# Talk:Tetrachromacy

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Why is there a student essay referring to a study on female human tetrachromates as an external link instead of the study itself - or at least a more normal article reporting on the study like http://scienceblogs.com/cognitivedaily/2005/09/do_women_perceive_color_differ.php --Troed 21:45, 23 January 2007 (UTC)

Mat-C I am working on a longer version of this which will be appearing shortly.

Does anyone know if the restriction "vertebrate" is true or not? This seems either unusually wide (Trichromat seems to refer to humans only) or unusually narrow (to exclude a wide range of animals). --Mat 18:04, 6 Mar 2004 (UTC)

www.dictionary.com states "tetrachromat" as being human with 4 colour vision. Some sources claim most humans are tetrachromatic due to the presence of rods and the possibility this contributes slightly to colour vision. --/Mat 21:34, 6 Mar 2004 (UTC)

Hi Mat-C.

Anything with vision can be described as a monochromat, dichromat, tetrachromat, etc. Ken McE 02:47, 14 August 2007 (UTC)

The word could also be used for man-made systems, as well as animals. I can imagine police using traffic cameras that distinguish among colours of vehicles that the eye sees as identical! --195.137.93.171 23:14, 7 September 2007 (UTC)

## Tetrachromats can only be female!

The article states that over 50% of women and 8% of men may be tetrachromats. The linked reference has no mention of male tetrachromats, and other references make it clear that tetrachromats can only occur in females (or at least people with two X chromosomes) I think the statement is a misquote? 59.167.121.128 (talk) 14:51, 28 August 2008 (UTC)

However, there are some men born with two or more extra X chromosomes. (eg. XXY, XXXY etc.) There are also sometimes children born that are the product of two eggs fused together. (Chimeras) Therefore it should be possible in extremely rare situations for men to be tetrachromats. — Preceding unsigned comment added by 64.180.198.201 (talk) 08:06, 3 November 2012 (UTC)

Also, I (not the previous commenter) recommend this change:

"The biological basis for this phenomenon is X-inactivation."

TO:

"The biological basis for this phenomenon is X-inactivation. Each cell randomly switches off all but one X chromosome. In normal females, if each X chromosome has different alleles of a cone pigment gene, each having different sensitivities over the electromagnetic spectrum, half of the cells in the retina would be one variant, and half would be the other." 128.113.74.14 (talk) 22:56, 18 August 2009 (UTC)

You all forogt something. This is just a theory! It is possible that there are some men with tetrachromacy, we just do not know, and current understanding is that there should be no men with tetrachromacy. But who knows? Dr. Neitz said it can only be a female, but he also can be wrong. --91.213.255.7 (talk) 20:09, 13 November 2010 (UTC)

All humans are tetrachromats, but the eye lens blocks the light the 4th cone responds to. Instead, some women are pentachromats. rdococ... (talk) 08:14, 26 May 2012 (UTC)

The human lens blocks UV, but it is supposed to do that. What fourth cone are you referring to? Ken McE (talk) 19:33, 9 December 2012 (UTC)

While I do agree that it is not possible for males to be born naturally tetrachromats, it's possible that a transsexual man who was born as tetrachromat girl can qualify as a legitimate tetrachromat male. He still has those four cones. — Preceding unsigned comment added by Nosferatuslayer (talkcontribs) 00:40, 29 September 2013 (UTC)

An article about vision is perhaps not the best place to start a discussion about what we do or do not count as female. In relation to this article, "male" is a person with one or more "Y" chromosomes and "female" is any person with only "X" chromosomes.

Ken McE (talk) 01:38, 5 June 2017 (UTC)

It is actually possible for males to be tetrachromats if they recieved transplanted eyes from a female donor who was a tetrachromat. — Preceding unsigned comment added by 99.235.74.54 (talk) 21:21, 26 January 2014 (UTC)

Just getting a new sensor is not good enough. You need to somehow run a new signal through the old optic nerve, and you need the brain to be able to make sense of the new data. These are non-trivial problems.

Ken McE (talk) 01:38, 5 June 2017 (UTC)

## Mammalian species

"It has not yet been demonstrated as a characteristic property of any mammalian species, though it is likely that it occurs in some birds, fish, amphibians, reptiles and insects."

As far as I recall, insects aren't mammals. 82.139.47.117 00:02, 6 June 2006 (UTC)

Exactly, and this is precisely what the author of the quoted sentence said. It seems you misread the sentence and thought the author included insects as a kind of mammal although that isn't what was actually written. Interlingua talk email 00:20, 11 July 2006 (UTC)
What about marsupials? The main color article claims that "most marsupials" are tetrachromats. One of these articles is very wrong.
Reindeer can see ultraviolet. For more info, see the Wikipedia's article reindeer or Google reindeer and ultraviolet. Zyxwv99 (talk) 02:27, 3 September 2013 (UTC)

## uhm

In Calomhe's article, "Up to 50 per cent of women are tetrachromatic and can use their extra pigments in 'contextually rich viewing circumstances'.", she must've meant "Up to 50 per cent of women who are tetrachromatic can use their extra pigments in 'contextually-rich viewing circumstances'."

We desperately need a test for tetrachromacy, and for tetrachromats to point out where extra divisions of hues are, say, on the RGB wheel. Do tetrachromats see a breakup of symmetry on the wheel? Also, whenever I see red I get an odd feeling that the red is always tinged with orange. Is this true of most people, or is this a tetrachromatic effect, or am I just slightly red-blind? I do though, in principle, understand and see the difference between red and orangey-red. lysdexia 03:03, 23 Nov 2004 (UTC)

personally I dont believe any 4 cone cell humanoids exist, but if they do and the brain is able to make use of it, its another color dimension: (leaving out intensity) instead of a 2 dimensional color plane it would be a 3 dimensional color space. it doesnt fit in new colors within the 2d color wheel. — Preceding unsigned comment added by 157.193.9.140 (talk) 11:33, 28 July 2011 (UTC)

also, leaving out a color would have a similar effect as any colorspace projection of an image such as grayscale image, red or green or blue filtered image or any superposition of these. I think you would notice if you can see real life objects in color but everything on computer displays seem blue or gray or ... this would be a rather known phenomenon. This should be very easy to verify with correctly designed AB-X tests. — Preceding unsigned comment added by 157.193.9.140 (talk) 11:38, 28 July 2011 (UTC)

A few weeks ago I read an article in an ophthalmology journal about this, only I forgot to take notes. They tested twenty thousand women with the gene for tetrachromacy and found that it was only expressed in one person. She had a fourth cone somewhere within the normal range of vision, in between two of the other cones (in terms of peak sensitivity). They subjected her to a battery of vision and color perception tests. As far as they could tell, the fourth cone had absolutely no effect. Zyxwv99 (talk) 02:33, 3 September 2013 (UTC)

According to Dawkins's "The Ancestor's Tale", not only are most non-mammalian vertebrates at least trichromatic, but many are tetrachromatic or (in the case of some birds and turtles) even pentachromatic. Mammals, considered as a whole, have pretty miserable color vision probably due to our nocturnal roots. Interestingly, certain marsupials apparently kept a reptilian retina pigment that all other mammals have lost. Old-world primates, and howler monkeys have re-created trichromatic vision rather than simply "reverting" to it. Human trichromatic vision is based on the blue cone, and two green cones. One of the green cones, however, has shifted its reception range to something closer to yellow, with a sharp drop-off in responsiveness as it moves toward green; we call it our red receptor. The similarity of our red and green receptors are the primary reason they are miscopied during gene cross-over. This, in combination with the green cone genes' location on the X chromosome, results in a relatively high number of color-blind individuals. Females are rarely color-blind because even if one X chromosome has a faulty gene, the other is likely to be intact. Males, of course, only get one X chromosome.

All of this background is important in understanding tetrachromacy in humans. It is restricted to females because only females will have a chance to have two "different" green cone genes expressed in a single individual. The cause is likely to be the presence on one X chromosome of two green cone genes. The other X chromosome has a red and green cone gene as usual. If all are expressed, then the individual will have red cones, green cones, a second set of green cones, and blue cones. It is likely that the green cones' peak response wavelength will vary at least slightly. This results in improved color resolution in the individual. Bear in mind it is possible for the red cone gene to undergo the same process, as it apparently has in the individual mentioned in this article.

Unfortunately there is a good chance that sons of human tetrachromats will be color blind, as they may inherit the X chromosome that bears 2 green cone genes; without the extra X chromosome, they will be red-green color-blind.

A lot of this info comes from Richard Dawkins's "The Ancestor's Tale", pp 145-155. --Verteiron 03:54:55, 2005-09-13 (UTC)

## Human Tetrachromats??

I am concerned about they way this article suggests that there are human tetrachromats walking among us. In theory it may be possible, in practice I am not aware of any fully confirmed cases.Ken McE (talk) 23:36, 21 December 2007 (UTC)

I find the current formulation ("It has been suggested that women who are carriers for variant cone pigments may be born as full tetrachromats") overly cautious. I am not advocating that the we present the theory of female human tetrachromats as a fact, but this formulation almost ridicules the possibility that the theory may be true. — Adhemar 20:35, 14 September 2006 (UTC)

I agree that it is cautious but feel that some caution is appropriate. In science, extraordinary claims require extraordinary evidence.Ken McE (talk) 23:36, 21 December 2007 (UTC)

According to an article I read, the possibility of human tetrachromats is actually quite optimistic -- claimed that up to %50 of females may be tetrachromats. --steve —Preceding unsigned comment added by 128.100.71.45 (talk) 19:23, 25 May 2010 (UTC)

Citation? Ken McE (talk) 02:46, 4 July 2010 (UTC)

http://www.klab.caltech.edu/cns186/papers/Jameson01.pdf suggests that as many as 50% of heterochromatic women express tetrachromacy. This is not the same thing as saying "50% of women". It's likely more like 2-3% of women. Also, caution when using the source I just cited. It's a well-designed double blind study with not enough analysis and a small trial size. More research definitely needs to be done. ◗●◖ falkreon (talk) 10:14, 10 January 2011 (UTC)

## Wartime Experiments

http://vm.uconn.edu/~lundquis/links.html suggests diet can extend IR senstivity but http://www.google.co.uk/search?q=carrots+night+vision suggests this may be propaganda. Doubt if it's a 4th channel, though !

--195.137.93.171 00:41, 8 September 2007 (UTC)

## Is it true?

Can Tetrachromacy allow animals to see colors that is unimaginable?—The preceding unsigned comment was added by Ko34 (talkcontribs) 13:43, 12 November 2006 (UTC).

Tetrachromacy would allow an animal to see colours that are not imaginable (or more accurately distinguishable) by Trichromatids. This is exactly the same effect seen with colour-blind people - someone with red/green colour-blindness is unable to see the difference, so cannot 'imagine' red and green because they look the same. Rob.desbois 15:03, 20 November 2006 (UTC)

I think "not imaginable" is an accurate description. Consider that monochromat vision is seeing the world like in a B&W movie, and those whose visual experience has been always like that cannot even imagine what the colors other than white, black and grey "look like"—they lack the psychological experience of color qualia like red, yellow, green or blue, because their visual system has never prompted those chromatic sensations in their minds, just like born-blind people cannot even imagine what it is like to see because they have never experienced in their minds the sensation of perceiving light. Dichromats cannot "distinguish red from green", but not because of some strange cognitive impairment that makes them somehow "confuse" two such distinct color percepts, but because the lights that a trichromat experiences as reddish or greenish they instead experience as yellowish, whitish or bluish (that's the way John Dalton described how the rainbow looked to him); so it's not really that they "confuse" red and green the way a trichromat might mistakenly understand that statement (confusion of the red and green percepts), it's that to them red and green are unthinkable color percepts lying outside the range of their subjective chromatic experience, and two lights that a trichromat perceives distinctly as red and green might be metamers to a dichromat, looking to them nothing like red or green but as some same yellowish shade, thus appearing to trichromats as though they are "confusing" red and green (but it's no different from us trichromats "confusing" a pure spectral yellow light from a composite #xFFFF00 RGB light, which physically are very distinct spectrums, i.e. different "physical colors", but that to us look the same perceptual color, so we don't think of it in terms of "confusing" colors, but instead in terms of those lights being merely "metamers" of the "same color" yellow). Trichromats lack the subjective experience of the qualia corresponding to the "fourth" color dimension, which most birds can enjoy but that we humans have never experienced, so for us the colors from that fourth chromatic dimension are literally unthinkable, lying outside the range of our chromatic experience. Although we may hypothesize how a tetrachromatic color space could be organized at the perceptual level:
1. A monochromat perceives a single achromatic dimension: black-to-white, resulting in a 1D perceptual color space, with two elementary color percepts (white, black) that combined result in three achromatic perceptual color categories:
Achromatic colors:
• pure achromatic (1 component percept): white (white), black (black)
• mixed achromatic (2 component percepts): white+black (grey)
2. A dichromat adds an opponent chromatic dimension: yellow-vs-blue, resulting in a 2D perceptual color space, with four elementary color percepts (white, black, yellow, blue) that combined form a range of "new" perceptual color categories unknown (literally unimaginable) to monochromats, including the perception of color hues, which to a monochromat is a novel concept (they only know about achromatic colors):
Achromatic colors:
• pure achromatic (1 component percept): white (white), black (black)
• mixed achromatic (2 component percepts): white+black (grey)
Chromatic saturated colors:
• unary chromatic (1 component percept): yellow (yellow), blue (blue)
Chromatic insaturated colors:
• unary chromatic + pure achromatic (2 component percepts): yellow+white (beige), yellow+black (dark yellow, ochre), blue+white (azure), blue+black (navy),
• unary chromatic + mixed achromatic (3 component percepts): yellow+white+black (yellowish grey), blue+white+black (bluegrey)
3. A trichromat adds another opponent chromatic dimension: red-vs-green, resulting in a 3D perceptual color space, with six elementary color percepts (white, black, yellow, blue, red, green) that combined form a wide range of "new" perceptual color categories unknown to dichromats, including the perception of binary hues (such as orange and purple), which to a dichromat is a novel concept (they only know about unary hues):
Achromatic colors:
• pure achromatic (1 component percept): white (white), black (black)
• mixed achromatic (2 component percepts): white+black (grey)
Chromatic saturated colors:
• unary chromatic (1 component percept): red (red), yellow (yellow), green (green), blue (blue)
• binary chromatic (2 component percepts): red+yellow (orange), yellow+green (yellowgreen, chartreuse), green+blue (bluegreen, turquoise), blue+red (purple)
Chromatic insaturated colors:
• unary chromatic + pure achromatic (2 component percepts): red+white (pink), red+black (maroon), yellow+white (beige), yellow+black (dark yellow, ochre), green+white (mint green), green+black (forest green), blue+white (azure), blue+black (navy)
• binary chromatic + pure achromatic (3 component percepts): red+yellow+white (peach, salmon), red+yellow+black (brown), yellow+green+white (light yellowgreen), yellow+green+black (dark yellowgreen, olive green), green+blue+white (light turquoise) , green+blue+black (dark turquoise, teal), blue+red+white (light purple, lilac), blue+red+black (dark purple)
• unary chromatic + mixed achromatic (3 component percepts): red+white+black (reddish grey), yellow+white+black (yellowish grey), green+white+black (greenish grey), blue+white+black (bluegrey)
• binary chromatic + mixed achromatic (4 component percepts): red+yellow+white+black (greybrown, taupe), yellow+green+white+black (olive brown, khaki), green+blue+white+black (greyish turquoise) , blue+red+white+black (brownish purple, puce)
4. A tetrachromat, by analogy, might add another opponent chromatic dimension, which is unnamed in human languages because it is unknown to trichromat humans—but for the sake of argument let's name this fourth dimension septarine-vs-octarine (from the "color of magic" and the fact that septarine and octarine would be the 7th and 8th elementary color percepts after white, black, yellow, blue, red and green). The resulting perceptual color space would be 4D, and would comprise all color categories (with all their shades) that can be obtained by combining up to 5 non-mutually-opponent elementary percepts (white and/or black and/or (yellow or blue) and/or (red or green) and/or (septarine or octarine)), giving rise to a plethora of color categories unknown to trichromats, including the perception of ternary hues, which to a trichromat is a novel concept (saturated colors that are the simultaneous experience of three elementary hues, such as red+yellow+octarine "octarinish orange", while trichromats can only experience unary or binary hues and dichromats only unary hues).
Uaxuctum 16:35, 9 January 2007 (UTC)
tl;dr -134.84.102.237 (talk) 12:27, 18 April 2008 (UTC)

they aren't capable of seeing "unimaginable colours" THAT DOESN'T EVEN MAKE ANY SENSE. Rather, they would be capable of discerning a greater variety of colour, for example. Colour blind people are just incapable of telling some dissimilar colours apart; similarily, a tetrachromat would have higher resolving power that would enable them to distinguish between two colours that would appear identical to a trichromat. -steve —Preceding unsigned comment added by 128.100.71.45 (talk) 19:26, 25 May 2010 (UTC)

Yes, they are capable of seeing unimaginable colors. The previous author is not talking about humans, for which tetrachromacy is a fluke, but animals, who use it functionally. The can perceive ultraviolet light, which humans cannot, and therefore, a color made from mixing red and ultraviolet will look completely different from the color red. Our brains are literally not wired to comprehend these colors, and trying to picture them is as futile as a red-green color-blind person trying to picture the color red. — Preceding unsigned comment added by 67.185.65.184 (talk) 09:06, 5 April 2013 (UTC)

## LSD use

I've heard of Individuals being able to see additional colors in connection with LSD use (apart from being able to see sound). This would disprove that a trichromat can not "imagine" a tetrachromatic colorspace. However there does not seem to be much research on LSD in connection with tetrachromacy. 83.64.17.44 11:16, 6 March 2007 (UTC)

This is intriguing as an ancedote, but is not solid enough to use as source material for the Wikipedia. Ken McE (talk) 23:59, 21 December 2007 (UTC)

## whaterver

I want tetrachromacy ! damm ! what do we guys get they don't , I want to lord it over them for once! somebody help me find something (other than what hanges twixt my legs ;-) that I have that they don't.

Hi, in exchange for lesser color vision men get better night vision. So go out tonight and enjoy it! Ken McE 21:42, 14 August 2007 (UTC)

Probably will be done one day as genetic engineering pick up pace. It wouldn't realy be a difficult thing to do, at least not on a one cell level. If done on a stem cell it could then be induced to develop into an complete organism. 130.243.153.103 16:48, 25 May 2007 (UTC)

Hi 130.243,

We don't know how easy or hard it would be. Just popping a new sensor in might work, or it might not. There are a lot of "ifs". The mouse study below is encouraging, but far from conclusive. If the new sensor was within the existing visual range you might just see the existing colors more precisely rather than see a whole new color. If the new sensor is outside the existing 400~800 nm range you would run into the issue of how to focus the new wavelength using our existing lens, which is optimized for our existing spectrum.Ken McE (talk) 01:47, 5 December 2007 (UTC)

First, you don't want the tetrachromacy gene, Ken. It'd probably make you colorblind. There are hard limitations to what the human eye will do. The lens and cornea absorb more and more light the lower you go in wavelength, becoming opaque by about 380nm. This is why we call colors beyond that ultraviolet. As far as I can tell, the upper biological limit is simply room on the lens and finding the right pigment (and space on our genome). Simply put, adding another receptor to boost our spectral range could easily lower our visual resolution. I would much rather take the green and yellow-green (green and red) receptors and use different pigments to spread their spectral responsiveness out. Then you'd reduce the red-green redundancy, gain spectral range, and probably cap out when you stopped being able to distinguish heat from the blood vessels inside your eye. ◗●◖ falkreon (talk) 10:24, 10 January 2011 (UTC)

Why should not some men be tetrachromats? It is evident that trichromacy in primates developed from dichromacy in the same way, with the females "going first" as it were, and the process still hasn't completed, with 99% of women having left dichromacy behind, but only 92% of men. Surely there is potentially a mechanism whereby human males can also be tetrachromats. I suspect that I am a tetrachromat and I am male. I have a lot of indicators such as complaining about the "wrong type of orange", the ability to perceive greenish orange (impossible in the 3 colour model), and being able to see a whole different range of hues from red through orange to yellow on an RGB monitor when the monitor's red emission is of a longer wavelength than typical. Regardless of the adjustment of saturation, brightness and contrast on the monitors it is not possible to match the rich oranges and yellows of the monitor that uses a long wavelength red when using the monitor with a shorter wavelength red. I am also very sensitive to the difference between flourescent lights and non-flourescent, and find it is lights that lack long wavelength red that are unpleasant. Whites of the same colour temperature do not match if one has a spectrum containing long wavelength red and the other doesn't. 132.185.144.120 (talk) 20:16, 20 December 2012 (UTC)

Just to throw a wrench in all this: we're all descended from tetrachomatic ancestors and still maintain a fourth psychological primary in the brain! It is synthesized from red and green as yellow. Because it's a synthesized primary it's not perfect, that's why we don't have colors like reddish green or greenish red, yellow gets in the way. A true tetrachrome might be able to see reddish green or greenish red as distinct from shades of yellow, but living in a trichrome dominated world they might not be conscious of it. 70.27.31.82 (talk) 14:57, 21 December 2012 (UTC)

The article says Tetrachromacy has not yet been discovered in any mammals and later says at least one tetrachromat has been identified - "Mrs. M" ... Is she not a mammal? Don Don 18:44, 31 March 2007 (UTC)

No: humans are glorious spiritual beings set apart from all the base creatures of the... uh, fine you're right, she's a mammal. Not sure how we should change the article to reflect this. I guess: "only one confirmed case of tetrachromatism has been discovered in mammals"  ??? Sound good?

No, it does not. It has not been solidly confirmed that she is a tetrachromat. Ken McE 21:44, 14 August 2007 (UTC)

## Tetrachromat Testing

Just wondering why no one has created a test similar to the Ishihara color test. It seems that the approximate maximum sensitivity of the fourth cone could be experimentally determined from perceptual studies on potential tetrachromats. These tests could be performed similarly to the experiments performed by Wright & Guild to formulate the CIE 1931 color space. Then, based on that wavelength, images could be created analogous to the Ishihara test images, in that some would contain symbols that only tetrachromats could distinguish. I know i am oversimplifying the issue, but it seems pretty straightforward. Straha 206th 22:44, 28 June 2007 (UTC)

Creating such a test would certainly be handy to help us find an actual tetrachromat. There is a problem in that we would need to know where their area of extra sensitivity is in order to print up the test. If we're just guessing we might have to print up a dozen or a hundred and hope to get lucky. Ken McE 21:50, 14 August 2007 (UTC)

Testing non-human organisms is going to be an interesting problem ! Existence of pigments in retina or plumage, or even colour sensitivity doesn't prove vision. Wouldn't the new wavelengths have to be focussed by the lens ? I suspect from the complexity of moth & mosquito antennae that they are pretty directional and wavelength-selective sensors for infra-red. Incidentally I am pretty certain I can see infra-red out to 850nm, from a time I was working with a tunable dye laser and spectrometer. I can also see a de-focussed halo around mercury vapour street lamps, presumably because partly-focussed UV (253.7nm ?) is causing fluorescence in my retina. Might these count ? Printing tests isn't going to be easy because we normally use '4-colour' printing. I know photo inkjets have more dyes, but you mght want to create new dyes ! Tunable light sources might be easier. If parrots react reliably to human-invisible patterns in mates' plumage, we could re-arrange plumage on a stuffed parrot so they look the same to us, but different in UV. Ishihara meets Monty Python ... --195.137.93.171 23:41, 7 September 2007 (UTC)

I believe some tests were done in this [1] experiment which suggested the lizards were tetrachromats (i.e. actual perception tests, not just the pigments are there tests). It may have also mentioned some other perception experiments Nil Einne 12:31, 9 October 2007 (UTC)
The Ishihara test may be useful. From my own experience, I see colors quite well, but I can't see most of the numbers on the Ishihara test. I just see a multitude of colors. This may relate to the fact that my father and son are color blind, so I carry some sort of anomaly. — Preceding unsigned comment added by Mamjean (talkcontribs) 03:23, 9 August 2012 (UTC)

An effective test would be to set up some coloured LEDs of known output frequencies (e.g. IR, red, yellow, green, blue, purple, UV) and cover them with a diffuser so that the colours merge into one. Having two sets you can get people to compare. Say one side you light up the red and green LEDs, the other just the yellow. Of course the outputs have to be balanced, so both sides are the same brightness, at least to a trichrome, but to a tetrachrome they might look different. 70.27.31.82 (talk) 15:08, 21 December 2012 (UTC)

I'd like to make a note that a google search for this is probably futile, as monitors were no doubt designed for trichromats. 74.64.80.193 (talk) 04:49, 12 January 2013 (UTC)
--195.137.93.171, there is some natural variation in human vision, even within the limits of just three color sensors.  It sounds like your vision goes about as wide as anything human can go.


Ken McE (talk) 01:57, 5 June 2017 (UTC)

## The Purkinje effect

Because most people have three colors of cones along with rods, isn't perceived color going to be inherently four-dimensional rather than three-dimensional? Isn't this exactly what happens in the Purkinje effect? —Ben FrantzDale 22:31, 9 July 2007 (UTC)

Yeah, sort of. But while there are four spectral sensitivities, there's little or no range where all four do anything useful. We're trichromatic in bright light, monochromatic in dim light, perhaps dichromatic in the mixed light of a dull camp fire (which can stimulate the L cones and not much more) and starlight (which can stimulate the rods). We don't have neural circuits to support true tetrachromacy. I'm not sure how the crossover region behaves; that would be a good thing to find a source on. Dicklyon 22:36, 9 July 2007 (UTC)
Sounds right. I've had this idea for a while and just now followed the Wikipedia rabbit hole. (The following will get mathy.) The way I understand it is this. Color out in the world is infinite-dimensional: a spectrum, with an energy density assigned to every wavelength, ${\displaystyle I(\lambda )}$. Assuming each of our receptors is linear, then the intensity detected by each receptor is determined by the color matching function, i.e., its detection spectrum. That is, if the color matching function for a receptor is ${\displaystyle F(\lambda )}$, then the detected value is
${\displaystyle \int _{0}^{\infty }I(\lambda )f(\lambda )\,d\lambda }$
which is just an inner product. That is, it's a projection from infinite dimensional space onto the "axis" defined by ${\displaystyle f(\lambda )}$. As such, it seems natural to consider color for most people to have four channels, even if the channel provided by the rods is hardly orthogonal to the other three. —Ben FrantzDale 02:17, 10 July 2007 (UTC)
Yes, that's all pretty much right, except that the f(lambda) are not the CIE XYZ color matching functions, but rather the cone functions. And the detectors don't need to be linear, they just need to have a linear first step, which is that inner product. The nonlinearity becomes important when you realize that for the cones to be responding much above their noise floor, the rod signal will be saturated. Thus the 3D cone subspace works for color at moderate to bright levels, and the 4D subspace, which is well defined, has little role in perception. Orthogonality is not very relevant, since none of them are (S and L are nearly orthogonal, though, I suppose). Dicklyon 04:01, 10 July 2007 (UTC)

## Birds

I don't really know much about bird gender and genetics, but I was wondering if the possibility of tetrachromacy is reserved for human women, is it the same in other animals and insects. In the case of birds, it would add another dimension to the high sexual dimorphism, specifically, male plummage. Now that their finding even more difference that were previously undetectable in the human spectrum of sight in birds feathers, are these difference just for the females?71.235.115.115 03:33, 19 July 2007 (UTC)

No, birds have different kinds of sex chromosomes. Females are ZW and males are ZZ. If they did have sex chromosome linked color genes, you would expect more deficiencies in the females than the male. 70.27.31.82 (talk) 15:22, 21 December 2012 (UTC)

Humans are designed to be trichromats. Some people *might* get an extra color by mistake, due to the details of how our genes work. There are animals that are designed to get more (or less) colors than we do. It is standard equipment for them, not a mistake. There could be species where males and females have vision that varies even more than ours does. I don't know if it has been studied. Ken McE 21:54, 14 August 2007 (UTC)

It's not really correct to say humans are *designed* to be trichromats. Early Mammals, originally descended from tetrachromats, lost two chroma to become dichromats, then later early Primates had evolved a third chroma around the red. 70.27.31.82 (talk) 15:22, 21 December 2012 (UTC)

(Crossposted reply) - Birds are tetrachromatic having cones for the red, green, blue and UV regions of the spectrum. As far as I am aware there is no widespread sexual difference in colour perception in birds. The signals you dexcribe that they can percieve but we can't are UV in nature but are used for signalling to both species. I'll amend the article to include mention of tetrachromacy. An interesting subject we allude to without directly mentioning. Sabine's Sunbird talk 04:25, 19 July 2007 (UTC)
• Addendum - Tetrachromacy has not yet been confirmed in any animals, though it is expected to occur in some birds, fish, amphibians, reptiles, arachnids and insects. - Uh, birds are tetrachromatic, they have the UV cones as well as the 3 colour ones. [2] Sabine's Sunbird talk 04:28, 19 July 2007 (UTC)

## Possibility of human tetrachromats

The last paragraph in this section suggests that the extra information from an additional cone would get muddled in the brain, but recent studies (see link for article) with genetically modified trichromatic mice show that they are able to select a colored panel for a treat 80% of the time compared to 1/3 of the time for the control mice. I believe this shows a flexibility of the mammalian mind that could allow a tetrachromatic human to fully utilize the extra information. Further more, I recently watched the movie "in pot we trust" which features a San Diego police officer with an extraordinary ability to distinguish between shades of green, allowing him to spot marijuana plants from a helicopter. I believe it is possible that he is a fully functioning tetrachromatic.

http://www.physorg.com/news93792566.html �Preceding unsigned comment added by 71.160.237.237 (talk) 17:15, August 29, 2007 (UTC)

Hi 71.160,

I meant to suggest that it is difficult, not that it is impossible. We know that it is biologically possible, we just don't know if *we* could handle it.Ken McE (talk) 23:51, 21 December 2007 (UTC)

I agree with 71.160.237.237, The Difficulties section seems out of place. The other sections read well, and contain references, whereas this section seems tacked on. A section about the supposed difficulties in our own physiology should be backed up by some professional expertise. If it is based on a study of some sort, could it be referenced? If it is put on to emphasize the uncertainty of human tetrachromats, could it be reworked to work more organically with the rest of the article, or expanded so that the section has more substance? Skp2y F thorax (talk) 01:28, 4 March 2008 (UTC)

You are correct that the difficulties section was added on after the rest of the article. It stays with things that are very simple and basic in the hope that it will be easily understood. I don't like to throw cold water on the idea of humans with supervision, but accuracy trumps my personal preferences. It would be a bit difficult to add references to studies and authorities, because there almost aren't any. Vision is still not well understood. Changing vision in a purposeful way is mostly science fiction at this point in time. The intent of the section was precisely as you say to "emphasize the uncertainty of human tetrachromats". If you can make it a bit more graceful, a bit more organic, please feel free to do so. Ken McE (talk) 23:01, 14 March 2008 (UTC)

I find the problem with the "Difficulties" section to be as follows: it posits the arrival of tetrachromacy as an ADDITION to an already existing brain / nervous system (with words such as "it is not clear if the nerves could handle the extra channel"). For a person born with this condition, there would be nothing extra -- the brain and nervous system would have been presented from the very first moment with 4 different signals. Since it is not clearly understood how the brain makes sense of the three signals it receives in normal trichromatic vision, it seems somewhat limiting to assume that the brain of a tetrachromat could not make sense of the extra sensory input. WikiDan61ChatMe!ReadMe!! 18:43, 22 April 2009 (UTC)

Hi WikiDan61, Consider an analogy: I manipulate an embryo so that it will be born with an extra finger. It will have that finger from birth, but unless it has muscles and nerves to use it with, and a clear connection to the brain, it will just hang there uselessly. Just gluing on an extra finger is not guaranteed to make it functional.

We know that nature practices parsimony in design, and this suggests that the optic nerve is sized just about as small as it can be, and still handle its workload. What happens if you leave the nerve the same size, but try to run through 25% more traffic? Mice or no mice, I'd say we don't know.

Ken McE (talk) 21:45, 27 November 2009 (UTC)

Ken: With respect, there is a concept that you have not considered that may be relevant. Have a look at it here: Neuroplasticity. Old_Wombat (talk) 04:23, 12 March 2011 (UTC)

## Tetrachromats and RGB monitors

The question I find fascinating, that I have seen no research on, is this: since RGB monitors present information approximately mapped to a human's three color receptors, how does a tetrachromat's perception of RGB colors vary from a trichromat's. For example, if a screen is displaying a yellow image, there are red and green pixels lit. There is no actual yellow light, but the trichromat's receptors are stimulated in the same proportion as they would be if pure yellow light were presented, and the person perceives yellow. However, the screen ONLY stimulates the tetrachromat's red and green receptors, and not the intermediate (orange?) receptor in the same way that the pure yellow light might, so does the tetrachromat perceive the image as something other than yellow? If so, this must make the world of computer imagery (and televison and three-color printing, etc) truly maddening to such people. WikiDan61ChatMe!ReadMe!! 18:43, 22 April 2009 (UTC)

Use a monochrome display and you will understand. Czech is Cyrillized (talk) 06:49, 14 September 2013 (UTC)

## Basic colours

For trichromats, there are 2^3=8 basic colours: black, red, green, blue, cyan, magenta, yellow and white. But for tetrachromats, there are 16 basic colours. Let's name the extra colour octarine. The extra basic colours for them are: octarine, octarinish red, octarinish green, octarinish blue, octarinish cyan, octarinish magenta, octarinish yellow and octarinish white. second that — Preceding unsigned comment added by 157.193.9.140 (talk) 11:56, 28 July 2011 (UTC)

You can't count that way. The cones register colour but rods register light or the lack there off. Therefor black and white (more correctly darkness and lightness) should not be counted as basic colours. When a trichromatic eye sends a signal to the brain, it uses 3 scales, light-dark, red-green, blue-yellow, the human brain then makes an 3D colourspace based on those 3 axis. The bw rgb cmy is a misinterpretation of what colour is. Colour is a wavelength or a combination there of. Normally humans can register 300 different wavelengts, each of which is a basic colour. The number of combinations possible is larger than the human eye can see, and many combinations even thou they are very different will be percieved as the being alike by humans. Red green blue are primary colours in a coloursystems where colours are made by adding light. Cyan magenta yellow are primary colours in coloursystems whre ligth is being taken away. balck and white are not colours. Colour systems made up by 3 components are never able to make all the colours a human can percieve.

A light source sends out up to 300 differnt wavelengts, that are reflected into a human eye. The eye registers lightness, red, Green and blue, and send a signal to the brain in form of a 3D coordinat on the axis red-green, yellow-blue, dark-light, the brain a colourspace and interprets colour by a way simular to longitude, latiude and distance to the core, the brain then associate the colour to a memory or feeling. The interesting part is not only which wavelenghts a fourth cone may register, but also how they are signaled and percieved by the brain.94.145.236.194 (talk) 16:51, 25 September 2011 (UTC)

The orange receptors will be stimulated along with red by the red emission, because all the sensitivity curves are broad. The difference will be how red the red looks, or what shade of red it is, which will depend upon where the peak wavelength of the red emission lies with respect to the peak sensitivies of the tetrachromat's orange and red receptors. 132.185.240.124 (talk) 21:21, 20 December 2012 (UTC)

## Left and right eye variations

I assume that the left and the right eye do not have rods and cones with the same response to wavelength. (Sensitivity is certainly not always the same.) In that case, it's possible, isn't it, that humans can see six primary colors, or including the greyscale possibilities discussed above, eight?

Piano non troppo (talk) 07:09, 16 September 2008 (UTC)

## Discrepency?

Is there a discrepancy betweeen the several statements in the article which treat the human tetrachomatacy as an unconfirmed hypothesis:

Further studies will need to be conducted to verify tetrachromacy in humans. Two possible tetrachromats have been identified [...]
It is possible that some humans could have four rather than three color receptors.

and the one near the end which seems (to a lay reader, at least) to treat it as an established phenomenon:

People with four photopigments were shown to have increased chromatic discrimination in comparison to trichromats.

...or am I missing something here? Dependent Variable (talk) 21:13, 26 September 2008 (UTC)

Hi Dependent Variable,

Different people come in with different standards and this affects what they write. Every time I try to track down any reported human tetrochromat to a reliable source I end up with a speculative piece in some small town newspaper. This causes me to put in qualified statements like those at the beginning of your question. It is possible that other Wikipedians have sources that I have not located, sources that present arguments for more definite statements. This would be good reason for them to put in the stronger statements.

The "People with four photopigments" quote goes back to link six of the article. Link six goes to a PDF titled:

Richer color experience in observers with multiple photopigment opsin genes by: KIMBERLY A. JAMESON and SUSAN M. HIGHNOTE, University of California at San Diego, La Jolla, California and LINDA M. WASSERMAN, University of California at San Diego School of Medicine, La Jolla, California

If you work through that article it does state:

"These results suggest that perceptual color experience for heterozygoes females is more articulated than is color perception for “normal ” trichromatic subjects." This suggests keen color discrimination, but is a far cry from claiming that they see any more or different colors than anyone else. Ken McE (talk) 03:01, 4 July 2010 (UTC)

## No functional female tetrachromats found among humans. Unlikely sexual dimorphism among birds but never male-biased defective color perception

It's very unlikely women with two gene sets encoding for photoreceptor pigments with a different wavelength responsiveness for each set can ever take advantage of such trait. The explanation grounds in two facts. Women are not heterozygotic for most of the X chromosome genome at the cellular level. Instead, they are mosaic, i.e., only the genes present in the major part (including the genes encoding for the pigments) of one of the two X chromosomes will be expressed in every single cells. This is not enough to explain my assertion as in any cone cell only one of the different pigments are already expressed, and even so, the color sensitive mechanism is able to integrate the information coming from different color-specific cone cells to resolve the wave length that excited to those cone cells. The main problem is the way in which most of the genes present in one of the two X chromosomes are inactivated in every cell. In most mammals during the development of the embryo one of the X chromosomes is inactivated at random in every cell (under normal conditions). All the descendants of the these cells will inherit the same inactivated X chromosome. Usually this inactivation is permanent. That gives rise to a distribution pattern in most solid tissues in which cell patches share the same inactivated X chromosome, all those cells derived from the same embryonic cell. The whole tissue is a succession of patches in many cases of macroscopic size. Thus, there's no use of having two different pigment sets if all the neighbor cone cells around just express one pigment of always the same the pigment set, that is, the pigment set encoded in the X chromosome that escaped the chromosomic gene inactivation. Only in boundary regions between patches could be integrated the information provided cone cells expressing pigments of the two sets. The only way to achieve a functional color discrimination would be that the retina cells coming from different early progenitor cells being well mixed to reach a similar cone cell proportion for each different pigment in every tiny photosensory area of the retina.

Birds are unlikely to have sexual dimorphism for the color perception because sex chromosomes have evolved separately in mammals and birds, thereby, most genes present in the X chromosomes are not found as homologue genes in the bird sex chromosomes. But what makes almost impossible to occur is to find a male bias for a sex-linked recessive disorder since in birds the heterozygotic for the chromosomic sex determination is the female. Bird females are WZ whereas males are ZZ. If there's a gene mutated in the Z chromosome and the mutation is recessive it is more likely that the affected individuals be females since they just have one Z chromosome and therefore, only one copy of the gene (if there's just one copy of this particular gene in the haploid genome). Interestingly, in birds two sets of genes in the Z chromosome coding for different pigment sets could increase the effective color discrimination in males since in birds there isn't Z chromosome inactivation. Instead the genes of both Z chromosomes are downregulated to compensate the gene expression dose with the female gene expression (alternatively it can be said that the genes present in the female single Z chromosome are upregulated to reach the same dose as in males). Heathmoor (talk) 01:16, 30 October 2008 (UTC)

As far as I've found in my search, the exact mechanism for photoreceptive pigment determination in cone cell remains elusive to date. While in some species the pattern of distribution has to be forme by a random process (for instance, in chimps), in others seems not to be the case (notably, in humans). Furthermore, in humans there's a huge variation in the ratio respect to the three types of cone cells present in the retina among the few human individuals in which this pattern has been studied to date. Despite of this, there are very little differences in the perception of color between them. This seems to becaused by the means in which the perception of color is calibered in the brain, relying this in a major extent in the visual environmental inputs received during the day. For further reading go to the David Williams' Lab web page section research with some documents about this topic:
http://www.cvs.rochester.edu/williamslab/research.html
In paricular:
http://www.cvs.rochester.edu/williamslab/r_trichromatic.html
http://www.cvs.rochester.edu/williamslab/r_retmosaic.html
http://www.cvs.rochester.edu/williamslab/r_colblindness.html
As well as the related articles:
http://www.jneurosci.org/cgi/content/abstract/25/42/9669
http://vision.berkeley.edu/roordalab/Pubs/ROORDA.PDF
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WSS-4CC2Y75-32&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=efe3f127e879cd0e7a2d17dfe3da250d
That's all I've got so far. I hope someone will shed some light on the process by which cone cells are determined to produce a specific photopigment and the way these cells become spatially distributed along the retina --Heathmoor (talk) 04:11, 15 January 2009 (UTC)

In addition, it can be related to tetrachromacy the fact that actually the human eye is already tetrachronic when we take into account the additional photopigment found in glial cells in the inner retina. This photopigment has a different molecular structure what leads to a different pattern of light response. It's been known for some twenty years. It's been previously thought to be exclusively associated to the regulation of the endocrine system and with no connection to the visual input processing. However, recent studies have found that the signal generated by the specific stimulation of this glial cell photopigment seems to be perceived by the central nervous system at the conscious level. This trait opens the question on a possible role of this pigment in the perception of color.
For further reading tyou can find some information and references in the WIkipedia article Photoreceptor cell and additionally, you can consult some specialized publications such as:
http://www.cell.com/current-biology/fulltext/S0960-9822(07)02273-7?large_figure=true
Heathmoor (talk) 05:41, 15 January 2009 (UTC)

## Dicklyon

Stop reverting my edits unless you got a sufficient knowledge on such things as spectral colors and chromaticity. For 3chromatic vision we can match any given chroma by a mixture of two chosen waves, and can make it in infinitely many ways (1-parametric family, because one degree of freedom is spare). But you can not find such three fixed waves which can match all chromas (even in trichromatic vision), you can not obtain a full gamut even by any finite number of fixed waves. Incnis Mrsi (talk) 09:45, 27 January 2009 (UTC)

As it happens, I am an expert on colorimetry and color vision and photography. I re-editted this bit to make the intended meaning more clear. It's true that you can make an arbitrary color from two specially chosen monochromatic colors, but I think that's not the kind of point that was intended there. Dicklyon (talk) 18:01, 27 January 2009 (UTC)
Yes, I also thank that it's 3-dimentional chroma (instead of 2) the essential property of tetrachromatic vision, but not imaginable experiments with matching colors using monochromatic lights. That's why I removed the statement, but you considered it as my mistake. Incnis Mrsi (talk) 19:24, 27 January 2009 (UTC)

Also, have your some sources stating that Susan Hogan is a physician[3]? Even if this is true but such fact in not publicly known, then it must be removed (WP:BLP). Incnis Mrsi (talk) 14:02, 27 January 2009 (UTC)

I don't know anything about her. Oh, I see, you're referring to my revert of an uncommented change of physician to interior decorator. If that was you, and it was serious, be aware that an edit summary will go a long way to distinguishing such an edit from drive-by vandalism. Dicklyon (talk) 18:01, 27 January 2009 (UTC)
No, I never visited England and do not use proxies in casual Wikipedia edits ☺ Incnis Mrsi (talk) 19:24, 27 January 2009 (UTC)

## Difficulties section

I tried to make it flow a little better; this did unfortunately involve moving some of the text around. I tried to keep the meaning intact, but as someone who has no expertise in the field it would appear from Piano non troppo's revert that I got it hopelessly wrong. Would someone who does know about the subject mind looking at it? - Jarry1250 (t, c) 10:06, 18 February 2009 (UTC)

## Rods and Rhodopsin

The article states that "Rods may help with color vision in low light situations" but doesn't cite its source. Rods, and their photopigment rhodopsin, can't distinguish color. It's a binary pigment. Either light is or is not when it comes to rods. I'm going to remove the line. If anyone can prove me wrong, cite your source first before adding in the information 147.124.150.164 (talk) 15:01, 30 April 2009 (UTC)

I added a source; feel free to investigate further and expand or whatever. Rods are not "binary"; like cones they have their spectral sensitivity curve, which can help distinguish things of different colors, perhaps, when both rods and cones are active. Dicklyon (talk) 22:20, 30 April 2009 (UTC)

Bit of loose definition here that causes the confusion. Yes, rods have a spectral sensitivity curve, but the ONLY thing that that means is that objects that are different colours under bright lighting will appear to be different shades of grey under dim lighting. So, IF you knew beforehand what colour various otherwise identical objects are (i use plastic clothes pegs for this purpose), you could then intellectually DEDUCE which of them is what colour under light too dim to actually see the colour. However, that would not help you at all in determining the colour of an unknown object that you then looked at in dim light. Whether or how this may or may not fall under the scope of "distinguish things of different colours" is beyond my ken. Old_Wombat (talk) 04:40, 12 March 2011 (UTC)

## Difference between several articles

On the article http://en.wikipedia.org/wiki/Orange_(colour)#Medically it states:

"A woman named Susan Hogan was born with an extra set of cones that are sensitive in the orange range, as well having the red, green, and blue cones that humans with normal colour vision (i.e. trichromats) possess. She is therefore classified as a tetrachromat, but her extra type of cone is an orange cone instead of the ultraviolet cone possessed by animals such as birds who are tetrachromats in nature. It is estimated that while normal humans can see about 1,000,000 different colours, tetrachromats such as Ms. Hogan can see 100,000,000 different colours. This is because each additional type of cones interacts with the other types of cones in such a way that an addition of a new type of cone means an organism can see 100 times as many colours. (This means that a pentachromat would be able to see 10,000,000,000 (ten billion) different colours.)"

"Two possible tetrachromats have been identified: "Mrs. M," an English social worker, was located in a study conducted in 1993,[7] and an unidentified female physician near Newcastle, England, was identified in a study reported in 2006."

The first gives more information about Tetrachromacy than the Tetrachromacy article, (i.e. "each additional type of cones interacts with the other types of cones in such a way that an addition of a new type of cone means an organism can see 100 times as many colours"), however the Tetrachromacy article implies that "Susan Hogan" doesn't exist with "Two possible tetrachromats have been identified". I am no expert on the subject (if I was I would just correct it), but could someone who knows more about the subject make the correct alterations? --pc (talk) 22:49, 18 August 2009 (UTC)

The Wiki articles should be changed to agree.
Let me adopt a position here for the sake of discussion? For various reasons, I tend to believe that tetrachromacy exists in humans. The case of "Susan Hogan", however is not admissible as Wiki evidence. The description in Orange is from a single article in a general newspaper, describing the theory of a single doctor. If the newspaper article description is correct,[4] then Jordan's experimental process is suspect -- it is suggestive, but hardly conclusive.
In terms of correcting discrepancies, downplaying "Susan Hogan" and the unsupported interpretation of limited tests might be helpful. The experiment is suspect, and her situation apparently unique. (Deleting the material from Orange might be appropriate.)
This statement in the current Wiki article is crucial, and could be expanded upon:
"It is not known how these nerves would respond to a new color channel, if they could handle it separately or would just lump it in with an existing channel. Visual information leaves the eye by way of the optic nerve. It is not known if the optic nerve has the spare capacity to handle a new color channel. A variety of final image processing takes place in the brain. It is not known how the various areas of the brain would respond if presented with a new color channel."
I worked with someone who did color adjustment for magazine publication. Although I have normal vision, he constantly criticized my color-matching ability. With the greatest of difficulty, I could bring myself to believe there was a color difference between two very close samples he showed me. I draw a conclusion from this: Regardless of my quite theoretical ability to distinguish millions of colors, I can't in practice distinguish between many of them. Furthermore, I'd be completely unable to identify them subsequently, or to put a name to them. So the question is: how do these extraordinarily huge numbers of theoretical colors affect the practice of perception? Piano non troppo (talk) 02:21, 19 August 2009 (UTC)

Hi Piano, I followed your link over to the "Susan Hogan" section in the Orange article. It is full of lovely speculation but I couldn't trace it all back to anything more authoratative than the popular press. I deleted Ms. Hogan. We'll see if she comes back. Ken McE (talk) 15:24, 25 December 2009 (UTC)

## Animal Model

This nature paper and the associated news coverage seems to demonstrate that color blind monkeys were able to gain trichromacy by inserting a gene. Since the brains adapted and were soon able to process the new signal, it provides some evidence that the section on 'Difficulties' may not be as difficult as initially supposed. Cariaso (talk) 19:27, 20 September 2009 (UTC)

## Some tetrachromat humour

Look, all of this human tetrachromat discussion is very serious and unfortunately somewhat heated, so here's some humour to attempt to lighten the tone (and no, I am NOT proposing including this in the main article!). At a lecture on colour vision by Professor Stephen Dain, who was then head of the School of Optometry and Vision Science at the University of NSW, he made the comment that tetrachromats can only be female. This led to the interjection that "this is why women, but not men, can tell the difference between 4000 shades of pink lipstick". Old_Wombat (talk) 04:16, 12 March 2011 (UTC)

## "The Human is a Blocked Tetrachromat"

At the end of the article is the link

• The Human is a blocked tetrachromat A review of the spectral sensitivity of the human visual system. (Suggests that the human lens is responsible for blocking the ultraviolet frequencies, that we already have a UV sensor in the retina ready and waiting, and if the UV wasn't blocked, we'd all be tetrachromats.)

But it seems to suggest that people who have this ability merely see ultraviolet light as violet (and for the very shortest wavelengths, white), so it's not really a "fourth" channel, it's just a wider range of sensitivity to violet light. Soap 12:28, 11 June 2011 (UTC)

The problem with that link is that there is no evidence for a UV opsin being expressed in anyone's cone cells. The only known/suspected human tetrachromats are based either on a mosaic of the two alleles of the MW (green) opsin or the LW (red) opsin. [5] Most human tetrachromats are thought to be based on having two different greens, ie, two alleles of the MW cone opsin, or two different reds (LW opsin), on their two X chromosomes. No human UV opsin is known to exist. My own theory for the observation that being an X-chromosome-based mosaic of two similar opsins does not usually result in actual tetrachromacy is that, for functional tetrachromacy, the different opsins have to be expressed in cone cells that can be distinguished by the visual cortex as having distinct spike rates. This is an alternative to the suggestion in the Pst Gazette story linked above, that the peak wavelength isn't usually sufficiently different. DJMcC (talk) 11:27, 11 September 2012 (UTC)

An objective measurement of human tetrachromacy would be to use a tunable monochromator to identify the wavelengths that the subject considers to be the centres of "qualitatively different" colours. This could be compared with the standard "ROYGBIV" rainbow, with the known typical values for eight colour bands. (After adding turquoise, as transitional between blue and green in the same manner as orange is transitional between red and yellow.) The "dirty" colours of non monochromatic colour patterns are a complication to be avoided in an objective test. Of course, it can always be argued that every colour is transitional between its neighbours in the spectrum, and there will always be some room for subjectivity. I also suspect that there would only be certain wavelength bands where extra rainbow colours exist, because the wavelength split between the two greens, for example, is only 5nm, compared with at least 30nm for the red/green split of a standard trichromat [6]. As a result, the most visible changes in tetrachromacy should be away from the "RGB" wavelengths. It must be noted, however, that the exact cone firing response curves are shifted from the opsin absorption curves shown in the above links, mainly due to the absorption spectra of other elements of the retina. DJMcC (talk) 12:25, 11 September 2012 (UTC)

btw if human can see uv (aphkiac ones) then we'd all be tetrachromats and red-green color blind men will be trichromats and women that have super color vision will be pentachromats? 109.174.115.127 (talk) 06:44, 24 January 2013 (UTC)

Do you read what other people says? Aphakia and other means to expose the retina to UV have nothing to do with tetrachromacy. It is only an extension of the visible spectrum. Incnis Mrsi (talk) 09:03, 24 January 2013 (UTC)
Imagine if humans can see uv, then they will see vivid violet then whitish blue after visible violet color, there will be 9 colors in rainbow and we should call those uv colors such as septarine and octarine thus our color system would be RGBV and we will see 100 million colors compared to trichromatic 1 million colors and dichromatic 10,000 colors 109.174.115.255 (talk) 09:33, 1 March 2013 (UTC)

There is evidence for a UV opsin in humans, with an absorption peak at 380 nm. "UV-sensitive photoreceptor protein OPN5 in humans and mice", Kojima et al, 2011. [7] D.keenan (talk) —Preceding undated comment added 05:02, 8 September 2016 (UTC)

From that ref, it appears to be not in the visual system, and probably unrelated to potential tetrachromacy. Dicklyon (talk) 06:16, 8 September 2016 (UTC)

## news

http://www.dailymail.co.uk/health/article-2161402/Gabriele-Jordan-British-scientist-claims-woman-superhuman-vision.html — Preceding unsigned comment added by 76.172.122.94 (talk) 08:59, 19 June 2012 (UTC)

## Question about the meaning of the Insects section

Could: Floral colors were categorized into two main wavelengths of light including 360–520 nm and 400–500 nm. be changed to: Floral colors are categorised into two main wavelengths ranges of light: 360–520 nm and 400–500 nm. Thanks for helping me understand. Edouard Albert (talk) 19:02, 15 November 2012 (UTC)

I don't know about that specific research, but saying "ranges" is certainly more correct grammatically. I think this is non-controversial enough that you could just go ahead and do it. My opinion is that the section is very confusing and has no structure. There's no flow and the lead sentence doesn't help the reader help understand what the section will be about. Jason Quinn (talk) 23:57, 15 November 2012 (UTC)
Many thanks Jason. I've tried to simplify the whole section keeping references. Please revert if any worse, and be kind if I made mistakes. Edouard Albert (talk) 13:37, 18 November 2012 (UTC)

## Sexism?

Why are females being considered the only gender that Tetrachromacy can occur in? it occurs on the X chromosome, therefore men can have it, period. Bumblebritches57 (talk) 00:53, 9 September 2013 (UTC)

Well, I don't think it's that simple, but I agree that this article does a terrible job wording the explanation of why only females can be tetrachromats. --WikiDonn (talk) 22:53, 9 September 2013 (UTC)
No, it is not that simple, since some genes need to copies to express themselves. And some traits require two different copies of the same gene on the two chromosomes which is the argument for why it would be likely to 3occur only in women.User:Maunus ·ʍaunus·snunɐw· 23:01, 9 September 2013 (UTC)
you have a point about the multiple gene copy thing, but if there are males with it (as the page says 8% of men have it) it simply can not be limited to genes solely on the X chromosome. Bumblebritches57 (talk) 06:43, 11 September 2013 (UTC)
Well, most traits are polygenic and tetrachromacy probably is too. I haven't read the genetic studies of tetracromacy, but that would be the place to start to get the explanations. In any case who ever wrote it is probably just summarizing the claims of the literature, and there is nothing inherently impossible in the trait being more common in women. We'd have to read the sources to see how they explain it.User:Maunus ·ʍaunus·snunɐw· 10:18, 11 September 2013 (UTC)
There are people that we identify as men who have more than one X chromosome; similarly there are people that we identify as women that are "genetically male" -- sex determination relies on the activation of particular chromosomes or parts of chromosomes, and the path through development a fetus takes (which can be influenced by external factors). Women are more likely to have two distinct "red cone" genes because they have (almost always) two X chromosomes. Men are unlikely to do so because they have (almost always) one X chromosome. I can imagine that there might be quintichromats -- a woman with four X chromosomes that carry distinct genes associated with cones. Such people would be very, very rare though. Human genetics (and probably the genetics of most animals) is a lot more complex than we were taught as youngsters.

## X INACTIVATION AND TETRACHROMACY

IF A PERSON, LIKE MYSELF, WHO COMES FROM A LONG LINE OF MOSAICS, WITH AB CIS BLOOD AND TETRACHROMACY, RECOMBINATION OF CHROMOSOMES WITH X INACTIVATION, COULD PRODUCE SOMEONE WITH AN EXTRA RED CONE AND SOME ABILITY TO SEE INFRARED. ----REBECCA LUNSFORD ANDERSON — Preceding unsigned comment added by 68.7.130.72 (talk) 00:53, 15 January 2014 (UTC)

## cultural elimination possible?

I raise this because it seems to be absent from the article and this talk page, but I have no source. Perhaps someone knows if I'm wrong about this or knows where a source might be found.

I suspect the number of what I'll call conversational tetrachromats is a very small fraction of what I'll call retinal tetrachromats. That is, I suspect, for almost all tetrachromats, the retinas perceive into the usually-invisible ultraviolet range but the people with those eyes do not think they see into that range and would not acknowledge it in their conversations with anyone else, including other tetrachromats. I suspect this would happen because from early childhood on they would hear from other people about what is what color and which things have the same colors and almost all tetrachromats would coordinate what colors they think they see with what colors they are authoritatively told are present, the better to get along with other people and thence to gain personal power and succeed in life. (Sometimes, a child sees the sky as green.) With the cultural exposure to and influence of indirect color representations in media such as movies, computers, cell phones, and photography, none of which consistently display into the fourth range (monitors that allegedly display billions of colors probably are not manufactured to or tested for anything like precision for the fourth range and the 32-bit (4-byte) computer color scheme is really limited to 24 bits for actual color and 8 bits for degrees of opacity), social reinforcement that there's no color to see in the UV range would be even more common. Exceptions would likely be children whose parents, at least one per child, are also tetrachromats who willingly converse about what they see given four ranges; and children who grow up as outliers, perhaps becoming visual artists, gardeners, or specialists in fields where tetrachromacy is useful or where believing they see in the fourth range wouldn't be held against them.

Analogy: I understand that babies in the first few months of life are confused by our voices because they hear echoes and it takes those months to learn to ignore the echoes. We're so good at ignoring them that it now takes an extraordinary echo for us to recognize it, as in music with a specially produced echo.

When I was around 12–14 years old, I periodically was taken to a high-end department store, where a certain sales representative would wipe lipstick on the back of the customer's hand and proclaim it too "blue". The customer seemed to agree. I had no idea what they were talking about (they didn't ask me), since the sample was always obviously red. Later, I assumed what was meant was that the exact shade of red when applied to someone's skin leaned slightly toward the blue end of the spectrum, not that it's pure blue (like when astronomers and physicists talk about blue-shifting (the opposite of red-shifting)), and that the sales rep and the customer were just being sensitive to the precise shading of red. Now I wonder if the sales rep actually was perceiving into the UV range and saw some of it in the smeared lipstick, raising a question about the product manufacturing processes where product color matters. And, since she was working there a long time, I assume she was successful at sales, so, if she was a tetrochromat and influenced by it, she managed her skill well and maybe no one noticed except her happy sales manager. I wonder if a lot more cosmetics sales reps also perceive some reds as too "blue" not as physicists would (leaning toward blue) but due to tetrachromacy (strongly partly blue).

Nick Levinson (talk) 19:41, 2 May 2015 (UTC)

UV is my error, above. I'm told by Kimberly Jameson in an email that the fourth range is in or near the reds (if I understand correctly), at least that it's not UV.
I now think almost no tetrachromats conversationally distinguish the fourth range, but instead almost all have, since babyhood, been perceiving colors as trichromats do, because they're trained that way using pictures and what grownups persistently say. Conversational tetrachromacy being rare is probably supported by the absence of any support from almost any business, especially businesses with customers who are almost all women and which depend on color perception for customer satisfaction, since most would be happy to expand their sales by 2% by carrying products for tetrachromats and staffing with a tetrachromat and advertising it, but they don't, so the incidence of conversational tetrachromacy among adults and adolescents is likely extremely rare.
Nick Levinson (talk) 01:02, 14 July 2015 (UTC)

## "Possibility of" human tetrachromats? -> Aren't there confirmed cases?

So I'm wondering why that section is called "Possibility of" human tetrachromats? Isn't the section naming a confirmed case already? And AFAIK there are other cases which aren't mentioned there such as Concetta Antico.

and change that section's title and content as appropriate. --Fixuture (talk) 23:01, 2 May 2015 (UTC)

## Up to 8% of males have tetrachromacy is absurd. It's incredibly unlikely to be more than 1% of males

Used the value 3,790,000 as male population which is slightly larger than actual population. This will skew my results and give me a larger percentage of males with multiple X chromosomes. - 3,790,000/500=7,580 in higher population estimate and 3,000,000/500=6,000 in lower population estimate.

Types of males with multiple X chromosomes are XX, XXY, XXXY/XXYY, and XXXXY. Supposedly XXXXXY is possible but couldn't find any known cases or frequency related to male births.

For types that have ranges for birth frequencies I'm using the end of the range that will result in the most amount of males with condition. This will produce a higher number of males with multiple X chromosomes. Ultimately this will mean I will end up with the highest possible number of males with multiple X chromosomes. - If frequency is 1 in 10 to 100 births, 1 in 10 would be 3,790,000/10=379,000 males while 1 in 100 would be 3,790,000/100=37,900 males.

XX males - 1 in 20,000 to 25,000 births or approximately 189 males - 3,790,000/20,000=189.11

XXY males - 1 in 500 to 1,000 births or approximately 7,580 males - (3,790,000-189)/500=7,579.62

XXXY/XXYY males - 1 in 17,000 to 50,000 births or approximately 223 males - (3,790,000-7,580-189)/17,000=222.484

XXXXY males - 1 in 85,000-100,000 births or approximately 45 males - (3,790,000-189-7,580-223)/85,000=44.494

Total number of males with multiple X chromosomes are 8,037 males - 7,580+223+189+45=8,037

With a male population of 3,790,000 theoretically the most amount of males with multiple X chromosomes would be 8,037. This does not mean each one has tetrachromatic vision. Only that each individual has the potential to have 2 cones on 2 different X chromosomes giving them a total of 4 cones. However even individuals with 4 cones still don't always have tetrachromatic vision.

For the purpose of this demonstration let's imagine there's actually 10,000 males with multiple X chromosomes in a population of 3,790,000 males. This would mean that the percentage of males to possibly have tetrachromatic vision in the population would be at best .27% - 100/3,790,000*10,000=0.236852%

Basically it's absurd to think that up to 8% of males could have tetrachromatic vision. — Preceding unsigned comment added by 66.87.80.157 (talk) 08:39, 24 March 2017 (UTC)