Douglas Hofstadter - I Am a Strange Loop

Bleu Blanc Rouge = Red, White, and Blue

Let’s consider this idea. Maybe, just maybe, when all fifty million French people look at blood and declare that its color is “rouge”, they are actually experiencing an inner sensation of blueness; in other words, blood looks to them just the way melted blueberry ice cream looks to Americans. And when they gaze up at a beautiful cloudless summer sky and voice the word “bleu”, they are actually having the visual experience of melted raspberry ice cream. Sacrebleu! There is a systematic deception being pulled on them, and simultaneously a systematic linguistic coverup is going on, preventing anyone, including themselves, from ever knowing it.

We’d be convinced of this reversal if only we could get inside their skulls and experience colors in their uniquely bleu-blanc-rouge way, but alas, we’ll never do that. Nor will they ever see colors in our red-white-and-blue way. And by the way, it’s not the case that some wires have been crossed inside those French skulls — their brains look no different from ours, on every scale, from neurotransmitters to neurons to visual cortex. It’s not something fixable by rewiring, or by any other physical operation. It’s just a question of, well, ineffable feelings. And what’s worse is that although it’s true, nobody will ever know that it’s true, since nobody can ever flit from one interiority to another — we’re all trapped inside our own cranium.

Now this scenario sounds downright silly, doesn’t it? How could it ever come about that the fifty million people living inside the rather arbitrary frontiers of a certain hexagonally shaped country would all mistakenly take redness for blueness and blueness for redness (though never revealing it linguistically, since they had all been taught to call that blue sensation “red” and that red sensation “blue”)?

Even the most diehard of inverted-spectrum proponents would find this scenario preposterous. And yet it’s just the same as the standard inverted spectrum; it’s simply been promoted to the level of entire cultures, which makes it sound as it should sound — like a naïve fairy tale.

Inverting the Sonic Spectrum

Let’s explore the inverted spectrum a little further by twisting some other knobs. What if all the chirpy high notes on the piano (we do agree they are chirpy, dear reader, don’t we?) sounded very deep and low to, say, Diana Krall (though she always called them “high”), and all the deep low notes sounded chirpy and high to her (though she always called them “low”)? This, too, would be the “inverted spectrum” problem, merely involving a sonic spectrum instead of the visual one. Now this scenario strikes me as much less plausible than the original one involving colors, and I hope strikes you that way, too. But why would there be any fundamental difference between an auditory inverted spectrum and a visual one?

Well, it’s pretty clear that as musical notes sink lower and lower, the individual vibrations constituting them grow more and more perceptible. If you strike the leftmost key on a piano, you will feel very rapid pulsations at the same time as you (sort of) sense what pitch it is. Such a note is so low that we reach the boundary line between hearing it as a unitary pitch and hearing it — or rather, feeling it — as a rapid sequence of individual oscillations. The low “note” floats somewhere between singularity and plurality, somewhere between being auditory and being tactile. And if we had a piano that had fifteen or twenty extra keys further to the left (some Bösendorfers have a handful, but this piano would go quite a ways further down than they do), the superlow notes would start to feel even more like vibrations of our skin and bones rather than like pitches of sound. Two neighboring keys, when struck, wouldn’t produce distinguishable tones, but just low, gruff rumbles that felt like long, low, claps of thunder or distant explosions, or perhaps cars passing by with subwoofers blasting out their amazing primordial shaking rather than a singable sequence of pitches.

In general, low notes, as they sink ever lower, glide imperceptibly into bodily shakings as opposed to being pitches in a spectrum, whereas high notes, as they grow higher, do not do so. This establishes a simple and obvious objective difference between the two ends of the audible spectrum. For this reason, it is inconceivable that Diana Krall could have an inverted-spectrum experience — that is, could experience what you or I would call a very high sound when the lowest piano note is struck. After all, there are no objective bodily shakings produced by a high note!

Glebbing and Knurking

Well, all right. If the idea of a sonic inverted spectrum is incoherent, then why should the visual inverted spectrum seem any more plausible? The two ends of the visible range of the electromagnetic spectrum are just as physically different from each other as are the two ends of the audible sonic spectrum. One end has light of lower frequencies, which makes certain pigments absorb it, while the other end has light of higher frequencies, which makes other pigments absorb it. Unlike rumbles, though, those cell-borne pigments are just intellectual abstractions to us, and this gives some philosophers the impression that our experiences of redness and blueness are totally disconnected from physics. The feeling of a color, they have concluded, is just some kind of personal invention, and two different people could “invent” it differently and never be the wiser for it.

To spell this idea out a little more clearly, let’s posit that knurking and glebbing (two words I just concocted) are two vastly different sensations that any human brain can enjoy. All humans are created in the womb with these experiences as part of their built-in repertoire. You and I were born with knurking and glebbing as standard features, and ever since our cradle days, we’ve enjoyed these two sensations countless thousands of times. In some folks, though, it’s red light that makes them knurk and blue that makes them gleb, while in others it’s the reverse. When you were tiny, one of the colors red and blue happened to trigger knurking more often, while the other one triggered glebbing more often. By age five or so, this initial tendency had settled in for good. No science could predict which way it would go, nor tell which way it wound up — but it happened anyway. And thus you and I, dear reader, may have wound up on opposite sides of the gleb/knurk fence — but who knows? Who could ever know?

I must stress that, in the inverted-spectrum scenario, the association of red light (or blue light) with knurking is not any kind of postnatal wiring pattern that gets launched in a baby’s brain and reinforced as it grows. In fact, although I stated above that to knurk and to gleb are experiences that all babies’ brains come innately equipped with, they are not distinguishable brain processes. It’s not possible to determine, no matter how fancy are the brain-scanning gadgets that one has access to, whether my brain (or yours) is knurking or glebbing. In short, we are not talking about objectively observable or measurable facts about the brain.

If objectively observable facts were all the inverted-spectrum riddle was about, it would be as easy as pie to tell the difference between ourselves and the fifty million French people whose inner sensations are all wrong! We would just examine their gray matter and pinpoint the telltale spot where certain key connections were flipped with respect to ours. Then we could watch their French brains engage in glebbing when the identical retinal stimulus would provoke knurking in our brains. But that’s not in the least the meaning of the inverted-spectrum idea. The meaning is that, despite having identical brain wirings, two people looking at the same object experience completely different color sensations.