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

  • #76
sophiecentaur
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Well it seems to be a very interesting topic.

To me, for example, I will first assume that the 'truth' (that red is red) is not the same as our knowledge of the 'truth' (that red is red but not blue). I'm not sure why we should differentiate red from blue, and why should I feel the same red as you are. But I'm sure that we both agree "700nm represents something red",

I hope this is not much too 'philosophical'.
I think the most you can say is that you and I would agree to call our shared experience of an object reflecting 700nm light "red". We would remember this and describe another light source which produced a similar sensation as "red". That's all.

We "differentiate" red from blue because evolution has made it a favourable characteristic. 'Colour blind' humans would have not been as successful, because there would be situations in which their failure to discriminate would affect their survival. Likewise, development of sensors with more discrimination (perhaps using four analysis curves) would have been more energetically costly for little advantage. This is 'why' tristimulus colour vision is what we have. The 'accuracy' /agreement between individuals is also something which relates to cost - benefit in the 'design'. (you know what I mean - I don't mean that old fundamentalist rubbish)
Individuals can have pretty wild differences of opinion about colour matching under some circumstances and for some colours. Mostly it doesn't matter so we aren't likely to evolve to improve it. We can discriminate much much better than we can describe. 256 levels for each channel are needed for acceptable RGB representation of colours on a display (to avoid visible contouring on large nearly-plain areas of colour), which is where the 'Millions of Colours' bit comes from. We can't actually remember more than a few dozen / hundreds of colours well enough to be able to carry a match in our heads which another person might agree with.

My view is much more pragmatic than those who say "red is red" and that there's something fundamental about it. It's all 'learned' by our brains, according to what sensors we happen to been been born with and what our peers tell us.
 
  • #77
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Thank you sophiecentaur, I totally agree with you that it is our brain which ultimately determines how we perceive and discriminate different colours and the fact that we distinguish colours better than we can describe, there is nothing fudamental about it that would make a difference. I'm not sure I get your idea of 'design', even though I can imagine some fine structure of evolution which kept fluctuating for billions of years and is different from certain church ideal that focus on a transcendental prospect. I'd love to learn more about it.

As to the 'red is red' statement, of course it is of no value to a pragmatist since it didn't reveal any detail beneath. But this is humanity, the way how certain people like me feel useful to satisfy our need for knowledge, this may also be the reason why christianity dominated the world for such a long time.
 
  • #78
sophiecentaur
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Re: "design"
The word "design" fits very nicely as a shorthand for looking at biological systems in terms of an engineering parallel - that's all. I just meant that, along with all of the rest of our 'system design', living things expend just enough energy and materials to achieve a benefit (evolutionary advantage) and no more. We have very little truly 'spare capacity' because it's a waste of energy. Along with many other characteristics, I am sure that a mutation which somehow produced colour analysis by four band analysis would die out because there is no evolutionary advantage. Our very approximate system for analysing the spectrum of light that we see is quite good enough.
My lasting objection to people's view that there is something special and absolute about 'redness' is that redness only exists as a concept because it is identifiable amongst other possible subjective values of colouredness. We place it somewhere in out perceptual colour space. Take away the options for discriminating between what we call colour and redness simply 'goes away'.

A great example of this, that I have just though of, is Monochrome TV. After a very few minutes of watching a monochrome TV programme, we completely cut out the notion of colour from what is going on on the screen. Put a red filter in front of that screen and we would still, very quickly, stop looking at the redness an just watch the film. How much more would this apply to someone whose medium and [edit] short wavelength sensors were turned off? Or if they were all re-connected in parallel to all the optic nerves which, at present, handle the signals from the long wavelength sensors.
 
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  • #79
fuzzyfelt
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once we evolved an iris we no longer needed all 3 so they evolved into color receptors.
I just wonder if this could be explained more, please? Thanks
 
  • #80
DaveC426913
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I just wonder if this could be explained more, please? Thanks
I thought he was pretty specific:
there are 3 photoreceptors

maybe one was originally for night vision and one was for day vision and one was for in-between.
He's suggesting that, once the iris came along, the eye could control how much light was let in. It could open up at night, so that the same receptors could get stimulated by less light. No longer a need for different receptors for different light levels.

Regardless, he's just tossing out a wild speculation. It's flawed - we still do have two type of receptors - rods and cones - that work better in day vs. night.
 
  • #81
fuzzyfelt
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I thought he was pretty specific:

He's suggesting that, once the iris came along, the eye could control how much light was let in. It could open up at night, so that the same receptors could get stimulated by less light. No longer a need for different receptors for different light levels.

Regardless, he's just tossing out a wild speculation. It's flawed - we still do have two type of receptors - rods and cones - that work better in day vs. night.
Thanks, I was interested in when and at what stage these differences evolved, too.
 
  • #82
sophiecentaur
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Yes. It sounded a bit speculative to me, too. Is there anything to back it up?
But the idea of a separate IR- receptive sensor (later the long, visible wavelength receptor) took my fancy. Spotting warm bodies in the dark could be definite advantage (not just at parties).
 
  • #83
DaveC426913
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Thanks, I was interested in when and at what stage these differences evolved, too.
I am pretty sure this is made from whole cloth out of granpa's head i .e. I don't think it has ever been put forth as a hypothesis - and it would be pretty easy to refute, based on the timeline of various components having evolved. But I'll leave granpa to confirm.
 
  • #84
fuzzyfelt
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Thanks both for the replies. I’m mostly just interested in more evolutionary information on receptors. I was thinking of many mammals having less differentiation in colour sensors, but understand that is due to evolutionary loss. If this is too off topic, I could start another thread.
 
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