Does Light Actually Illuminate?

[SelfSim]

We generally agree on a test method for the wavelength of a red stop light. But do we agree on a test to determine whether your subjective experience of red matches a. what other people experience, and b. any objective property of the light?

The subjective differences of opinion about the 'experience' there, (which we already know happen between individuals), are sorted out by agreeing to use the word 'red', under the agreed circumstances, whenever/wherever they occur. That process is how 'something' becomes objective.

 

[durangodawood]

Not exactly; colours are mental representations of the world based on wavelengths of light; what we perceive is adjusted for colour constancy according to expectations based on past experience, so we might perceive the same wavelengths differently depending on the context. We only agree on the colour of a stoplight because the frequencies of its light are similar to the frequencies of light from other things that we call red.

There's neither wavelength nor colour in the brain, just neurons firing in patterns. It's been shown that the output of a small groups of cells in the visual cortex (the Hurvich–Jameson (H–J) opponent-process network) determines the perceived colour, and it's possible to manipulate the visual input to these cells so as to produce outputs that are outside the normal/natural range of outputs, and so enable the perception of colours that you wouldn't otherwise see (Chimerical Colors: Some Phenomenological Predictions from Cognitive Neuroscience by Paul Churchland - I have a pre-paywall copy of the PDF if you're interested).

It's only red because that's what we call the colour of things that match it visually. People with various forms of colour-blindness, and tetrachromats, will see a greater or smaller range of colours than normal, so won't always even agree on what matches and what doesn't...

Just to be sure, you havent identified anything here^ that indicates the subjective experience of red is a property of the object out there, right?

What you have identified is a representational consistency in visual processing. So red things dont sometime look green and sometimes yellow (and you eat the wrong berries and die).

 

[SelfSim]

That only works up to a point. Remember 'that dress'?

Yes .. and the we move forward with that 'imperfect' view .. but we've found that method works better than the alternative(s).

The other aspect is that we have no idea how others experience colours (or any other sensation), only that they broadly agree on names and descriptions for them.

So why is that a problem? Its obviously irrelevant as far as making practical progress. Unless one wants to go around in circles .. forever?

This is the problem of trying to compare subjective experience - it really isn't even a meaningful question to ask if my experience of red is the same as yours. It seems reasonable to assume that, having similar sensory and visual processing facilities, we have similar subjective experiences, but that's an assumption.

Where the question isn't meaningful, (as you say there), the assumption is irrelevant.

When we compare subjective experiences, it must be via intermediate steps involving metaphor and simile that appeal to other subjective experiences during common physical experiences; e.g. "I feel sick, you know, like when you go over a hump-back bridge or lean out from the top of a tall building". The other person may not find that the similes being used map to their subjective experience of feeling sick - they may enjoy the sensation of going over the bridge and may not get vertigo leaning out from a height.

And so ..(?) We all know there are differences in the way individuals experience sensations like pain. Where's the news in that?

 

[durangodawood]

The subjective differences of opinion about the 'experience' there, (which we already know happen between individuals), are sorted out by agreeing to use the word 'red', under the agreed circumstances, whenever/wherever they occur. That process is how 'something' becomes objective.

You also have only identified consistency as an objective feature of color processing. X band of visual Hz always looks the same and we call that yellow, for instance. But you havent tied the yellow as experienced to objects in any objective way. The way a color looks to me is private, right?

 

[SelfSim]

Just to be sure, you havent identified anything here^ that indicates the subjective experience of red is a property of the object out there, right?

How do you think we concluded that there was any 'object out there' in the first place? Hint: its the same method as I've outlined for you.

What you have identified is a representational consistency in visual processing. So red things dont sometime look green and sometimes yellow (and you eat the wrong berries and die).

People die from making poor assessments all the time .. its a reality y'know(?)
This so-called 'issue' of yours is like a never ending perpetual loop .. Can you see that yet?

 

[SelfSim]

You also have only identified consistency as an objective feature of color processing. X band of visual Hz always looks the same and we call that yellow, for instance. But you havent tied the yellow as experienced to objects in any objective way. The way a color looks to me is private, right?

Who said objects 'experience' anything?
'Experiences' are what a human observers undergo .. So, 'yes', you have your own private experiences, which you share when we both see a red light and call it 'red'.

 

[durangodawood]

Who said objects 'experience' anything?
'Experiences' are what a human observers undergo .. So, 'yes', you have your own private experiences, which you share when we both see a red light and call it 'red'.

When I ask about an object being "yellow as experienced [by me]" I'm asking about a putative property of the object, not an experience the object might have. I shoulda added the "by me" to make it clear.

 

[partinobodycular]

Not exactly; colours are mental representations of the world based on wavelengths of light; what we perceive is adjusted for colour constancy according to expectations based on past experience, so we might perceive the same wavelengths differently depending on the context. We only agree on the colour of a stoplight because the frequencies of its light are similar to the frequencies of light from other things that we call red.

Great post.

But it still leaves me wondering why we generally see the stoplight as red and not yellow?

One could posit that the color spectrum is a continuous transition from one end of the visual electromagnetic range to the other, and thus what we perceive as red simply conforms to its respective place on that spectrum. So the brain simply converts the incoming wavelengths to their corresponding position on the color spectrum.

But that doesn't quite fill in the whole story for me. Because this still doesn't tell me how the brain creates color. Then again, there's a lot about the brain that confuses me. This whole consciousness thing is hard.

 

[durangodawood]

...Then again, there's a lot about the brain that confuses me. This whole consciousness thing is hard.

Its a hard question.

 

[FrumiousBandersnatch]

Just to be sure, you havent identified anything here^ that indicates the subjective experience of red is a property of the object out there, right?

Right - that's what subjective means

What you have identified is a representational consistency in visual processing. So red things dont sometime look green and sometimes yellow (and you eat the wrong berries and die).

Yes, that's what colour constancy is about - although because it attempts to correct colours to make the world look sensible, it uses very simple heuristics that can easily be fooled, so that things that might look red in some contexts might not look red in other (artificial) contexts.

For example, Steven Pinker Explains Colour Constancy.

 

[SelfSim]

When I ask about an object being "yellow as experienced [by me]" I'm asking about a putative property of the object, not an experience the object might have. I shoulda added the "by me" to make it clear.

Don't you see that its you experiencing both the 'colour' and the 'object' there?
If you think there's some kind of difference there, then can you share what difference you're experiencing and we'll observe that its you who's doing the experiencing there .. regardless of whether its an object .. or a colour .. Ie: no difference at all.

 

[durangodawood]

Don't you see that its you experiencing both the 'colour' and the 'object' there?
If you think there's some kind of difference there, then can you share what difference you're experiencing and we'll observe that its you who's doing the experiencing there .. regardless of whether its an object .. or a colour .. Ie: no difference at all.

But as you noted, we have agreed on various tests for determining what to call objective. And lots of stuff out there has generally passed the test. But there seems to be no test that can tell if red the way I experience it should be called an objective property of any object.

 

[FrumiousBandersnatch]

Great post.

But it still leaves me wondering why we generally see the stoplight as red and not yellow?

Because the two sets of wavelengths generally give rise to different and characteristic patterns of neural activity - one set is associated with the word 'red' and the other with the word 'yellow'. It's reasonable to suppose that the core patterns might be broadly similar in different brains, because the brains themselves are similar, but I don't see why that's necessarily the case. All that's needed is that the patterns are different and can combine to varying degrees to produce intermediate shades, e.g. orange.

IIRC, some cultures identify additional colours in the blue-green area of the spectrum where we don't - this may be related to the language - it seems possible that learning the demarcation of the visual spectrum into named colours influences subsequent perception. Which came first is chicken & egg - I'd expect there was some utility in discriminating and explicitly naming those additional colours.

One could posit that the color spectrum is a continuous transition from one end of the visual electromagnetic range to the other, and thus what we perceive as red simply conforms to its respective place on that spectrum. So the brain simply converts the incoming wavelengths to their corresponding position on the color spectrum.

But that doesn't quite fill in the whole story for me. Because this still doesn't tell me how the brain creates color. Then again, there's a lot about the brain that confuses me. This whole consciousness thing is hard.

I'm not sure that's a coherent question - the different patterns of neural activity are there for a reason, to distinguish features of the world, so they must be experienced as something. The combinations of frequencies, intensities, etc., make up a landscape of distinguishable tones and tints, which produce appropriately related patterns of neural activity. Let's not get into textures

It seems to me that these patterns of activity are the colours we perceive. I don't see that it needs to be any more complicated or mysterious than that. The answer to why this object looks red and that object looks yellow is that light from this object results in the 'red' neural activity pattern and light from that object produces the 'yellow' neural activity pattern and those patterns may be different in your brain and my brain. The reason that pattern of activity is red or yellow, etc., is that you've learned to identify it and very similar patterns with the name 'red' or 'yellow' and with the things in the world that elicit them.

Just my take on things...

 

[Tinker Grey]

But as you noted, we have agreed on various tests for determining what to call objective. And lots of stuff out there has generally passed the test. But there seems to be no test that can tell if red the way I experience it should be called an objective property of any object.

Why would anyone say that they way you experience something is a property of an object? I'm confused.

What I believe others are saying is that some material reflects some frequency of light is a property of the object. What you are experiencing, a frequency of light, is an objective thing; the way you experience it is not.

 

[durangodawood]

Why would anyone say that they way you experience something is a property of an object? I'm confused.

What I believe others are saying is that some material reflects some frequency of light is a property of the object. What you are experiencing, a frequency of light, is an objective thing; the way you experience it is not.

Its the typical naive realist intuition to project private experiences of objects back onto the things themselves as if they are innate properties of those things.

Even after all this, I still do it myself. Its like our default mode.

 

[sjastro]

[Staff Edited Quote]
[Staff Edit]

Do we have a test to determine whether your subjective experience of red matches a. what other people experience, and b. any objective property of the light?

I offered a nuts and bolts physics explanation.
Part ‘a’ of your question is outside this scope and is in the field of psychology but I can assure you a psychologist will state the individual’s subjective experience of red reflects on the make up of the individual and not the photon.

Part ‘b’ is more relevant to physics and color is simply explained as the combination of light of different wavelengths and involves quantum mechanics where a photon is converted into a signal after which the brain or camera computer software processes the colour.
In order for this to occur there must be an objective quality to differentiate photons so an individual photon interacts with either the red, green or blue cones in your eye or is transmitted through a specific colour filter in a CCD sensor before interacting with a pixel.
Wavelength λ or the energy E where E = hc/λ is your objective quality.
Only lower energy photons which make up red light react with the red cones, higher energy photons react with the green and blue cones.
In the case of CCD coloured filters the transmission depends on the wavelength after which the signal depends on the energy of the photon.

Physicists categorize the primary colours of light according to their wavelength ranges.

 

[durangodawood]

...I offered a nuts and bolts physics explanation.
Part ‘a’ of your question is outside this scope and is in the field of psychology but I can assure you a psychologist will state the individual’s subjective experience of red reflects on the make up of the individual and not the photon.

Thats my sense too. But its a hunch. I have no way to actually know if there's some objective correspondence that would make the first person experience of color typical for all normally functioning people or not.

Part ‘b’ is more relevant to physics and color is simply explained as the combination of light of different wavelengths and involves quantum mechanics where a photon is converted into a signal after which the brain or camera computer software processes the colour.
In order for this to occur there must be an objective quality to differentiate photons so an individual photon interacts with either the red, green or blue cones in your eye or is transmitted through a specific colour filter in a CCD sensor before interacting with a pixel.
Wavelength λ or the energy E where E = hc/λ is your objective quality.
Only lower energy photons which make up red light react with the red cones, higher energy photons react with the green and blue cones.
In the case of CCD coloured filters the transmission depends on the wavelength after which the signal depends on the energy of the photon.

Physicists categorize the primary colours of light according to their wavelength ranges.

I hate to say this because you are so generous with your knowledge. But the physical processes that produce consistency of color in our mental images dont tell me that my subjective experience of "the way a color looks to me" is a definite property of the object or reflected photons that I'm seeing. If it was, then we'd have to give the opposite answer to part 'a' of the question. We'd all be experiencing the color of an object "as it really is" so long as our machinery was operating normally - which we might be....but there's no way to know.

 

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[sjastro]

Thats my sense too. But its a hunch. I have no way to actually know if there's some objective correspondence that would make the first person experience of color typical for all normally functioning people or not.


I hate to say this because you are so generous with your knowledge. But the physical processes that produce consistency of color in our mental images dont tell me that my subjective experience of "the way a color looks to me" is a definite property of the object or reflected photons that I'm seeing. If it was, then we'd have to give the opposite answer to part 'a' of the question. We'd all be experiencing the color of an object "as it really is" so long as our machinery was operating normally - which we might be....but there's no way to know.

From a physics perspective if two individuals, one with normal vision and another who is colour blind look at an apple the difference is that the colour blind individual does not have all the information, the objective property of light such as wavelength or energy to process.
For both individuals the input information is the same, the output differs due to defects in the cones of colour blind individual’s eyes.

Using Occam’s razor alone this seems to be a far more reasonable proposition than suggesting both individuals have different experiences due to some mysterious force imparted on them by the photons.
Similarly nuances between individuals with normal vision can be explained by considering the physiological and psychological aspects; the photons are not the cause.

If colour is purely a human perception then how do you explain cameras producing colour images?
The capturing of photons by pixels, the conversion of photon energies into photoelectron signals, the digitization of photoelectron signals into monochrome images and the combination of monochrome images into a final colour image is all physics and electrical engineering and involves no perception.
Ironically cameras in particular astronomical CCDs make excellent photon counters, the only thing “weird” about photons moving en masse is the photon count rate is not uniform which reveals the statistical nature of light.