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Are there any colours that our human eye cannot comprehend but other animals can see? The ability to see colours is the property of our eyes. For example an average dog would see less colours than us. So does this imply that there could be colours which the human mind cannot comprehend while some animals can see them?

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    $\begingroup$ Wouldn't this be a question more suitable for biology SE? $\endgroup$ Nov 1, 2023 at 9:23
  • $\begingroup$ The cones overlap in wavelength, so pure colors are actually activating a mixture of cones (except far red). If we could electrically stimulate only green cones we would perceive the green to end all green. We can reach into such impossible colors a little by fatiguing i.e. red and blue cones and then looking at a pure green light. On a final note, screens are horrible at making fully saturated colors. It's probably healthy to buy a physical color atlas and look though it from time to time. $\endgroup$ Nov 1, 2023 at 18:19
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    $\begingroup$ How is this a physics question? What is really the definition of "colour" here? $\endgroup$
    – ACuriousMind
    Nov 1, 2023 at 19:40
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    $\begingroup$ Ever heard of ultraviolet light? X-rays? Gamma rays? Or infrared? Microwaves? These are really wavelengths though. The actual perception of colours is completely subjective. A mix of red and blue wavelengths is just that, as is wavelengths of violet. But we perceive both as violet even though it's really not. $\endgroup$
    – DKNguyen
    Nov 1, 2023 at 20:35
  • $\begingroup$ The "false color" pictures you see as images from the Webb telescope are (in a sense) true colors, just frequency transposed by many octaves from the infrared to turn them into frequencies we can detect with our eyes. $\endgroup$ Nov 2, 2023 at 0:27

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What you call a color it's our mind perception of the effect of the electromagnetic field on our sensors related to the sense of sight - in the eyes? We should wait for a biologist - and transduced to our brain. So it really depends on the range of the sensors available.

As a result of a quick search on the web, I'll attach the reference to a study at Princeton University: to cut a long story short, hummingbirds have four different kinds of cones (4 different sensors, while human eyes has only 3) in their eyes and they can perceive the ultra-violets up-to 300nm.

enter image description here

If you're asking: what do they really perceive? Which is the color they see in the UV? Is our violet, red,... I don't know, and I guess that the researcher neither.

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    $\begingroup$ Some people have 4 different sensors, too! $\endgroup$
    – psmears
    Nov 1, 2023 at 22:21
  • $\begingroup$ LOL I didn't know it $\endgroup$
    – basics
    Nov 1, 2023 at 22:52
  • $\begingroup$ Mantis shrimp have 16(!) different types of color cones (although apparently their brains aren't advanced enough to fully utilize them) $\endgroup$ Nov 1, 2023 at 23:49
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    $\begingroup$ @psmears Simply having more cones does not imply having a greater colour detection range. I believe, at least for people, the 4th cone range is completely included in the other 3, so they do not see any "new" colour... the 4th cone simply helps discriminating some colours in the existing range. $\endgroup$
    – Bakuriu
    Nov 2, 2023 at 7:29
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    $\begingroup$ @Bakuriu That is incorrect. The fourth cone in some people helps distinguish metamers, which is literally the definition of "seeing a new color". Using an anomaloscope it is possible to determine these people, precisely because they see extra colors. $\endgroup$ Nov 2, 2023 at 10:56
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The eyes of the mantis shrimp are complicated, bizarre, and fascinating. Humans have three types of photoreceptor cells in their eyes, whereas the mantis shrimp has 12-16 different types. They can see everything from the deep ultraviolet to beyond the infrared. They even have receptors that can detect the polarization of light. Quite possibly the most impressive visual system in the animal kingdom. The term "visible light" generally refers to the light with wavelength between 400-700 nm that humans can see. The mantis shrimp's eye can detect light in the 300-720 nm range, so you could say that it can see many colors that the human eye cannot.

Vision can be a strange and fickle thing. You may find the article on Impossible Colors interesting. It discusses things like a "hyper-green" that cannot physically exist but that your eye can see if you stimulate the eye's M cones in isolation. It also talks about chimerical colors, which you can only see after staring at a strong color long enough that your receptor cells become fatigued and their color sensitivities shift. This might be the more direct answer to your question, as it shows how the notion of "color" is closely tied to the biomechanics of the eye and how even a slight, temporary change to those biomechanics can cause you to see things that can't really be described by the traditional names and notions of "color".

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The answer to this is a blindingly obvious “yes.” But my answer will provide a bit more context than that.

These alternative colors you are suggesting are simply any part of the electromagnetic spectrum that falls outside of what we typically consider visible light. Light can, of course, have essentially any wavelength or frequency related by $\lambda \nu =c$, where $\lambda$ is the wavelength, $\nu$ is the frequency, and $c$ is the speed of light in a vacuum. Human beings only typically have color receptors in their eyes allowing them to efficiently perceive light with wavelengths roughly from 380 nm (violet) to 750 nm (red). But outside of those wavelengths there are certainly still tons of meaningful types of light! Past violet going to short wavelengths you have, for example, ultraviolet radiation, X-rays, and $\gamma$ rays, which are much more highly energetic and ionizing (I.e. potentially harmful) radiation. You likely have heard about ultraviolet rays and how they are potentially damaging to our eyes if we were to look directly at the sun. On the other end going towards higher wavelengths there are, for instance, infrared, microwave, and radio wave radiations. These are not ionizing radiations typically, though infrared is infamous for its ability to heat substances by exciting the molecular vibrations. This connection between infrared light and heat is the basis of many “night-vision” technologies.

To answer your question about varieties of perception, we have examples of animals that take some advantage of radiation outside the human-visible spectrum. For instance, certain snakes can “see” infrared light. As I mentioned before, humans already have some sense of what it would be like to import further colors into our perception through “night-vision” cameras and other technologies, though these often use clever tricks to just transform these other parts of the spectrum into colors we already normally perceive. There are actually companies such as Neuralink that are working to invent or improve existing technology for neural implants to help those with disabilities to regain or obtain what we consider normal sense perception and ability. This can, however, sway into what philosophers refer to as “transhumanism,” or the effort to transcend normal human biological limitations through the use of scientific or technological intervention. In one shocking instance, an artist had a surgical implant in their skull to improve their ability to perceive colors outside the usual range! The ethics of such endeavors re still quite hotly debated and are more relevant than ever. But suffice to say there are many people working to test the boundaries of what sorts of perception enhancements may be beneficial or even possible in human beings, so someday people may be able to know what perceiving an expanded part of the electromagnetic spectrum may be like.

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    $\begingroup$ I think it's a bit more nuanced - color is usually defined as a property of visible light, not the whole EM spectrum. It kind of strains the term to suggest that X-rays or ultraviolet rays have a color. They would have a color if we could see them, but as far as humans are concerned, they are invisible and have no color. There are certainly wavelengths we can't see, but I find it odd to talk about the color of something that is downright invisible. It's like talking about the timbre of a sound that you can't hear - it's a perceptual quality that cannot exist without being perceived. $\endgroup$ Nov 1, 2023 at 19:26
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    $\begingroup$ @NuclearHoagie Further to your point, one way to think about being able to “see colors” is that it’s the ability to distinguish between light with different combinations of wavelengths. The standard-human three-cone sensor gives a wide range of these abilities, but does have different light combinations that it can’t distinguish — red+green and yellow both show up the same, as do red+blue (purple) and pure violet. Adding a fourth cone could give the ability to distinguish between these combinations, such that red+green would appear as a different color from yellow. $\endgroup$
    – RLH
    Nov 1, 2023 at 20:12
  • $\begingroup$ @RLH Even beyond that, color can be perceived differently even with identical wavelengths or sets of wavelengths. Look no further than "the dress" from 2015 as an example of people seeing the exact same image as showing completely different colors! Colors are not simply numerical wavelengths. $\endgroup$ Nov 1, 2023 at 21:00
  • $\begingroup$ This discussion is all fair, but I also think that the analogy stretches just fine. Nuances of color perception with combinations aside, I was merely addressing the perceptibility concern of the OP by pointing out that 1. Some creatures naturally have this perception, and 2. Some scientists are working to make this perception accessible to humans through artificial means. $\endgroup$ Nov 1, 2023 at 22:41
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    $\begingroup$ @MattHanson: the point that NuclearHoagie and I are elaborating on is that color is not just the 1 dimensional span of wavelengths one can detect, it’s about being able to distinguish mixes of wavelengths hitting the eye (projecting the space of possible pure or mixed wavelength lights into the ~3 dimensional space of the cones), and then being able to estimate the emmitance/absorption/reflectivity spectrum of the object based on that projection $\endgroup$
    – RLH
    Nov 2, 2023 at 1:53
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No, they do not exist because color is not an intrinsic property of a material nor a particular wavelength of radiation. Color is only human subjective experience of a particular wavelength interacting with our light receptors, and the sensation of perceiving a particular color is generated by our brain.

If you are asking whether there wavelengths outside of the visible spectrum could produce novel color sensations: probably not. There is a medical state known as aphakia which means lack of crystalline lens in the eye. Our crystalline lens filters out a part of the normally invisible UVA spectrum, and the lack of it enables people to see UVA radiation. They describe its color as whitish-violet, or in other terms a combination of previously known familiar colors. They do not report seeing a new, previously unknown color.

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    $\begingroup$ If we define color as strictly a human subjective experience, does that mean that animals by definition cannot see color at all? I think that would come as a surprise to animal researchers, and to the animals themselves :) $\endgroup$ Nov 1, 2023 at 23:11
  • $\begingroup$ Color is not just associated with wavelengths; mixes of wavelengths can have colors too. (See comments on MattHa son’s answer for a more complete description) $\endgroup$
    – RLH
    Nov 2, 2023 at 1:55
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    $\begingroup$ It is worth considering pubmed.ncbi.nlm.nih.gov/37433300 where subjects with color blindness got gene therapy for a new color receptor. They had trouble describing what they saw, but they could see it and it was different from other characteristics of light. $\endgroup$ Nov 2, 2023 at 9:44

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