I believe that the visual system in human develops lot after birth in response to stimuli, so now I am wondering if that could affect color perception. If you kept an infant for six months in an environment with no red objects - no orange, no purple - would s/he be unable to process the color red, not because the cones were faulty, but because some associated brain cell was not properly wired? Would one have to also eliminate any light in the red wavelengths, if such a think could occur?
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.
A nitpick: there are actually three different kinds of cone cells, one for each of the color receptors, rather than there being three kinds of receptors in each cone.
e.g. a person who is missing either red or green cones (percept is similar enough) would see something similar to the right image here, vs. the left normal color vision.
Nitpick: There is no “red-green receptor,” as at least 2 receptor types are required to distinguish between colors like red and green. The red-green continuum appears later in the visual system than the photoreceptors. But R/G can be disrupted, by removing either cone, and then it won’t receive the necessary input to distinguish.
That should be quite easy to determine. For instance train the animal to find food in, say, a red container, then present it with two containers of different colors and see if it can pick the right one.
On a related note. Someone mentioned reptiles, etc… being quadrichromats. What color(s) can they tell apart? I mean, for instance do they see a “red1” and a “red2” where we can only see red?
Also, would it be possible (even if there is no actual example) for an animal to have more than 4 color receptors, or is it physically impossible for some reason? And if it possible, is there an upper limit, or could (in theory again) an animal be, say, dodecachromat?
Oh, and finally : is there any example of an human mutation with somehow slightly (or even radically) different cones? I’m making the assumption here that cones are “tuned” to a specific light frequency (which might be wrong) and envisioning a cone “tuned” to a somewhat lower or higher frequency than normal.
I’m not sure - color vision in animals is highly variable. Bees, for example, don’t see red but do see ultraviolet. Other animals, such as reptiles and birds, may have more photoreceptors for the human visiual spectrum.
There actually is a “dodecachromat”, the mantis shrimp so the answer is yes to that one. So far as I know, that’s currently the upper limit but whether that’s an absolute or simply no other critter has had reason to evolve more I don’t know.
Among other critters, there is apparently some evidence that some birds, such as pigeons, are pentachromats.
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”/
It’s really impossible to understand how colors we can’t perceive might look to an animal which can see them. How would you describe the sensation of “red” to a color-blind person?
Many tetrachromats such as birds can perceive into the ultraviolet. (In fact, it has been determined that some birds that look drab to us are brightly “colored” in the ultraviolet.) What ultraviolet might look like as a color is as unimaginable to us as red would be to a dog.
Have a link? Sometimes LASIK leaves people with 20/10, but it doesn’t affect the retina. The upper theoretical limit of your acuity is limited by the width of one cone (rods are wider), but they are already packed in there, I don’t know if the amount of new cones you can add would be enough to make a difference?
Colibri covered it, but for example see spectral sensitivity curves. A new cone would work best if it is in a area of “low coverage,” e.g. ultraviolet to the left, between S/M in middle, or infrared to the right. Most suspected human tetrachromats would have a fourth cone close to the L, M, so no mindblowing changes.
Fun fact, Colibri’s namesake, the hummingbirds, (or at least among the whole Trochilidae family) sometimes have two foveae, or areas of the retina with high acuity and lots of cones and color vision.
There are also some flowers that look identically dull to humans but look vividly different to a bee, sometimes looking like a “bullseye.”
Also, the differences in an anomalous trichromat is small enough that the brain can compensate for the shift, which cannot be done if the cone is completely missing. So anomalous people may only rarely notice a difference or defect in extremely limited conditions.
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.
And, given how little being an anomalous trichromat actually affects one’s ability to function, and that most of the disability is due to societal rules (those “extremely limited conditions” you mentioned), I’m sure if “defect” is really the best word to describe it. I mean, being left-handed is statistically rare and sometimes awkward, but for the most part we’ve dropped calling it an outright defect.
If you determine what a anomalous trichromat’s actual peak sensitivities are, and use them to determine what a picture would look like to this individual solely based upon the cones, then you would see an extremely impoverished color experience. However, the brain can adapt by adjusting color weightings, or ratios, etc. post-receptorally, thus these individuals see almost normal. So no it’s not really a defect, although the one or two anomalous trichromats I have spoken to say they “believe” they don’t have normal color vision, but can’t say how. I doubt the difference is large enough to say, pose a evolutionary disadvantage, and mainly shows up in things like pigments and computer displays.
After looking at a number of color-shifted pictures I’ve reached the conclusion that my particular brand of “red-green” colorblindness is a decreased sensitivity to red. I still see red but it’s obviously more vibrant to chromo-typicals. As others have mentioned my difficulties are all from color disagreements with CTs or with color schemes that were designed or chosen by CTs.
However I remember reading some speculation that color blind men fared poorly during the Irish potato famine – I suppose because they couldn’t distinguish good from infected plants. Thus Irish immigrants to America were disproportionately colorblind. I don’t know if there is any substance to either of those claims.
Well, no, actually I wouldn’t, as I’m an anomalous trichomat myself and thus that IS my normal. I suspect that if someone bothered to color-adjust something so that my eyes would see it as a normal trichromat would I’d think the result to be garrish, over-saturated, perhaps cartoonish or something.
But if you’re going that route, you might as well say that all photographs should be viewed upside-down as that is how the images are actually projected onto the retina. Vision isn’t just what’s going on in the eyes, it involves lots of neural processing.
For that matter, people with normal color vision perceive colors as constant even under wildly different levels of light. If you were to project a picture of, say, a backyard on an overcast day based solely on what the cells of the eyes perceive and set it next to that of a bright, sunny day at noon the overcast day would also be extremely impoverished color-wise, yet for the most part people just don’t notice it. Their brains “color-correct” to a very large degree, so really what you’re talking about is something both normal trichromats and anomalous trichromats share.
I was well into my 30’s before I was informed I was an anomalous trichromat, despite pursuing a career in the arts which included as some points color illustrations. It is entirely possible for an anomalous trichromat to live his or her entire life without ever realizing he or she has the condition. That’s a damn small difference.
About the only place it shows up in my life is that I have a coat which, in most light, I perceive as a greenish brown and normal trichromats perceive as a brownish green.
I actually have a very good idea at this point how and when there is a difference between my color perception and the norm, but then, I do have a degree in art and for a layperson I’m literate in science in medicine.
More computer displays than pigments, in my experience. For awhile, when green and greenish colors seemed to become trendy for a bit I encountered a few problematic websites.
When it comes to painting and illustration, which I have done both in the sense of painting buildings and in making images, there are practices that virtually eliminate problems. For example, when painting a house for a customer I let the customer choose anyway (though I might offer some very tentative advice or opinion if asked) and then get all the paint mixed at one time, for a completely consistent color. In many instances when doing illustrative or dye work you’re using either very specific colors such as the Pantone group or precise formulas to give consistent results.
Where my anomalous trichromacy was discovered was when I went for my first FAA physical to get my pilot’s license. At the time they were using the Ishihara test, which is way more sensitive than piloting really requires (I’ve applied for other jobs that involved testing color perception with different testing methods where I tested out completely normal thus demonstrating once again that anomalous trichromacy is often an irrelevant difference. A lot of color-testing won’t catch it.) I easily passed the light-gun demonstration of ability test. Even though there was a detectable difference I still have no difficulty in the real world distinguishing colors in aviation sufficiently to avoid safety hazards, which is the real concern there. That is probably why the FAA is no longer requiring a SODA but using wavier letters for those of us with slightly off the norm color perception.
With humans, we can do non-invasive testing and based on their answers make a determination.
But with individual cells I suppose there’s some very fancy way of determining what makes it react. Maybe analyzing light-sensitive pigments, or seeing when a nerve fires in response to a stimulus.
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.
This has proven to be problematic with some animals. If you look at the cells of their eyes, cats and dogs should both be partially colorblind. With dogs, this is actually fairly easy to prove using food and colored bowls or containers, exactly as you suggested. You can tell pretty accurately what colors a dog can and can’t see.
Cats, however, despite having some color receptors in their eyes, won’t choose food based on container color. For a very long time, researchers thought that cats were somehow deficient elsewhere, perhaps lacking something in their brain to process the color information from their eyes. It wasn’t until the 60s or 70s that someone was able to prove that cats are not in fact colorblind, and can be trained to select food based on container color. For some reason, though, training cats to do this is extremely difficult. And by extremely difficult we’re talking well over a thousand tries before they finally start to get it right. No wonder researchers used to believe they were colorblind. After trying it a few hundred times with complete failure you’d be tempted to write cats off as colorblind as well.
And after googling to make sure I had the order of magnitude of the cat trials right, it turns out I learned this originally from Uncle Cecil. Here’s his article on it:
If I can wildly speculate on the topic question a bit…
Aside from the already great answers given about how colorblind people see camouflage differently, I would venture that full-colored brains are “wasting” energy on color that colorblind brains may devote to edge and motion recognition. When analyzing pictures, a common thing to do is use filters that effectively reduce the amount of information your brain is receiving at one time. Being colorblind could reduce the overall complexity of the scene, making it easier to spot an anomaly like movement.
The brain is a plastic thing and developing with color-compromised vision would most likely result in a focus on things the eyes can see. It wouldn’t be “super-vision” or anything like that, but it might give you an edge.
Of course, colorblindness also leaves you vulnerable to all the troubles listed above and more, which is why you would not want to rely exclusively on people with it.
Some are born with better than 20/20. I knew someone who had 20/10. Many pilots have better than 20/20. I was told by an optometrist that the difference is in the number of cones. If this is not so, how do you explain vision better than 20/20?
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.
