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

[SeventhSigma]

This thread has gone on long enough. Biology is not yet in a position to answer questions about the why or how subjective experience. We can point to areas of the brain that process colour and point to the organs responsible but we cannot really answer why blue is blue and red is red.

Thank you

As an aside, I feel like people really need to read what's being asked instead of handwaving the question away. I am really surprised at how almost everyone in this thread completely botched what I was actually arguing, here. Not saying this to be disrespectful -- but it's really frustrating to have words put in your mouth or misinterpreted/skewed/ignored.

I'm fully aware we both call blood "red." I'm fully aware the color processing is done in the brain itself and not in the receptors. I'm fully aware that we have color cones (this still ignores the fact that our brain sees colors by order of wavelength). It doesn't really matter to me if we all see the same colors for the same objects -- and it doesn't matter if my left eye sees things a bit differently than my left (personally, things have a more sepia hue to them out of my left). I think that if we *could* somehow average together the colors we see into general categories, we'd probably find that we all agree on what "red" is, "blue," interpret the same sensations for heat, cold, sourness, sweetness, etc.

But it's irrelevant to my underlying question of what, based on physical composition, brings rise to a particular set of qualia/sensations? Why does sweetness taste the way it does? Why do I perceive red as red and not blue?

 

[BruceW]

But it's irrelevant to my underlying question of what, based on physical composition, brings rise to a particular set of qualia/sensations? Why does sweetness taste the way it does? Why do I perceive red as red and not blue?

Yep, there is no answer to your question at present. As Ryan M B was saying in his last post, the 'redness' that we experience when we see a red object is not explained by any physical reason.

Similarly the experience of consciousness is a mystery. For example, we could have a world where human brains are simply a bunch of neurons and electrical signals, and the humans assert that they are conscious, but actually none of them have true consciousness or experience.
Clearly, such a world would progress in the same way as our world, so even the existence of consciousness is debatable. The reason the debate goes on is because I really do feel that I am conscious and that I see and experience the world around me.

 

[Ryan_m_b]

I forgot to mention in my last post, the answer to this question will only be found if we solve the hard problem of consciousness.

 

[sophiecentaur]

That clarification was for your benefit as you were the one who had issue with my explanation. Frankly, I think the readers would have had no problem with it.

If you read the very post that follows yours, you will see reference to RGB receptors. You will also read in a few earlier posts that "if you had only Red receptors then everything would look red". That clearly shows a huge misconception because Redness is only a quantity by which different "colours" can be recognised by using and comparing more than one analysis curve. With a single kind of receptor with a broadband response and a peak at the long wavelength end, all you would see is varying degrees of brightness. You would have no idea whether what you were looking at was producing a lot of light of short wavelength or less light of long wavelength. Moreover, you could shine 400nm wavelength light of an appropriate level and achieve a perfect 'match' to a different level of light of 600nm wavelength. They could not be distinguished. The receptors would 'see' brightness of light of all wavelengths.
With just two receptor types (short and long wavelength centred), you could probably resolve the spectral 'colours' and put them in an order of wavelength but there would be many different combinations of wavelengths ('non-spectral' colours) which would be confused much more than with our standard three sets of receptors. Moreover, even three receptors are very easily 'fooled' into seeing matches between the majority of our colour space by the appropriate mix of three primaries (Synthesis not Analysis, here). Just think how hard it would be to send colour TV pictures is this weren't the case.

Yes. Second-guessing the reader's level of understanding and nitpicking descriptions is something I don't think is bringing clarity to this thread.

I don't need to "second guess" levels of understanding when I see the same howlers about colourimetry appearing on a regular basis.

One man's "nitpicking" is another man's attention to what the other man may not appreciate as an important detail. Could it just be by chance that the CIE Colourimetric Observer functions are referred to with the letters x,y and z, rather than your favoured R, G and B? Or could it be because the CIE actually see it as an important distinction? You are justified in doubting my knowledge and expertise (and I am not at all offended and it's all good clean fun) but you could consider that the CIE may have something worthwhile to contribute to the matter.

I really believe that the reason for many of the quasi philosophical stuff that used when discussing colour is down to the fact that people don't actually understand the basic process but think they have it sussed. Interestingly, you don't come across so many similar discussions about hearing sound and music. This, I think, is because it's actually so complicated that people don't even try to over-simplify it - and, consequently, don't rush in where angels fear to tread, as they do with the colour thing.

 

[SeventhSigma]

sophiecentaur: If there has been misinformation/obfuscation in this thread, would you be so kind as to clear it up and explain things?

You seem to imply that if we only had one type of color receptor (red) we still would not see "red" at all but just light/darkness via our rods? If you were to take a human and remove all green/blue cones, they'd somehow lose red, too?

A bit confused as to what you're saying, sorry.

 

[sophiecentaur]

You only 'see red' when you can distinguish it from other 'colours'. I think you would agree with that.
So called black and white film produces an image which just varies in density. There are different types of monochrome film. Orthochrome and Panchromatic film have different sensitivity curves and give slightly different black and white prints of a particular scene because the relative sensitivities give different grey levels for different 'colours' of the same brightness. You can print onto normal b/w paper or 'tone' the paper any colour you like (e.g. sepia) but there is no colour information about the original scene.. Unlike a brain, photo paper doesn't try to second guess what it sees.


A set of cones that had only one sensitivity curve can only provide a single value of output signal which corresponds to the light level and where the wavelength of the received light happens to sit on the sensitivity curve. That, on its own, can't tell you anything about the wavelength (or combination of wavelengths) of light falling on it.

With slight differences between individuals, we mostly agree on what we call red. If we look through a 'red' filter (broad band around the long wavelength end of the spectrum) at a scene, it all looks red (named by popular consensus) but so do the green trees and the light blue sky of the original scene. But we only call it red, in fact we only have the concept of different colours, because we are aware of the different outputs of our three sensors.

Here is an analogy. If you hold your hand in front of a red hot or a white hot poker, its radiation will just give your hand the sensation of heat. There is no way you would say "that's infra red' " or "that's visible light", from the sensation in your hand. You have no mechanism for distinguishing with the heat sensors on your skin so the question of 'heat colour' doesn't arise. You couldn't describe, to someone else anything but 'a bit hot', 'very hot' or 'too hot'.

If your human subject suddenly had all but one set of sensors removed (I refuse to use the words red, green and blue in this context) then, i guess, initially, they would say that everything 'looks red'. That's because they are assuming that the other sensors are telling them that there is no spectral content at the short wavelength end. Their brain is still functioning on the assumption that it has all three sensors. Before long, as brains do, their brain would be tired of trying to differentiate between this red and that red and the other red and just treat a scene as a set of different 'grey levels'. It would lose the idea of colour because it would be irrelevant. A creature born with a single set of sensors would just not be aware of wavelength or mixtures of wavelengths so could have no concept of colour in the first place.
I have great difficulty with pictures which purport to display what other animals can 'see' in the way of colour. All we can say about the colour vision of other animals (or even other humans) is their ability to detect different em wavelengths and discriminate between the different 'colours' that we perceive and agree about. These are yet another instance of over-simplification which leads to confusion.

 

[SeventhSigma]

I'd agree that we know what red is because we can distinguish it, but there's no reason to say that if we suddenly removed the other two receptors, we suddenly wouldn't know what "red" was even though we clearly have already made the label ahead of time (via what we see). Similarly, this would be no different from someone born with only one type of receptor -- he'd still see "red" even though he wouldn't know how to differentiate it. It'd be like Terminator vision. Our brains might eventually grow tired of differentiating the red levels and might eventually push it to b/w vision, but that doesn't detract from the notion of being able to see all-red in the first place.

At the very least, the all-red example was just a way to push past the confusion that was arising as a result of talking about multicolored specta in order to just talk about one single color.

 

[bobze]

I'd agree that we know what red is because we can distinguish it, but there's no reason to say that if we suddenly removed the other two receptors, we suddenly wouldn't know what "red" was even though we clearly have already made the label ahead of time (via what we see). Similarly, this would be no different from someone born with only one type of receptor -- he'd still see "red" even though he wouldn't know how to differentiate it. It'd be like Terminator vision. Our brains might eventually grow tired of differentiating the red levels and might eventually push it to b/w vision, but that doesn't detract from the notion of being able to see all-red in the first place.

At the very least, the all-red example was just a way to push past the confusion that was arising as a result of talking about multicolored specta in order to just talk about one single color.

Sophie is onto the right thing here with sensitivity curves, I don't think they elaborated it that well though. It has to do with how ensemble coding and overlapping receptive fields (note not literally a visual field, but information field) work. I don't have time to elaborate more right now. Block exam week and I've used all my forum time :\.

I'll wax later.

 

[sophiecentaur]

I would also agree that we 'know about' red, with or without our the help of all three sensors but only because we are 'wired' to expect three inputs and have learned about it from experience. (The brain very quickly stops bothering to deal with superfluous information, however and the 'redness' of a permanently red sceenewould rapidly lose its significance, I'm sure). Give a new born baby a pair of red filtered goggles and it will develop absolutely no concept of red - or any colour value.
Many, or even all, of our subjective impressions of our world are based upon comparison and not absolute values. We can easily see which is the taller of two people when they stand next to one another. We need more extreme differences (and probably other subconscious clues and references) to do this by memory.
I still seriously believe that colour is essentially the result of three of bobze's (above) information fields. The justification is that colour reproduction, using primaries which are fed from models of our human colour sensitivity curves, works so well. Three numbers (Y,U,V: X,Y,Z : RGB: C,Y,M - take your pick) can be used to pass enough information to give a pretty good measure / match of nearly all of the visible colours (not just the spectral ones, with which so many people appear to be so totally obsessed).

I don't understand why something which can be identified in terms of three signals (to the brain, down a wire or in a computer memory) should be viewed any more philosophically than, for example, our sense of temperature. We have a very crude way of assessing the world around us in terms of the light arriving from different objects. We MAP many different combinations of spectra onto one thing that we call Colour (An amazing amount of data-compression!). That works fine, evolutionarily, and allows us to identify a useful set of information about our surroundings but it is a really poor analysis of what is actually entering our eyes. It's just (as with most of the features of our spec) good enough to get by and no better.

Will there be another thread, along the same lines, about taste and smell? Same things apply.

 

[apeiron]

I don't understand why something which can be identified in terms of three signals (to the brain, down a wire or in a computer memory) should be viewed any more philosophically than, for example, our sense of temperature...Will there be another thread, along the same lines, about taste and smell? Same things apply.

This is an interesting question. I think colour is different in that it is more "out there" and static as an experience.

So sound varies continually (though we would have a more "spectral" response to a constant tone - after a while listening to waveform, you might wonder at why a buzz is like a buzz, a rasp like a rasp).

Taste, smell and feel come through direct contact. As you say, some kinds of sensation like pressure or temperature are continuous gradients. So there is change that is quantitative but not qualitative. That seems philosophically less troubling (even if it perhaps shouldn't). But for smell and taste, as with colour, there is also quite distinct qualitative change. You have both sweet and salt - and one is not simply a greater or lesser amount of the other.

So colour has qualitative difference. It is also more out there in the world in that it seems a property of an object (rather than of wavelength information reaching our eyes). It does not change constantly, or make its appearance intermittently, or arrive as the result of some deliberate interaction, like most other sensations do.

No one is so bothered by light and dark visual experience. That is a simple continuous gradient of luminance. The object does not own the phenomenon in the same apparent way because brightness is so clearly the result of a light source.

But red seems to be something right "out there" as a definite objective qualitative property. And we expect the world to only have quantitative ones. That is, we can see the reasons why an object might have a quantity of brightness, or edge, or motion, or other such properties. The causes are also visible to us in a sense. But colour appears to be a quality of the world - lacking in the kind of cause that would make red look red, rather than some alternative hue.

So subjectively, colour is more of a mystery. We can't see its reasons as also part of the world.

Yet study the visual system and we can see that colour experience is the result of brain processes of very much the same kind as all our other experiencing. So yes, in principle, it should create no more (and no less) philosophical issues than the rest.

 

[granpa]

white-yellow
grey-green
black-blue

 

[sophiecentaur]

white-yellow
grey-green
black-blue

1. Do you mean with the same luminance?
2. Which particular sensor do you mean? Red?

But then how would you distinguish between a bright blue and a dim red? You couldn't. You would not be 'aware of colour', you would just be aware of 'brightness'.

 

[sophiecentaur]

@aperion
You have made some interesting points and I see that you, like me, have started with a belief then looked for evidence or an argument to back it up. (Ha ha - always the best way).
You, basically, are saying that colour is something a bit special. I, on the other hand, am looking for consistency. To my mind, why colour is regarded as something special is that it is a familiar quantity and, it is easy to discuss and have an opinion about. i.e. "that colour suits you" or "that shade goes with the other shade" etc. This is a bit like the way we discuss tastes and music but, in those two cases, we were never taught the equivalent to that simple ROYGBIV stuff in School as if that explains everything about colour perception. People are, in fact, much more humble about physical explanations of taste and hearing - they are more complex, I think so they don't relate the sensations to the mechanics. Someone, way back, introduced the basic idea of additive colour mixing as if it actually explains the way our eyes analyse colours. But this reverse engineering approach leads to misconceptions. It is of interest that no one ever seems to want to explain colourimetry in terms of mixing with pigments (broadband, subtractive) and relate that to our vision.

I still can't understand how people take so much for granted about the perception of 'redness' without realising that they are taking for granted that 'red' can exist in the absence of all the other colours. It's a bit like having a piano with just one key, tuned to middle C and considering playing a scale on it. If you could only hear middle C (440Hz) or, perhaps if your hearing just had one receptor with an octave bandwidth, centred about 440Hz. All frequencies within that octave would just 'sound' the same. If your sensitivity curve was a nice bell shape, extending over a few octaves and you had another hearing receptor, tuned to the C , one octave above middle C, you could tell, by looking at the relative output levels of the two sensors, what single note in that middle octave was being played. But if two appropriate frequencies were played at the same time, they could give you the 'sensation' of D,E,F ,G being played. A chord would only be interpreted as a single note. We distinguish between notes, separated by a semitone or less because we have hundreds of narrow band sound sensors - not just three, as in colour. I suppose you could say that our appreciation of musical chords of G Major, in all the possible combinations and inversions they can exist, is a bit analogous to our appreciation of a particular shade of pale yellow.
The colour of a scene has very much less important information than the spatial arrangement of the objects - so we have a very very approximate evaluation of colour. I have said it before - the eye is not a spectrometer. The Ear, on the other hand, is not only a spectrometer but it is also aware of the time variation of the spectral components of what it hears.

Yes, colour is special, in as far as it is a very crude sense and people feel familiar with it and the popular explanations about it. So much so, that we feel differently about it. I was interested that some of your comments about the specialness of colour put me in mind of the old, original 'tactile' theory of vision - where something was thought to come out of our eyes and 'feel' the presence of distant objects. There are objects for which this tactile model can for me, make sense. A pretty woman, for instance- or a cuddly puppy, to keep things healthy! Some colours, I agree, give a similar impression. But it's still just three signals which our brain associate with blurry bits of our more detailed Hi Res monochrome vision.

 

[SeventhSigma]

Yet study the visual system and we can see that colour experience is the result of brain processes of very much the same kind as all our other experiencing. So yes, in principle, it should create no more (and no less) philosophical issues than the rest.

This is true, but I think most people already understand this. It's just that since red is so "out there," it's easier to talk about. Every other aspect of sensation and consciousness/perspective is subject to the same problems.

 

[sophiecentaur]

It may be something to do with the fact that we get so much unconscious information about people's moods from colour. Its importance to us has a strong weighting in relation to its accuracy and actual information content.

 

[SeventhSigma]

I don't think it has anything to do with that, personally. I think it's because color is more "objective" for many. Most people suck at differentiating notes apart, and others might have a harder time intuiting tactile feedback, etc. Color is easy to talk about and it refer to sensations that most of us would intuitively agree upon.

 

[sophiecentaur]

You could be right. After all, you can get by in a conversation about colours using only about a dozen basic names - despite what the Dulux shade cards would imply.

 

[apeiron]

You, basically, are saying that colour is something a bit special. I, on the other hand, am looking for consistency.

Well, I thought I was agreeing that colour is not special in terms of what the brain does. So it then becomes interesting to ask why people might feel it more philosophically troubling - even if they perhaps learn the neuroscience.

And my answer is that colour experience lacks the kind of subjectively-appreciated contextual factors of other experiences.

You can in fact start to introduce a contextual view once you understand why colours can appear neon (brain making a contrast with a dark surround). Or why blackish yellow appears brown (yellow being a complementary colour synthesised at a later stage from equal red/green stimulation to create an opponent channel that gives proper context to the experience of blue).

So it is all about chipping away at the hard problem as much as possible. And this is a dual task of getting the neuroscience down pat, but also demonstrating the explanation in the kind of subjective fashion that people feel is also necessary.

Science, strictly speaking, does not demand our models of reality have this "intuitive understanding". But people still believe that is what good theory should produce for them personally. A feeling of actually knowing that is more than formal.

 

[SeventhSigma]

Color isn't any more "special" than any other aspect of perspective/consciousness, but I do think it's much easier for us to talk about. Therefore, any answer we come to about color can be more easily applied to other areas of stimuli/sensation.

I agree that it is ultimately about chipping away at the hard problem. It's definitely worth examining and not simply handwaving away because it's untestable. Consciousness is a *real* thing and part of this reality and therefore it's worth poking holes in. It may be the case that science can't ever offer a good answer, who knows.

 

[sophiecentaur]

On a nuts and bolts level, you could perhaps say that the colour experience is a bit different from many others in that it is, unashamedly, a 'many-to-one' mapping of inputs into our perception. An infinite number of spectra can all produce the same perceived colour (once you leave the boundary in colour space of the spectral colours). On the other hand, there is a good correlation between spatial distances and the perception of space by the eyes (I agree that there are many optical illusions - but they are acknowledged as such), the perception of space by touch and the perception of frequency by hearing. Smell and taste are a bit more difficult for me to place in this scheme but I don't think that smells and tastes can be reduced to a tristimulus (or any other number of stimuli) system in the same way as our colour vision. They are essentially chemical and share the field with the numerous enzymes that course around our systems - a much more ancient set of sensations.

I think colour has neatly sidestepped the rigour of treatment that other senses get and that is why people treat it as if they actually knew more than they do about the details of the process. It seems that all 'they' feel a need to discuss is the rather special cases of the spectral colours and that makes them feel they understand it all. There are certainly more acres of chat about colour than about any other of our senses.
It is a strangely demanding topic, though.

 

[Hush]

On a abstract level information theory provides the correlations needed to explain experience, perception and ultimately consciousness accessible in terms of the physical or the physics involved.

As far as information is concerned (allowed is viewing information as any infinite form of energy), the brain can be defined by the way it distributes energy introduced to it.
All forms of matter, lifeless and living, can be defined by the way the energy introduced to forms of matter are distributed.

Completely analogous to 'seeing' is 'hearing'. At the heart of both lies energy distribution.
At the core of the difference of their distribution of energy is their structure or form that determines the distribution of energy introduced.

One can continue the explanation on into physiology: a traveling wave occurs with auditory stimulation which peaks at a place corresponding to the frequency of that stimulation. The peaking of the traveling wave excites mechanically hair cell receptors. Thus, a Fourier transform is performed on the incoming signal.

In every day language the above translates or goes something like this:

You are standing next to a piano and your foot is pressing the sustain pedal. You haven't touch the keys. Instead, you clap your hands once. (You have just produced energy - in this case, called an impulse - which travels as a wave - the infamous ripple on water, but in air instead ). Eventually, this impulse reaches the undampened piano strings. All the strings will vibrate because the impulse (of energy) contains ALL the frequencies with the corresponding energies the strings need to vibrate with, at the frequencies for which the strings were built to produced. Called ground and excited state resonance. So now the clap 'sounds' quite different (like 'noise' now to you) - when the filters (strings) vibrate to transform the clap's energy the only way the strings can. That is Fourier transform.
Guess what? There is zero difference between stereocilia (ear hair cells) and piano strings!
At this point you will object. And I will be forced to agree with you. That the difference between steriocilia and piano strings is more than obvious. To my defense I will (with any scientific means available) clamor to one last straw - and always assert, so help me science, that stereocilia and piano strings perform Fourier transform. (Actually, I don't need to swear by science - because there is no scientist I can convince that something else besides a Fourier transform takes place. Luckily for me, and unluckily for you if the past and existing experiments correspond successfully to a Fourier explanation. Lucky for you if future experimentation make Fourier transform look like utter nonsense).

Going on, we now have, all neat, tidy, ORDERED and TRANSFORMED, a signal. A biochemical electrical potential (some will say compressed) all ready to go and waiting to be send as such to the brain. So how on Earth can an electrical potential, now send and stored as such (biochemically structurally imprinted) in the brain ever represent sound? Or frequency? Or loudness?

A suggestion is to explore adaptive optics. Adaptive senses, perception, adaptive neurophysiology, adaptive brain and mind. Why? When you are born on Mars and visited Earth later, not one single sense, perception, or neuronal pathway will be gear to understand what all earthlings understand under the word 'red'. Even the sound of saying the word 'red' will have a sound no earthling has ever heard.

 

[sophiecentaur]

Except that the cochlea doesn't perform a "transform" so much as a straight frequency domain 'analysis'. No sums involved. You chose to describe the incoming signal in the time domain but that's only one of two options.

 

[Hush]

The Hilbert space measure is a measure of energy distribution in the system producing a signal as well as summed information measures. The Hilbert space measure will thus distinguish between the timbre of, say, a piano and a pipe organ, as well as between a harpsichord and dulcimer, because the equations describing such systems differ in the number of degrees of freedom involved. More importantly for physiologists, such a measure will correlate with events at the basilar membrane.

The general conclusion is thus: for a system of one degree of freedom there is only one phase to the Hilbert space representation; for a system of two there are two phases; for a symmetric function y(x,y,t) = y(t,y,x) there are three, and so on. As far as information is concerned, stereocilia can be defined by the way it distributes energy introduced to it.

Generalized harmonic analysis proceeds from circular functions to Fourier analysis and then to spectral analysis. Taking into account the above considerations, a more basic sequence is to commence with energy distribution of the system, proceed to signal definition and thus to a Hilbert space representation.

Your one of two options remains open to you, regardless if this signal representation is a complete description of information or not.

 

[sophiecentaur]

You are right to say that frequency analysis, alone, is not sufficient to describe a time domain signal that does not repeat. So re-run my previous argument so that the input sensors (giving time-windowed frequency analysis) produce a large parallel set of time varying signals, which are analysed further in order to extract as much information as possible.
I should say that this is no more a "Hilbert Transform" than the process in the cochlea is a "Fourier Transform". Those two mathematical processes can only be said to give a rough equivalent result to what we 'hear' but, as I said before, there is no actual maths going on in our brains. The appreciation of sound is the result of analysis rather than transformation.
Reverse Engineering of the sensory system is risky. This same comment applies to both colour vision and hearing. Things are much more fuzzy and subjective to model closely with an Integral sign.

Normally, I would go for the Mathematical model - for electrical and mechanical situations, for instance but, even in those situations, I would not say that reality was solving quadratic equations or performing integrations.

Reverse Engineering doesn't necessarily lead to a good description of the original mechanism.

 

[John_5696]

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", well that's enough. I believe there are many logical explanation to one proposition, we use languages to represent these explanations, when it roles out we believe it is 'true'. Well I never dare to say that we actually know the 'truth', it is the same when comes to the relationship between spectrum, brain function, and human concept of color. So it is totally possible that colors can be inversed, maybe in another universe, maybe to another person, but as long as '700nm is 700nm' to me and to you, as long as logic works, it really doesn't matter whether it is 'truely' red or blue. Just let your imagination flow SeventhSigma, my friend, because that's the reason why science is fascinating!

I hope this is not much too 'philosophical'.

 

[sophiecentaur]

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.

 

[John_5696]

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.

 

[sophiecentaur]

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.

 

[fuzzyfelt]

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

 

[DaveC426913]

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.

 

[fuzzyfelt]

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.

 

[sophiecentaur]

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).

 

[DaveC426913]

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.

 

[fuzzyfelt]

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.