to some extent.
gaius 12y ago
For an excellent fantasy take on this, see Brent Weeks Lightbringer books.
moneypenny 12y ago
Amazing, but I'm now terrified that there's a tiny group of guys who can hear frequencies nobody else can, and we will really have "golden ears" hi-fi-audiophile buffs.
edcastro 12y ago
I can actually see infrared on the dark quite easily. But I think it should be due to some falloff of the light spectrum emitted by the LED.
pjbrunet 12y ago
It's learnable and takes a lot of practice mixing colors and you need the right teacher. I picked up this ability in art school and it absolutely makes a sunset more beautiful. But to keep seeing this way you have to practice regularly. Use it or lose it. If I'm not painting regularly, it's gone. Like if you play chess for hours and hours every day, eventually you start to experience everything in terms of chess moves. It's the same with color. Look at just about any flat surface long enough and you'll notice it has a hue, saturation and value. Just go into Photoshop and you'll see that boring white wall has variations in hue, saturation and value, it's no medical mystery in my opinion. This part is a tiny more green, that part is a tiny more blue. I'm not giving you an art lesson here but you get the idea. Artists know they can make things look farther away by painting them blue/gray, decrease saturation with distance, etc. The painter learns to exaggerate because she just has a 2D surface to work with. Anyway, through the process of painting our perception of color improves, even when we're not painting. K-12 the goal is just paint the sky blue and the grass green, color inside the lines and get your grade. But if you want to be a serious painter at some point, you may want to look at things fresh, more intently. When people see your paintings, don't expect them to care how long it took to mix the color. Only a few artists will notice and they're not the ones buying your work. So even for artists, seeing color is not terribly useful, because mixing color is very time-consuming. It's more a hindrance than anything because I can finish an ink wash in 1/100th the time and sell that for the same price as an oil painting of the same subject. If you have all the time in the world and don't need money, I say go for it, buy some expensive oil paint and send me an email, I'll tell you what to buy. Stretch the canvas yourself and go all out.

194 points by austinz 12y ago

It's not that they see a few colors that no one perceives, it's that for them color is a 4 dimensional space instead of a 3 dimensional one. So it's a whole new world of different colors.

Houshalter 12y ago
Even though our eyes detect color in 3 dimensional space, that doesn't seem to be how we perceive it. E.g. I can't tell you how much red, green, or blue is in a color, just that it's close to the cluster of colors I recognize as "purple" or "blue" or "orange" or whatever. See this chart for example: http://imgs.xkcd.com/blag/satfaces_map_1024.png http://imgs.xkcd.com/blag/satfaces_map_1024.png Interestingly there is some evidence that culture and language might affect our perception of color.
- jacobolus 12y ago
  You are incorrect about that, and Randall’s drawing is misleading you (it shows the gamut boundary of an RGB cube, rather than the full three-dimensional color space he asked about in his survey). For people with “normal” trichromatic color vision, the color we perceive when looking at a particular spot does indeed fall into a three dimensional “color space”. You’re right that without careful attention/training it’s hard to state colors in terms of coordinates in terms of cone cell responses directly or color opponent signals (blue–yellow, red–green, white–black). It’s easy to train someone to give reasonably accurate color coordinates in terms of lightness, hue, and chroma, however. If you want to understand human color vision in detail, I recommend this online resource: http://www.handprint.com/LS/CVS/color.html http://www.handprint.com/LS/CVS/color.html
- amitp 12y ago
  We seem to perceive it in something closer to hsl space (3d) than rgb space (also 3d). You can tell that it's "purple" but you can also tell whether it's saturated or not, and if it's bright or dark purple. Also check out Lab space: http://en.wikipedia.org/wiki/Lab_color_space http://en.wikipedia.org/wiki/Lab_color_space
- canjobear 12y ago
  > Interestingly there is some evidence that culture and language might affect our perception of color. The evidence for effects of language on color perception is very weak, or it indicates that the effects are themselves very weak. The big paper in this field is this: http://www.languagescience.umd.edu/~ellenlau/courses/ling440/Winawer_2007.pdf http://www.languagescience.umd.edu/~ellenlau/courses/ling440... They find that Russian speakers, who have separate words for two shades of blue, can discriminate between those shades of blue something like 50 ms faster than they can discriminate between two shades of blue that fall into the same color word category. First thing to note, that's a very small difference. Second thing: the effect goes away under verbal interference (like when you have the subjects repeat a word over and over again while doing the color discrimination task). So I guess there's an effect of language on color perception, but not while you're talking? It definitely doesn't seem to me that the colors I am perceiving change when I am talking vs. when I am not. Third, there's a huge overall reaction time difference between the Russian and English speakers in the paper, which calls into question how well the experiment was really run. So it's not clear that there really are effects of culture/language on color perception; and if they do exist they are very small. (At least that's the conclusion I would draw from this paper, which is widely cited in that field. I'd be interested to hear of different results if they're out there.)

shutupalready 12y ago

> Jordan’s “acid test” involved coloured discs showing different mixtures of pigment, such as a green made of yellow and blue. The mixtures were too subtle for most people to notice: almost all people would see the same shade of olive green, but each combination should give out a subtly different spectrum of light that would be perceptible to someone with a fourth cone. From what I understand, a modern monitor is capable of displaying the entire range of colors perceptible to the human eye. Am I mistaken about that? So would it not be possible to create a web-based version of these "coloured discs", and then we can test ourselves.

sigterm 12y ago
> Am I mistaken about that? Yes. See: https://en.wikipedia.org/wiki/Gamut https://en.wikipedia.org/wiki/Gamut
TheSpiceIsLife 12y ago
Google 'tetrachromacy test', first hit http://www.blogadilla.com/2008/06/08/are-you-a-tetrachromat/ http://www.blogadilla.com/2008/06/08/are-you-a-tetrachromat/
- sigterm 12y ago
  that claim is quite dubious. I don't think it's possible to create metamers for people with normal 3-color vision on an RGB monitor. To do that you need an extra degree of freedom. https://en.wikipedia.org/wiki/Metamerism_(color) https://en.wikipedia.org/wiki/Metamerism_(color)
  - Xcelerate 12y ago
    Hmm... I'm not sure about that. It's an interesting question. It's equivalent to the question: can we create two images on a computer monitor that appear the same to a person with normal color vision yet appear different to a colorblind person? I think it would depend on the particular mapping from 3 to 2 dimensions... it might be possible.

Kiro 12y ago

Am I the only one who thinks her painting of the tree looks the same as the photo color wise?

oska 12y ago

I'm from Australia but hadn't heard of the Rainbow Eucalypt before (the tree that the featured tetrachromat painted). That's not so unlikely as there are a lot of Eucalyptus species. Still, I was curious and so looked it up and was very interested to find that it is a Eucalypt from outside Australia and, more than that, the only one whose native region partly lies within the northern hemisphere. Another name for it is the Mindanao gum, as it is native to the tropical rainforests of Mindanao in the Philippines (north of the equator). http://en.wikipedia.org/wiki/Eucalyptus_deglupta http://en.wikipedia.org/wiki/Eucalyptus_deglupta

philh 12y ago

> The crux of Jordan’s argument lay in the fact that the gene for our red and green cone types lies on the X chromosome. Since women have two X chromosomes, they could potentially carry two different versions of the gene, each encoding for a cone that is sensitive to slightly different parts of the spectrum. In addition to the other two, unaffected cones, they would therefore have four in total – making them a “tetrachromat”. Why couln't this happen for either of the other cones?

jacobolus 12y ago
The gene for the “short” wavelength cone† is located on chromosome 7, whereas the genes for the others are located on the X chromosome. Since females have two X chromosomes, it is possible for them to have 2 variant copies of the long or medium cone genes. (Since males only have one X chromosome, color vision deficiencies caused by a missing or abnormal copy of one of the medium/long cone pigment genes are much more common than for females.) It would certainly be possible for a genetic mutation to result in an extra mutated copy of the short cone pigment gene, but I don’t think I’ve heard of variants of this gene with slightly different light sensitivity than the usual type (they might exist though?). By contrast “non-standard” version of the medium cone pigment gene is relatively common. See: http://ghr.nlm.nih.gov/gene/OPN1SW http://ghr.nlm.nih.gov/gene/OPN1SW http://ghr.nlm.nih.gov/gene/OPN1MW http://ghr.nlm.nih.gov/gene/OPN1MW http://ghr.nlm.nih.gov/gene/OPN1MW2 http://ghr.nlm.nih.gov/gene/OPN1MW2 http://ghr.nlm.nih.gov/gene/OPN1LW http://ghr.nlm.nih.gov/gene/OPN1LW † We should properly refer to the cones as long, medium, and short rather than red, green, and blue, since color is computed from differences in cone responses.
gus_massa 12y ago
The male equivalent is "Anomalous trichromacy" http://en.wikipedia.org/wiki/Color_blindness#Anomalous_trichromacy http://en.wikipedia.org/wiki/Color_blindness#Anomalous_trich.... You have one of the color receptors tuned to a slightly different frequency, so you see the word in a different way. (Which way is the correct way?) This condition is easy to spot with the standard Ishihara color test, so it's easy to measure the % of the population in these cases. --- Green The most common case of male anomalous trichromacy is the "wrong/unusual" green receptor case, so the most common case of woman tetracromat is one that has 2 copies of the usual blue receptor, 2 copies of the usual red receptor and 1 copy of the usual green receptor 1 copy of the unusual green receptor. This is the case discussed in the article. To reduce the text size I'll denote this kind of tetracromat with BBGgRR, where the capital letter denote the usual color receptor and the noncapital letter denote the unusual color receptor. (This is unrelated to recessive and dominant genes that are usually denoted by capital and noncapital letters.) --- Red The second most common case of male anomalous trichromacy is the "wrong/unusual" red receptor case, so the seccond most common case of woman tetracromat is BBGGRr (1 copy of the usual red receptor an 1 copy of the unusual red receptor). Obviously, you can have both mixed copies, so a woman can have BBGgRr and be a pentacromat. At least have the genes to "see" in a 5-dimensional color space. If she can use this ability is less clear. --- Blue The least common case of male anomalous trichromacy is the "wrong/unusual" blue receptor case, so the least common case of woman tetracromat is BbGGRR. It can be mixed with the other cases, so a woman can be pentacromat or hexacromat. The interesting part is that the blue gene is not in the X chromosome, so both male and females have two copies. So a male can be tetracromat BbG_R_ . But this chromosome is not inactivated as the 50% of the X chromosomes in females. So I'm not sure if it's possible to have a different kind of vision in this case. --- It's more complicated Actually you can have more than 1 copy of the color genes in each chromosome, and there are more than two variations of each gene, so it's more complicated.

jimmytidey 12y ago

Mantis Shrimps have 12 photoreceptors, they can also see in all polarisations. They don't do paintings so it's hard to know how they experience this. http://en.wikipedia.org/wiki/Mantis_shrimp#Eyes http://en.wikipedia.org/wiki/Mantis_shrimp#Eyes

Schiphol 12y ago

Antico's painting of an eucalyptus doesn't "give us a hint of the extra shades she is seeing". It's just another instance of the [El Greco fallacy](http://www.huffingtonpost.com/wray-herbert/a-new-look-at-perception_b_2867621.html http://www.huffingtonpost.com/wray-herbert/a-new-look-at-per...): art historians used to think that El Greco's elongated figures were a result of his having a severe form of astigmatism. But, of course, if that had been the reason, he would have also seen an elongated canvass when painting, with the net result of figures painted in standard proportions. Here as well, if the tree painting was somewhow a reflection of Antico's tetrachromatism, she would have chosen colors that matched those that she sees on the eucalyptus. Such colors would be indistinguishable to us trichromats from the colors the tree does have, with the net result of a normally colored tree painting. At best, Antico is using something of a metaphor to convey her tetrachromatism. But no real insight on her vision.

jrapdx3 12y ago
I'm a printmaker (among other things), mostly making monotypes in recent years. The technique allows subtle color transitions which I deeply enjoy, and I notice particular pleasure of the visual effects of colors that range from green, yellow-green through orange and red. I've discovered that many art colleagues "don't get it", i.e., who seem not to discern the same subtleties that I appreciate. I'm beginning to think this may be due to differences in color discrimination. IOW whatever the basis for the difference I'm sure it would be measurable within limits of color vision test resolution. I don't know about the illustration in the article. Reproduction (especially reduced resolution) may very well coarsen the color so that the distinctions are run together, so no difference to see. You might want to try the on-line Farnswell-Munsell 100 test alluded to above which might be more informative.
- Schiphol 12y ago
  As far as I can see, you are helping my point (perhaps that is what you intended): suppose that you saw those subtle transitions in, say, the wood of a kitchen table, and decided to make a printing that portrayed them. Suppose, as well, that your art colleagues have less color discrimination than you, and didn't see those transitions in wood color. They would also fails to see them in your printed portrait of them. So, you would have two entities, wood and print, which would match each other in color both for you and your colleagues. It's just that the colors thus matched would be beautiful and subtle for you, boring for them.

jrapdx3 12y ago

It's hard to compress what's known about the subject of color perception differences among people with nominally normal color vision. Hypothetical tetrachromacy has been demonstrated, that is, M and L cones with minor differences in peak spectral response existing in a retinal mosaic. The question arises whether this difference is capable of being propagated through the bipolar connecting neuronal paths (which form the "blue-yellow" and "red-green" channel paths conveying color info to the brain visual cortex). Several studies found no evidence for a "fourth channel", and some perceptual studies did not show confirmation of tetrachromacy. However a couple of studies do hint at rare female subjects who do seem to have good evidence for this trait. It is postulated that because of the differences in the exact genetic encodings on the 2 X chromosomes in females, that up to 50% of women have a retinal mosaic of 4 populations of cones, S M M' L, S M L L', and so on. The theory is that this allowed greater distinction of yellow to red color distinction which may have helped survival by avoiding toxic plants based on subtle color distinctions. In art, there are great colorists and those who are virtually incapable of subtle use of color. If anyone interested in finding out about their own abilities, check out: http://www.xrite.com/online-color-test-challenge http://www.xrite.com/online-color-test-challenge The on-line test is only a rough estimate, but it's fun and challenging. I suspect there's a spectrum, aka normal distribution of color discrimination ability. I should't say how well I did, though the results of trying it several times were remarkably consistent despite different computer systems that I used. BTW I encountered one very intriguing article reporting on a large sample of retinas obtained post-mortem. As expected, ~50% of females showed retinal mosaic of 2 M or L cones where only one each was expected. Most fascinating was the fact that of male retinas 8% showed a similar tetrachromat pattern. How that could arise is a mystery considering males have only one X chromosome. (There are pigment gene variations with greater number of CNV and TR which could be activated? But it's still a mystery.)

jacobolus 12y ago
> Hypothetical tetrachromacy has been demonstrated, that is, M and L cones with minor differences in peak spectral response existing in a retinal mosaic. The question arises whether this difference is capable of being propagated through the bipolar connecting neuronal paths (which form the "blue-yellow" and "red-green" channel paths conveying color info to the brain visual cortex). Adding genes for extra cone types into normally dichromatic mammals (mice or something? I don’t remember off hand and I don’t have the citation at my fingertips) has seemed in studies to result in trichromatic vision, so it’s not too big a leap to suspect that tetrachromacy of the type described in the article might happen for some humans. As you say there hasn’t been any study which showed this conclusively (that I’ve seen anyhow). I’d love to see more thorough research on these subjects who supposedly possess such vision. > In art, there are great colorists and those who are virtually incapable of subtle use of color. If anyone interested in finding out about their own abilities, check out: http://www.xrite.com/online-color-test-challenge http://www.xrite.com/online-color-test-challenge Note, this online test is a bit easier than the paper version of the Farnsworth–Munsell hue test, since the colors in the screen version end up with some lightness differences that make it a bit easier to keep some sections of the chart in order. Either way, the test IMO mostly measures (a) whether someone has “normal” trichromatic vision, and (b) how patient and willing to fiddle with fine details they are. I don’t personally think Farnsworth–Munsell test scores are super meaningful, though a very poor score does indicate some color vision deficiency. [FWIW, if I take the time to do the test slowly, either on screen or on paper, I consistently score ~0, occasionally mixing up one pair or another.] But anyway, I think the ability to be a good colorist in art has a whole lot to do with practice. Spending a lot of time mixing paint or color correcting photographs is likely to heighten awareness of tiny distinctions. For instance, I know that after a couple years of photography courses, several of my friends got much better at noticing color casts in photographs. Not that they couldn’t physically see them before, but after experience they more often spontaneously noticed the casts and started to have a feel for just how much adjustment in which direction would be necessary to counteract them.

bitL 12y ago

From my photography experience I noticed a lot more abnormalities than just tetrachromacy, which is not uncommon amongst artists. I had a model that was "seeing" colors in the sounds (synaesthesia) - she was often saying you talk to me in blue or that person has such a nice white voice. I've been tested for color vision and I am 100% accurate meaning I can discern subtle shades from each other precisely with no effort. I also have a very light form of synaesthesia manifesting itself by seeing a flash of light in the night right before an unexpected sudden loud noise (yet with observable latency) - like seeing a lightning just before hearing a thunder, even if the noise is not accompanied by any light. I was also always wondering if what I perceive as "blue" is the same as other people perceive as "blue"? What if the neural response in my brain wires the color sensation in the same way as other people perceive "green"? That would help to understand individual preferences for colors. Also, we know there are special cells in retina doing direction detection, edge detection etc. - what if this had a profound impact on how we individually perceive world around us? Somebody can have a strong edge or directional detection present in their view all the time, logically assuming it's normal for the others as well that are lacking that ability. We are just too diverse, and people are rather quiet in order not to risk being considered abnormal and marginalized, a common problem for artists in general.

im3w1l 12y ago
>seeing a flash of light in the night right before an unexpected sudden loud noise Does this improve your reaction time to sudden noises? You should totally test it :)
- bitL 12y ago
  It's only a few milliseconds before the noise, I would have to develop Bruce Lee-grade reflexes to do anything about it ;-)
emsy 12y ago
I see this flash at nighttime as well and always thought that it was my sleepy brain jolting awake.

tgb 12y ago

Invisible colors? Boring. How about imaginary colors? http://en.wikipedia.org/wiki/Imaginary_color http://en.wikipedia.org/wiki/Imaginary_color

vixin 12y ago
How about David Lindsay's Arcturians (Voyage to Arcturus) who were able to see two extra colors namely jale and ulfire. https://en.wikipedia.org/wiki/A_Voyage_to_Arcturus https://en.wikipedia.org/wiki/A_Voyage_to_Arcturus
- andrey-p 12y ago
  ... and a lot more fun to be had over here: http://en.wikipedia.org/wiki/List_of_fictional_colors http://en.wikipedia.org/wiki/List_of_fictional_colors
- fennecfoxen 12y ago
  Octarine or GTFO ;)

cjo 12y ago

Also of interest is that birds have little oil droplets, often colored, as part of their visual set up. There are five different known types of color-filtering oil droplets (a sixth that is transparent) but it doesn't appear every bird has all of them. I'm no bird sight expert but it's suggested here [0] that a particular bird may have 8 effective color receptors (5 cones, 3 cone-droplet pairs) for a huge number of colors humans can't see. Diagrams of the receptors themselves can be found at the wiki [1]. [0] - http://watchingtheworldwakeup.blogspot.com/2008/11/mountain-biking-moonlight-color-vision.html http://watchingtheworldwakeup.blogspot.com/2008/11/mountain-... [1] - http://en.wikipedia.org/wiki/Bird_vision#Light_perception http://en.wikipedia.org/wiki/Bird_vision#Light_perception

kazinator 12y ago

The thing is, the woman doesn't seem to perceive new colors that other people do not; the colors others don't see are being aliased to familiar colors like "pink", and "red". (When she says "do you see that pink", is it a pink that we could see elsewhere? Or some color that we have no concept of, but which she relates to pinkness.) I'd be curious if she still sees the same thing in a digital image of the scene, or does the RGB system destroy it.

tuzakey 12y ago

The radiolab episode about colors talks about tetrachromats and some other very interesting stuff, worth a listen: http://www.radiolab.org/story/211119-colors/ http://www.radiolab.org/story/211119-colors/

burtonator 12y ago

There was a good study published recently documenting the ability for patients with eye surgery who could see into the UV spectrum. The cornea blocks some UV light so if you have eye correction surgery your cornea is now modified/thinner and you can see slightly into the UV spectrum. Probably has some downsides too.. Cataracts are probably more probable seeing as people tend to get them more frequently at higher altitude. The Tibetan people apparently have a high rate of cataracts since there is higher UV light at the higher altitude.

glabifrons 12y ago
It wasn't the cornea, but an artificial lens that was responsible. [0] UV passed through the artificial lens, but not through our natural one. It was replaced because of cataracts. [0] http://science.slashdot.org/story/12/02/14/165202/followup-ultraviolet-vision-after-cataract-surgery http://science.slashdot.org/story/12/02/14/165202/followup-u...

jwatte 12y ago

The frequency sensitivity curve of rods is different from reach of the cone types, too. If some rods contribute to daylight vision, then everyone is tetrachromatic to some extent.

gaius 12y ago

For an excellent fantasy take on this, see Brent Weeks Lightbringer books.

moneypenny 12y ago

Amazing, but I'm now terrified that there's a tiny group of guys who can hear frequencies nobody else can, and we will really have "golden ears" hi-fi-audiophile buffs.

edcastro 12y ago

I can actually see infrared on the dark quite easily. But I think it should be due to some falloff of the light spectrum emitted by the LED.

pjbrunet 12y ago

It's learnable and takes a lot of practice mixing colors and you need the right teacher. I picked up this ability in art school and it absolutely makes a sunset more beautiful. But to keep seeing this way you have to practice regularly. Use it or lose it. If I'm not painting regularly, it's gone. Like if you play chess for hours and hours every day, eventually you start to experience everything in terms of chess moves. It's the same with color. Look at just about any flat surface long enough and you'll notice it has a hue, saturation and value. Just go into Photoshop and you'll see that boring white wall has variations in hue, saturation and value, it's no medical mystery in my opinion. This part is a tiny more green, that part is a tiny more blue. I'm not giving you an art lesson here but you get the idea. Artists know they can make things look farther away by painting them blue/gray, decrease saturation with distance, etc. The painter learns to exaggerate because she just has a 2D surface to work with. Anyway, through the process of painting our perception of color improves, even when we're not painting. K-12 the goal is just paint the sky blue and the grass green, color inside the lines and get your grade. But if you want to be a serious painter at some point, you may want to look at things fresh, more intently. When people see your paintings, don't expect them to care how long it took to mix the color. Only a few artists will notice and they're not the ones buying your work. So even for artists, seeing color is not terribly useful, because mixing color is very time-consuming. It's more a hindrance than anything because I can finish an ink wash in 1/100th the time and sell that for the same price as an oil painting of the same subject. If you have all the time in the world and don't need money, I say go for it, buy some expensive oil paint and send me an email, I'll tell you what to buy. Stretch the canvas yourself and go all out.