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Question about the order of colors in the visible spectrum (NOT philosophy)

  1. Sep 19, 2011 #1
    Is it a silly question to ask *why* we see the orders of colors the way we do in the visible spectrum with respect to wavelength?

    For instance, I know that comparisons to dogs are often made with the following visible spectrum comparisons:

    [PLAIN]http://www.psychologytoday.com/files/u162/dog_color_vision.png [Broken]
    Notice how we still have yellows at longer wavelengths than the blues.

    Or a bee's vision (ability to see UV light):


    Or snake infrared sensors:

    At any rate, what seems important to me is that wavelengths don't have any particular color encoding in them by definition -- it's just that our brains are sensitive to a particular threshold of wavelengths and then they chop up that threshold into visible colors, ranging from red colors to violet ones (and in that order, the interesting part to me).

    My question is, though, is there any reason our brains do this? Why are the colors of the spectrum the way they are? As in, why are longer wavelengths encoded to be shifted towards red/orange/yellow colors whereas shorter wavelengths are encoded to be shifted towards green/blue/violet colors? Why couldn't the spectrum be inverted altogether?

    I am not asking that question to invite a "Well, if it were the other way around, you'd be asking the same question" response -- to me, such a response is no different from asking why the moon is round ("no matter its shape, you'd be asking that question"). I am still after the underlying explanation, which we can offer for the moon -- but can we offer it to color, as well, or is it still a huge unknown?
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Sep 19, 2011 #2


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    You should not rely on pictures "dog's vision" (snake's, bee's, etc.) Those are just silly illustrations to the fact their colour vision is different than yours. The fact that dogs (as many men...) do not distinguish between red and green, does not mean they perceive all those colours the same, as you perceive yellow.
    Actually - you can't even compare if you perceive the colours the same as your brother does. You just use the same names for colours, the names you learnt in early childhood ('green' - is a colour of 'grass'). But you can't go deeper with such comparison on perceiving colours. So - as you learnt the very basic knowledge about the world (including language and phenomenon of the rainbow) you started (after your mom) to call 'red' the colour on the outer part of the rainbow and 'blue' - the colour on inner side.
    And much later, at school, you learn, that the light you used to call 'blue' has wavelength of around 400nm, and 'red' around 700nm.

    Your metaphore with round/square Moon is not a right one. You have other definition of 'round', which actually applies to the Moon, but they might not (they actually apply only during fiuull moon). The right metaphore would be: 'why the circle is round?' or 'why all round objects are round?'

    In some languages 'moon-like' and 'round' are the same word or have the same root. For those people your metaphore would be more justified - as for them Moon defines 'roundness'...
    Last edited: Sep 19, 2011
  4. Sep 19, 2011 #3


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    I'm not sure I'm getting the gist of what you are asking, but I think you've got it backwards.

    I think the question you are (or should be) asking is:

    What is it about the long wavelength end of the spectrum that makes us see it as 'red'? What is it about the short wavelength end of the spectrum that makes us see it as 'violet'?

    I think this gets into something called 'qualia'. There is no way to define what our brains see as 'red'. There is no way to prove that what I see as red is the same as what you see as red.

    A frequency of light enters your eye, stimulates a photocell, and is sent to the brain, where it tells you 'red'.
  5. Sep 19, 2011 #4
    That is exactly what I am asking -- how do I have it backwards?

    How is it necessarily unprovable? There's good reason to believe that if all of our brains are built on the same hardware via the same evolutionary pathways, our interpretations of color should probably be pretty much the same, so I don't feel like handwaving it away with "We'll never know for sure and your red could be different from mine" is very satisfying when we're starting to understand more and more about the brain (and there's no good reason to believe we see different reds). I am just wondering if this question has made any headway in modern science.
  6. Sep 19, 2011 #5


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    Never mind, It seemed to me you though the colours were real things, and somehow our brain were picking them from reality and assigning them to frequencies.

    Colours are an entirely emergent property, occurring only in our brains.

    The fact that that is a reasonable line of logic does not make it proven. The best we can do is assume you and I both see 700nm as probably similar, but there's no way, even in principle, to know.

    Perhaps. But 'no reason' is not the same as 'reason not to'.

    For one, while our brains are generally similarly built on a gross scale, they are nowhere near close to the same. They are as unique as snowflakes, while simultaneously being billions of times more complex, and having developed dissimilarly over somewhere between 0 and 100 years (47 in my case).

    So you see it is not reasonable to assume that two brains will generally operate the same.
  7. Sep 19, 2011 #6


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    You may have only some psychological justifications (far from being precise).

    1. What is your favourite colour? (Red? no? Blue?). Launcelot and Galahad responded differently to that simple question (Galahad gave wrong answer...). It means they had different emotional associations with colours. Following your argument about "the same hardware" all people should respond the same.

    2. Different artists use different colours to express the same. Or they use the same colour to express different emotions, but also to express different impressions.

    3. In different cultures the symbolic expression of colours is pretty much different.

    4. (Especially for red) for some people red colour is irritating, for some others - it makes nice surroundings.
    Last edited: Sep 19, 2011
  8. Sep 19, 2011 #7
    You guys are taking that argument too literally/pedantically -- I don't mean to say every single brain should be exactly alike 100%. Of course we're going to have variations in the specific ways the hardware is put together (by definition, via mutation), much like a snowflake's variegated arrangements -- but they all, more or less, possess the same properties and functions.

    I'm not talking about one's opinion or reaction to a particular color -- I'm talking about the color itself as a literal property.
  9. Sep 19, 2011 #8


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    It's a bit better than that. Even if what I see as red you see as blue in a pure colour sense (if that means anything) not merely do you call it the same thing as me, but the emotional effect of it on you resembles mine so your experience is nearer mine than you might at first think. Moreover these emotional states reflect that blood is read, sky is blue, grass is green, and they are a lifetime's experience for both of us, I am getting rather convinced that red is the same for me as you. I suppose there are some interesting experiments to do by inverting people's colour perceptions, I guess we all do it by wearing tinted glasses - someone able to take this line of thought further?
  10. Sep 19, 2011 #9


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    So - literal property is that 'green' is defined as an impression caused by light of 500nm. Of course - for common use it is defined, as an colour impression you get while watching grass, leaves or Shrek, rather than 500nm waves, but those defs are -for common purposes - equivalent. There are no 'deeper' meanings of 'green' than abstraction class of 500nm and grass.
  11. Sep 19, 2011 #10
    Proof for it : http://forums.mvgroup.org/index.php?&showtopic=40553

    Create an account and download the torrent and download the video by Utorrent or bit torrent. Hope that will be enough for you to understand.
  12. Sep 19, 2011 #11


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    'More or less' leaves a pretty wide gulf of difference

    Your brain and my brain are more different than similar. We cannot assume we do things the same. In fact, we don't even process colours the same way or in the same part of the brain. It means we cannot assume that we both see red the same way.
  13. Sep 19, 2011 #12
    Based on genetics, all humans are very, very, very much similar. You're going to get obvious differences, but we're actually more the same than we are different.

    But I think it's getting needlessly silly to wonder if all humans perceive everything differently. There's more evidence to support that red is generally seen as the same red and blue is generally seen as the same blue than otherwise.

    You might say "we can't ever know for sure," but this gets into what I am asking. Clearly we have physical processes somehow giving rise to qualia. My question is how this is done.
  14. Sep 19, 2011 #13


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    Your opinion and mine on this are rhetorical, there's no accountability for what 'more similar' or 'more different' means.

    But what can be said is that you can't assume we see colours the same.

    Heck, you can't even assume you and I use the same hemisphere for processing, let alone the hundred other ways our processing might be different.

    What evidence is there? I know of none.
  15. Sep 19, 2011 #14


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    Even if we agree that "all people perceive colours the same", you still have the situation:
    - you call 370nm 'violet' (and "all people percceive it the same way")
    - you call 500nm 'green' (and all people...)
    - you call 700nm 'red'
    There is no place for any 'reverse order' nor for anything like that. We just have different wavelengths and different colours, and our eyes+brain image interpretation system maps wavelengths to colours.
    The original question is of the same kind as 'why do we feel hot water as hot and ice as cold, rather than opposite'. We just feel them differently, we have names for them, and we have our mental associations learnt in early childhood and embedded in our deepest intuitions and language.
  16. Sep 19, 2011 #15
    Right, but that is my question. What gives way to certain particular mappings between physical processes and the sensations/qualia?
  17. Sep 19, 2011 #16


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    So answer yourself (and then try to tell it to us using language...) what is a difference between that particular mapping you have and any other you could have? And how can you experimentally check if two persons have different (or identical) mappings?
  18. Sep 19, 2011 #17
    This is becoming frustrating for me because I feel like nobody is listening to my question.

    Yes, I understand that mappings "could be different," no, I don't care if different people have different mappings. But for one reason or another, we have fully physical processes (that we can describe in terms of neurons, chemicals, bio-electrical impulses, etc) giving rise to sensations.

    However, as a materialist, I have difficulty understanding how this is so -- we can discuss manifestations as existing in some real way that we can perceive even if they are themselves not physical. This is what I am asking, here. I am implicitly assuming that colors are mostly interpreted in the same way, because I think it's a reasonable assumption to make.
  19. Sep 19, 2011 #18


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    OK. So you may ssume that all people are very much similar. Let's assume for a moment that all people speak English.

    So your question is of the kind of: "why do we call the number of fingers on our hand 'five'? "
    Or - to stay in consistency with previous posts: "why do our minds map the number of fingers to word 'five', rather to any other possible word? "

    Just - there is such mapping, but every other would be equally good and it makes no much sense to think that particular one you use as better than any other possible or distinguished by any means. You may answer it using anthropic principle.

    Anyway, I advocate for noticeable differences between people: my mind maps the number of fingers to 'penki' or 'pięć' (I have a bit schisophrenic mentality), rather than to 'five'...
    Last edited: Sep 19, 2011
  20. Sep 19, 2011 #19
    I don't think that analogy is appropriate. We arbitrarily define "five" to correspond to something. We don't invent a color and associate it with something -- our brain is doing it for us. I am asking how the brain is doing that and why it decides a particular ordering of colors associated with longer/shorter wavelengths.

    If the answer is "we don't know yet," that's fine. I'm asking if modern neuroscience has made any insight here, yet.
  21. Sep 19, 2011 #20


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    There is plenty of evidence to support the reverse of that idea.

    For example different languages have widely different numbers of words for different colors, ranging from only two (black and white) or three (black, white, and red) through to hundreds. The mappings of words onto the frequency spectrum is also different. In some languages, the color of leaves is conventionally "blue", not "green", even though the language has words for both "blue" and "green". In other languages some human skin colors are described as "blue", not "black".

    If you don't have any words in your language to decribe a color like "yellow", how can anybody know that you can distinguish it from another color?

    Another example: the main reason why "indigo" was named as a distinct color in the spectrum is that Newton (who was himself partually color-blind, and had to get an assistant to help him with his experiments on the spectrum!) was convinced there ought to be seven different colors for quasi-religious reasons, despite the fact that most people can only "see" six. But if a genius like Newton said there were seven, then there are seven - end of argument!

    As earler posts have implied, there is very little that is objective about any of this.
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