Claims about private color perception

“I would say recent experiments lead us down a road to the idea that we don’t all see the same colors,” Neitz said.

Another color vision scientist, Joseph Carroll of the Medical College of Wisconsin, took it one step further: “I think we can say for certain that people don’t see the same colors,” he told Life’s Little Mysteries.

One person’s red might be another person’s blue and vice versa, the scientists said. You might really see blood as the color someone else calls blue, and the sky as someone else’s red. But our individual perceptions don’t affect the way the color of blood, or that of the sky, make us feel.

Hard for me to judge, but you can read more here, if that click through doesn’t work for you use, hat tip goes to The Browser.


"One person’s red might be another person’s blue and vice versa, the scientists said." I wonder what that can possibly mean.

There seems to be a big logical gap between "monkeys learn to perceive the red/green difference" and "color is a private sensation".

Found it:

"So the fact that we have similar emotional reactions to different lights doesn't mean our perceptions of the color of the light are the same."

Fallacy: "Not (if p then q) does not imply (if p then (not q))"

Indeed. This sounds precisely like Wittgenstein's "private language".

How so? Outsiders can test whether I can communicate to my future self via my private language, so the existence and meaningfulness of my private language is testable. Not so (as far as we can tell) for claims about color and qualia.

I wonder what that can possibly mean.

When I was a teenager I might have anwsered "what can meaning possibly mean?", and after thinking about it, I actually think that's the best answer. The question about colour has no practical importance; nor can science really answer it (though maybe it can give hints). But to get from there to "it has no meaning" requires you to have a theory of meaning - such theories a both contested and just as deamily philosophical as the original question about colours.

I think it is fair enough to be *uninterested* in these questions, but I think its better not to scorn people who are interested.

I've pondered it before. I found it didn't impress the people I want to impress.

We might be able to figure out how to test it scientifically. Speaking out of my arse here, but we can now use MRI to extract thoughts and feelings. If there are actually color centers that will be obvious. Maybe your red emotion center is connected to someone else's blue sensory center. But even if it is not that obvious, and this is where it gets science fictiony it might be possible for us to send a red from one brain's perception center to the sensory center of another brain and see what perception center it triggers.

"it might be possible for us to send a red from one brain’s perception center to the sensory center of another brain"

The idea sounds good, but as I understand it, that's just not how neural connections work. You can't send a set of signals directly into the brain to "the same place" unless the same neurons are mapped the same way in every person's brain - and they are not. The problem is that the connections are not only unique per individual, but also dynamic - how would you map them from one person to another? And if you do map them, you're just imposing the mapping as the new color - which means you can map from one color set to another, not that they are perceived differently.

On the other hand, if you want to talk about switching the data sent from the source, this might be possible. (But might not answer the question.) It may be possible to switch the cones in one person's eyes with those from another person - I don't know how this would occur, but it might be a meaningful question. At the same time, the brain would presumably need to rewire itself to account for the different input, to map the new data onto the old way of processing it. This would put us in the same place we were before - you're not comparing two people's perception.

No wonder my wife and I don't agree on what clothes match. At least now I'm not wrong.

No, you still have terrible taste.

you missed the main point that the post was trying to make.

Women are always right on these matters. Don't fight back.

If that were true, wouldn't we have much more disagreement on which colors go well together and which ones clash?

Hmm, I don't think so. A lot of color theory indicates that whether colors "do" or "don't" work together is based upon their relationship to each other on the color wheel. Just because the palette may be shifted for each person does not change the relative positions of two colors to each other.

Oh and also consider that what colors "do" and "don't" work well together are probably culturally determined to a significant extent.

That would imply, though, that if we all do have different perceptions of different colors, we are constant about the distances of those perceptions on the color wheel. That seems unlikely to me.

I looked up this wheel thing. It seems like an interesting idea, but surely someone just made the wheel up at some point? It wasn't found etched on the other side of the ten commandments?

I think someone looked at a rainbow, said "ok so far, but what about purple?" and that was that.

Two words prove this beyond all doubt: Craig Sager.

The winner going away!

That second link is gnarly dude (404)

He meant

If this is true, you'd think different people would find different colors easiest to pick out at a distance. Yet it seems to be orange for just about everyone, which is why they paint big orange blobs on the wings of planes in the arctic.

I think you are missing the difference between sensation and perception. In color vision, the former is objective and governed simply and predictably by several genes (roughly identical for all humans). The latter can, in theory, be very different between individuals - much the same way different people get perception of the various complex qualities such as taste of caviar or merits of Keynesian economics.

"taste of caviar or merits of Keynesian economics."

Ha! I'll choose caviar.

I'll take both! We need extra fiscal spending on feeding me caviar in down times. It's for the economy.

as others noted, the experiment doesn't support the strong conclusion re color relativity (in fact, it doesn't really even seem to suggest it, as reported, instead suggesting we might be able to add other colors to our palette (rather than swap them)).

Color is a social construct.

No, color is a natural element of the physical universe. Our reaction to colors can be socially influenced.

If an isolated baby was brought up by parents telling him apples and strawberries are blue he'd continue saying so. OTOH the word "Red" to ,say a Masai, has no meaning until you translate it to a color-name he has been socially conditioned to recognize.

So I'm sort of confused as to what we are really arguing here. The wavelength might be fundamental but calling it "Red" isn't.

"words are a social construct." Intelligible?

I'm color blind, so I'm fairly certain I don't see colors the same way as people with normal color vision, but it is quite a stretch to say that people with normal color vision perceive colors differently.

Color can be measured in wave lengths so that even a computer with a camera can be programed to see and respond to color in a predictable manner every time.

A human might have a range of wave lengths that create a certain cognitive or emotional reaction to "red." A different human would likely have different cognitive and emotional reactions to a wave length in that same range. Their ranges might differ slightly - a few nanometers on either end - but it's highly unlikely that a common perception of "red" is not somewhere in the intersection of their ranges.

Willitts, we're talking about the subjective perception of color. The experience of seeing color.

What on earth would it mean for your "subjective sensation" of the colour of blood to be like mine of sky blue? Despite finding the first stimulating and the second relaxing? There's no internal colour code like "255-0-0 in RGB but 0,81,73,22 in CMYK", there are just lots of neurones, wired up similarly but not identically in different people.

I think that the philosophers (and bloggers) are imagining the "real you" sitting and watching a movie inside your skull, and if the colours were (say) negative in this movie this would not change anything... but this is crazy, we know very well that this is both a natural mental image, and a very seriously misleading one.

But, fortunately, the scientists aren't so dumb. They don't say anything about this pseudo-question. The actual article is here: doi:10.1038/nature08401 .

They study a kind of monkey which naturally has only two kinds of cone cells, thus dichromatic vision. They infect some areas of the retina with a virus which replaces the gene for one of their colour sensing pigments with the gene for one of humans' three pigments. And a few weeks later these adult monkeys appear to have acquired trichromatic vision.

This means it's very likely that colour-blind humans can be given the 3rd pigment. And unlike monkeys they will be able to describe the subjective experience of seeing more colours than before.

It also seems very likely that humans can be given a 4th pigment...

On re-reading the article I see that much of what I wrote is redundant, sorry!

I am also disappointed that they did manage to get at least one of the scientists to speculate about this silly bit of grade-school philosophy...

Relevant Daniel Dennett article here:

He's lost me at: "but surely no matter how "sensitive" and "discriminating" such a system becomes, it will never have, and enjoy, what we do when we taste a wine"

Why not? How can the author justify "surely"?

He also says: "That is to say, whenever someone experiences something as being one way rather than another, this is true in virtue of some property of something happening in them at the time, but these properties are so unlike the properties traditionally imputed to consciousness that it would be grossly misleading to call any of them the long-sought qualia."

Um, but didn't he just define qualia as "the ways things seem to us"? What properties therefore don't these qualia have that they should have? His original definition was so broad that I can't see that it has any problem covering any properties. He never argues that we don't think we observe things. All his examples, like the neurosurgeon editing your brain, doesn't change that there are experiences such as "the ways things seem to us".
He makes the non-sequitor statement, that the "state of his own qualia must be as unknowable to him as the state of anyone else's qualia". But he earlier defined qualia as "the way things seem to us". How on earth can someone be experiencing things, and yet not know that they're experiencing things? If you don't know that you're experiencing things, you're not experiencing things.

The whole article seems awfully confused. Of course I can't rule out the possibility that the fault is in myself, but he does seem awfully oversure of himself, in his blithe assertion about "surely".

There is a strong temptation, I have found, to respond to my claims in this paper more or less as follows: "But after all is said and done, there is still something I know in a special way: I know how it is with me right now." But if absolutely nothing follows from this presumed knowledge--nothing, for instance, that would shed any light on the different psychological claims that might be true of Chase or Sanborn--what is the point of asserting that one has it?

I find it unbelievable that nothing follows from this presumed knowledge. Does Daniel Dennet never respond to a qualia of feeling hungry by eating something? A qualia of heat by moving his hand away from the perceived fire?
Daniel Dennet may of course be wrong in any one of these actions, eg he may be hallucinating the fire. But the idea that nothing follows from experiencing a qualia is also weird.

> He’s lost me at: “but surely no matter how “sensitive” and “discriminating” such a system becomes, it will never have, and enjoy, what we > do when we taste a wine”
> Why not? How can the author justify “surely”?

You missed the argument basically. Dennett wasn't stating his own view here, more like the opposite. Dennett first states the common view, then provides arguments to reject it.

Hmm, on re-reading I feel that there's something like an 80% probability that you're right, and I did misattribute the argument about "surely".

I still find myself deeply confused by the article. For example, at the end Dennett says: 'So when we look one last time at our original characterization of qualia, as ineffable, intrinsic, private, directly apprehensible properties of experience, we find that there is nothing to fill the bill.'
But when I look back at the start of the article, the original definition that Dennet gave says: '"Qualia" is an unfamiliar term for something that could not be more familiar to each of us: the ways things seem to us. And I still have the feeling that this article seems deeply confusing to me. My feelings about how this article seems (or a glass of milk at sunset) still strike me as neatly fitting the bill of qualia as Dennett originally defined it.
Now, I seldom see much point in arguing about words, if Dennett wants to say that the word "qualia" really means something ineffable, instrinsic, etc then as far as I'm concerned he can use "qualia" for that, and we can come up with some different word for the thing that Dennett initially introduced - the way things seem to me - perhaps "Fred". So Dennett may have found nothing to fit the characterisation of "qualia", but that still leaves me with "Fred". Dennett may have disproved "qualia", but he hasn't touched "Fred".

Or let's imagine I was convinced by Dennett's article, so Dennett's article seems convincing to me. But, if there are no qualia (or "Fred", if you prefer), how can Dennett's article be convincing to me? The more I find it convincing, the less presumably I believe that the article was convincing, because it can't have seemed like anything to me if it's right, because Dennett says that there's nothing that fits the bill of how the article seems to me.

Reminds me of that piece that claimed with certain technology, you can force the brain to perceive the normally unseeable colors blue-yellow and red-green.

Does this take us beyond Hayek & Wittgenstein & what we've already known from empirical brain science?

Not really.

I think it boils down to a statement about whether my eyes plugged into your brain would see colors differently or maybe hooking up my brain parts to your image output parts... Without some plausible connection then I think the statement is meaningless. However, I can imagine a point in time where that type of interfacing may be possible - and today's meaningless question would probably seem fairly straightforward.

I think we get fooled quite a bit still by mind-body dualism and wading around in a messy neural web where we do not have an adequate framework to pose an intelligible question. But my gut says this question is there and eventually will be answered - my guess for when is about the same time we begin to interface directly with brain signals (electrically, chemically, full-duplex style etc.).

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