Colourblind people: evolutionary advantage?

[Broomstick]

Originally Posted by Snnipe 70E

I doubt that there are many color blind pilots. I would think that being color blind would disqualify them.

I don't know about the military rules, but among civilian pilots in the US there are thousands of them, actually most likely in the five digits, because the US rules allow pilots with several types of colorblindness to fly. When I went to take my lightgun test the gent testing me said he'd had about 10 other women show up over his career for the same test, which given how small a percentage both women in aviation and colorblind people are is pretty interesting. He'd seen hundreds of male applicants for the test, most of whom apparently passed without much problem. The test is pretty straightforward, you can either do it or not.

Even the "opes" are allowed to fly in the US, they just aren't allowed to fly at night or in situations where light signals are used. So they're restricted, but not barred. I know there are some out there flying because I've met them.

If 8% of pilots in the US are colorblind that would be about 60,000 colorblind pilots. 8-9% is the rate in the general population, not sure if that would apply to US pilots or not.

[Broomstick]

Originally Posted by thelurkinghorror

Thanks for the info. By non-opposing, I meant say putting signal lights in red and blue, then it is unlike that the colorblind pilot would confuse then.

The thing is, they use three colors for light signals, so it's not just pairing.

Currently, they use white/green/red. For deuteropes, that's a problem because they wouldn't be able to distinguish green from white. For the deuteranamalous, such as myself, the green is often seen as blue so, in essence, for me the triad actually is white/blue/red - which has occasionally caused a bit of confusion when I say "see the blu--- er, green signal"

But if we went to officially red, blue and white the protanopes wouldn't be able to distinguish the red from the white. I'm not sure what a protonamalous person would see - white/yellow/blue?

Seems kinda annoying: games like Bioshock make an essential discrimination task rely on red vs. green, so truly colorblind gamers are screwed.

It IS annoying. Even as an anamalous there are a couple places in World of Warcraft I have some trouble, although WoW is implemeting a "colorblind" mode not just for red/green problems but for something like 10 different forms for colorblindness, including monochromacy. I've seen some of the testing for it and it's really helpful. That, and some of the color normals have mentioned using the modes for "mood lighting" as it were, or role playing Worgen (I guess since they're "werewolves" some folks imagine they have the color vision of dogs rather than apes). There's a bit on it here

With something like 10-11 million subscribers that works out to what, about 800,000 colorblind WoW players assuming the 8% rate applies? Yeah, probably worth the effort given that those subscriptions run to about $1,200,000 a month.

Other solutions involving labeling options for various features. But yeah, being colorblind in a gaming world can be annoying.

It's pretty common, and it would be nice if there was more interest/recognition in both simulations and aviation and driving.

I'm pretty cool with how the FAA handles the issue - it comes down to whether or not there's a safety issue. They don't care how you distinguish the colors, just that you can do so. That seems the best way to handle it as far as I'm concerned, but maybe I'm biased, being dueteranamalous

[Hari Seldon]

I wonder if I have some sort of color anomaly. What she sees as blue, I sometimes see as violet and what she sees as green, I sometimes see as blue. These are borderline distinctions, though. I have no problem with red/green though; they are entirely different.

I don't understand why the authorities permit horizontal traffic lights. They must be very difficult for red/green dichromats. My father was one and was really disconcerted by the traffic lights in Atlantic City which saved money by having only three bulbs so that the E/W traffic lights had the usual red on top, green on the bottom, while the N/S ones were reversed.

[j666]

I'm still dealing with the fact that someone tried to train cats.

[barbitu8]

Originally Posted by j666

I'm still dealing with the fact that someone tried to train cats.

Yeah. Usually it's the other way around.

[BigT]

Originally Posted by Broomstick

I really wish someone would try to come up with an alogarithim to "color correct" for us anomalous trichomats - so much emphasis seems to be on the "opes" who completly lack a particular color perception, the anomalous seem to get lost.

The emphasis is because, as you say above, you guys don't have nearly as much trouble as one would expect distinguishing colors, and thus making sure colors are distinguishable to colorblind people is usually sufficient for it to be distinguishable for anomalous trichromats. An image modifier would be more for scientific curiosity than actual practical use. Not to mention it would have to be fine tuned for each person.

Originally Posted by Hari Seldon

I wonder if I have some sort of color anomaly. What she sees as blue, I sometimes see as violet and what she sees as green, I sometimes see as blue. These are borderline distinctions, though. I have no problem with red/green though; they are entirely different.

Well, even normal trichromacy is not 100% exactly the same in every person. Both of the two color pairs you mention are often a bit off. It's not really considered anomalous, though I guess it technically is.

I don't understand why the authorities permit horizontal traffic lights. They must be very difficult for red/green dichromats. My father was one and was really disconcerted by the traffic lights in Atlantic City which saved money by having only three bulbs so that the E/W traffic lights had the usual red on top, green on the bottom, while the N/S ones were reversed.

Well, for one thing, lights in the U.S. are supposed to have a little yellow mixed into the red and blue mixed into the green. (I personally can see the latter really easily, but the former is a bit harder to see. Red-orange and red always have looked rather close to me.) But apparently the difference isn't enough for many deuteranopes, either, which sucks.

[Broomstick]

Originally Posted by BigT

The emphasis is because, as you say above, you guys don't have nearly as much trouble as one would expect distinguishing colors, and thus making sure colors are distinguishable to colorblind people is usually sufficient for it to be distinguishable for anomalous trichromats. An image modifier would be more for scientific curiosity than actual practical use.

Nothing wrong with scientific curiousity - but it WOULD demonstrate to the normal trichromats just how little problem being an anomalous is (in my opinion). It would break that idea that an anamalous trichromat somehow sees the world in monotone or is to be pitied or "fixed".

Not to mention it would have to be fine tuned for each person.

Why? Anamalous trichromats are shifted a fairly consistent amount, it's not a unique mutations for each instance.

[2gigch1]

Originally Posted by Hagen

So is there an advantage to being Colourblind?

Yes. It got me out of a LOT of grade school coloring assignments.

Interestingly I am a videographer by trade today, where color knowledge is important. I work around it.

[Ludovic]

Originally Posted by j666

I'm still dealing with the fact that someone tried to train cats.

Originally Posted by barbitu8

Yeah. Usually it's the other way around.

In Russia, Rasputin trains YOU! There is a cat that really was gone.

[Una Persson]

Originally Posted by Hagen

I was reading up the article about traffic lights and Colourblind people when I recalled a story relayed to me by a friend. Yep a bad start already, I know. It was told to him by an ex-SADF soldier during the border war who said that he had been a spotter in helicopter patrols because, being Colourblind, he could pick out camouflage from background foliage more easily.

I've heard that traffic lights' red and greens are designed to be different shades so that you can tell them apart (not that I noticed) and vaguely remember reading from an online source about a study linking colour blind animals to some selective pressure.

So is there an advantage to being Colourblind? If so it a learned skill to help one function in a three tone world,or is it intrinsic to the biology? Or is it just more lies and Internet rumours?

Kind regards
Luke

Luke

You will be pleased to know that your question was forwarded on to Cecil by myself, and he chose to run with it in today's newspaper column. You can find it here:

The Straight Dope: Is colorblindness an evolutionary advantage?

Una Persson
For The Straight Dope

[C K Dexter Haven]

Congrats, Hagen (or Luke) -- your OP has made it to Cecil's column! See: http://www.straightdope.com/columns/...nary-advantage

[TubaDiva]

Moving to "Comments on Cecil's Columns."

[thelurkinghorror]

So this is the comment thread now? A nitpick:

Cecil says: "Even today most primates are dichromats. Only a few species including humans are trichromats, with three types of cone, a trait we’re thought to have re-evolved when our ancestors took to foraging in daylight and better color vision improved their ability to find fruit." (Bolding mine)

Googling around, I figure slightly less than 100 primate species have full color vision (19 apes + ~78 OW monkeys + 1 NW monkey; and minus the few species of OW monkeys who are nocturnal and see in B&W which I don't have a count for). And that is not including the many polymorphic NW monkey females. "A few" indeed.

Also, not necessarily ignored by Cecil but not mentioned in the research he quoted: something like colorblindness can stay in the gene pool because it is not being actively selected against. So its existence does not imply that it is advantageous, just not a sufficient disadvantage. So a colorblind monkey may not be able to find ripe fruit and be at a disadvantage. Or he can just make another monkey bring him fruit. We accomplish the same thing with the grocery store, and if a pedestrian is faced with a car barreling towards him, a trichromat is unlikely to be any more likely to survive than a dichromat.

[qazwart]

Almost all amphibians, reptile, and birds have trichromatic or quad-chromatic vision.

Mammals developed during the Jurassic, Triassic and Cretaceous periods when dinosaurs ruled the earth. Mammals evolved during that period as small nocturnal creatures in order to find ecological niches that were not dominated by dinosaurs. At night long wave light vision (such as red color vision) isn't very useful, and in evolution, if you don't use a trait, you lose it. Thus, mammals lost their red color vision and became dichromatic.

It is thought that somewhere after South America and Africa split, an African species of monkey became trichromatic by duplicating the green color vision receptor onto their sex chromosome. This proved such an advantage for monkeys that this species and its offspring were able to completely replace all other African monkeys. Thus, all Old World Monkeys are trichromatic while almost all male New World Monkeys are dichromatic (it seems that many female species of New World Monkeys might be trichromatic). Apes, which evolved from Old World Monkeys are trichromatic.

That third receptor is most sensitive to yellow light, but it can be used to tell the difference between red and green and thus we have trichromatic color vision. However, due to it's sensitivity we can't see a lot of infrared colors that many other creatures have no problems with. Some animals have another receptor for ultraviolet light.

In humans, 8% of the male population are colored blind (not a good idea putting a gene for color vision on the sex chromosome), but the population of color blind monkeys and apes is much lower which seems to show that the lack of trichromatic color vision is a big disadvantage in the wild.

[typoink]

Just an anecdote: my grandfather says he was chosen as an aerial spotter for being colorblind during WWII, and claims he was able to ID a few camoflaged installations that others missed.

Also, my father's green African parrot once escaped, and my gramps was the one who spotted it in a tree.

[MEBuckner]

Originally Posted by Broomstick

There actually is a "dodecachromat", the mantis shrimp so the answer is yes to that one.

Damn those little guys are badass! If they ever get zapped by nuclear waste and grow to be more than 12 inches long*, the human race is pretty well screwed.

*Yes, I know all about the cube-square law and so forth and that the world doesn't really work that way.

[Mijin]

It's good to remind people that evolution is not necessarily about "progress". But considering the dope is supposed to be about fighting ignorance, I think a lot of people are now going to spread the "fact" that colourblindness is advantageous when really it's fairly wild speculation.

For starters, while a situation where "colourblinds" best "norms" (for the sake of brevity) is interesting, it wouldn't be hard to set up an experiment where norms beat colourblinds, so it's hardly conclusive.

Then the observations about colour vision in nature, if anything refute the hypothesis, IMO.
Most of the animals tested for colour vision, outside of mammals, are at least trichromats; if such vision were a disadvantage it's had millions of years and millions of niches to get selected out.
And if we're going to consider mammals more "advanced", then where would we fit primates and their "re-evolving" a third colour receptor?

Finally the implication that we might lose trichromacy because we don't need to select ripe fruit is dubious. Sure, we don't need to pick fruit but what we do need to do is to interact with a largely manmade world. Colour is such a useful way of showing information that much technology makes use of our full gamut of vision, and colourblinds are generally at a disadvantage wherever they are not specifically considered.
(My own view is that it's pointless extrapolating natural selection in humans; in a century or two GE and cybernetic implants may become commonplace. But that would open a big debate in itself).

[Bookkeeper]

Originally Posted by typoink

Just an anecdote: my grandfather says he was chosen as an aerial spotter for being colorblind during WWII, and claims he was able to ID a few camoflaged installations that others missed.

Also, my father's green African parrot once escaped, and my gramps was the one who spotted it in a tree.

My grandfather volunteered for the RAF in WW1 (better than being an infantry subaltern in the trenches), went through flying training, and ended up being selected as an observer rather than a pilot because he was red-green colourblind. This was in 1918, so the idea of being able to see through camouflage was an early one.

[Irishman]

Originally Posted by Lemur866

Most "colorblind" people see colors, just not in the same way as other people. So they don't see everything in greyscale.

As has been said, a normal cone cell has three kinds of color receptors. For colorblind people the red-green receptor is damaged to a greater or lesser extent. So you can distinguish shades of blue and yellow very easily, but greens and reds are hard to tell apart from browns.

Originally Posted by Broomstick

Yes. The anomalous trichromats aren't missing specific cones, it's that certain of their cones are "tuned" to slightly different frequencies. Although these people are frequently lumped in with the colorblind, they are also sometimes referred to as the "colorweak". Such a person may, for example, perceive green as a distinct color when deeply saturated but may perceive pastel or tertiary shades as something else. For example, what a person with normal color vision perceives as "yellow-green" they might see as "yellow"/

This fairly accurately describes me.

Originally Posted by Broomstick

Strictly speaking, we never "notice" the difference - what we notice is that we get into arguments with other people over the exact color/shade something is

Yep

Originally Posted by Lemur866

The only reason I would ever imagine I have some sort of color deficiency is that when they give those "what number do you see in the dots" tests, I sometimes see different numbers than I'm supposed to. But I see red, I see green, I see every color I'm supposed to see. If I look closely at the dots on the Ishihara tests I can see that there are some dots that are green rather than the background reds and pinks, but the clusters of dots don't resolve into numbers. My wife has called some shirts of mine green when I would call them brown with a touch of green. I'm semi-convinced that color-blindness is a big practical joke on gullible kids.

Most of the time it isn't an issue. However, once in Jr High science class we were doing an experiment to tell what a substance was by burning it and looking at the color, then reading a chart to ID it. Well, my lab partner and I were both colorblind, though his was worse. I did okay on most, he couldn't see most of them. But there was one that I burned and it didn't have a color at all, almost didn't seem to be burning to me. We both looked at each other, shrugged, and tried to ask the table next to us. Um, yeah.

In college I had an experiment looking at a spectrum and to me, what everyone else was calling yellow looked a bit green.

Usually it doesn't mean anything, but every once in a while I'll call something black an others will say it is green.

Looking at the images on the wiki page

The flag image, all flags look distinct, with the blue in the top flag just a big lighter than the blue in the III flag.

The protanopia image, I see the 37, though the edges aren't distinct.

The deuteranopia image I can't see the number. Even knowing it is 49, if I study hard knowing the number is 49, I can sorta see where there might be faint hints of those numbers, but it really looks like an undistinguished field that I'm projecting onto.

For the tritanopia image, the 56 is visible but faint. More of a suggestion than a distinct number.

The ishihara chart has a number that looks somewhat like it might be 81.The upright of the 4 is fairly distinct, but the inner elbow is missing.

I think, as far as camoflage goes, I agree there are probably two factors. First, the variance in color perceptions means two shades that are supposed to look different look the same, so the image isn't broken up like for normal vision. And second, colorblind people are conditioned to look for other factors to tell things apart, so edges and motion stand out more. Things like that.

[ZenBeam]

Originally Posted by Broomstick

Strictly speaking, we never "notice" the difference - what we notice is that we get into arguments with other people over the exact color/shade something is The brain isn't "compensating" at all, what is seen is what is seen, and there's never been normal color vision in that person to compare with what they see. There's no "compensating", it's that the difference is so small that it really is that meaningless outside those specific conditions you mentioned.

For those of you who are colorblind, (or perhaps only the anomalous trichromats), how do the colors on TV look? Correct? Stupid? Is it different for CRTs versus LCD or plasma? If you've seen the Quattron, with four colors of phosphors, is it better, worse, or no difference?

[thelurkinghorror]

I'm not colorblind, but those flag images always look liked poor representations of the types. Ishihara is good stuff. Irishman have you ever been diagnosed?

Colors on TV always look correct for colorblind people because that's the only percept that they know.

I wish there was info on how the Quattron worked. It would make answering that question easier.

[ZenBeam]

Originally Posted by thelurkinghorror

Colors on TV always look correct for colorblind people because that's the only percept that they know.

Not necessarily. TVs use three colors to represent what in reality is a continuum. If the balance is set for normal-sighted people, and colorblind people react to those colors differently, the colors could seem off.

(It's possible the original colors were chosen way back when to look right for colorblind people as well.)

[Irishman]

Originally Posted by ZenBeam

For those of you who are colorblind, (or perhaps only the anomalous trichromats), how do the colors on TV look? Correct? Stupid? Is it different for CRTs versus LCD or plasma? If you've seen the Quattron, with four colors of phosphors, is it better, worse, or no difference?

I've never noticed a problem with TV or movie colors. Or internet colors that nobody else complains about. Other than a few limited specific real life situations when specific shades become important, I really don't notice.

Originally Posted by thelurkinghorror

Irishman have you ever been diagnosed?

We did the standard charts in Jr High. I don't recall specifics, just being aware at that time that I could read some of the numbers.

[Broomstick]

Originally Posted by ZenBeam

For those of you who are colorblind, (or perhaps only the anomalous trichromats), how do the colors on TV look? Correct? Stupid? Is it different for CRTs versus LCD or plasma? If you've seen the Quattron, with four colors of phosphors, is it better, worse, or no difference?

The colors on the TV look just as "correct" as the colors in the real world do to this anomalous trichromat.

As it happens, we recently acquired a Quattron at my house. Yes, it does look better. Do keep in mind, though, the "fourth pixel" color is a yellow, which my eyes respond to the same as a normal trichromat would.

What I find most remarkable about the big TV we now have is not so much the color (although that is totally spectacular) but that I can actually see a difference between high definition and standard broadcasts (often I can't) and that the 3D system it has actually works with my eyesight - frequently 3D systems do work with me at all. My vision has some issues beyond just slightly off color reception, you see, but really, I'm straying off topic here.

[ollybenson]

Cecil says:

One UK study found that colorblindness was most common in the urbanized southeastern part of the country, which had been repeatedly overrun by invaders. It was much less so in the more rural north and west, where the inhabitants were more likely to have descended from Britain’s original primitive tribes.

I was trying to find the source for this research.

The closest I can is Vernon and Straker 1943, which is quoted in this paper:
http://www.ncbi.nlm.nih.gov/pmc/arti...00022-0033.pdf
(2nd page of PDF, shown as page 98)

The data and associated narrative seems to state exactly the opposite as Cecil, that colorblindness is least common in areas of the country where there had been greatest migration.

(Vernon, P. E. and Straker, A. 1943. Distribution of Colour-Blind Men in Great Britain. Nature. 152, 690 - it's available to download but for a price)