People can just about see a second octave – human visual range extends from just below 400 to just above 700 nm. If the stuff out in the tail is sufficiently bright, you can see it (I’ve seen scattered laser light from a 700 nm laser). But stuff down near 400 is going to look blue/violet, and stuff near 700 is going to look red – there’s no similarity at all. It’s not analogous to your sound example at all.
I’m sure this is due, at least in part, to the way we perceive light vs. the way we perceive sound. We sense sound using hairs in a coiled structure that gets waves set up in it – we sense sound using a mechanical mechanism that has many degrees of freedom. We sense light with cones and rods that have in one case one degree of freedom (you’re right and Exapno is wrong on this point – low-level seeing is color-blind, so our ability to perceive color isn’t an inevitable consequence of our ability to see), and in the other case three – our cones have a three-degree-of freedom ability to sense that color, which is why printing presses and colr TVs only need three inks or phosphors to reprioduce all colors. It’s as if you could duplicate all sounds using three notes. Furthermore, these sensors use photochemical sensing methods, not mechanical ones.
Isn’t it a (clearly false) implication of what you’re saying that we have evolved to know physics perfectly accurately?
Also, to gesture at some of the examples you asked for real quick between classes here:
Motion: We predict motion as though the gravity around us were earthlike. When it is not so, or when other forces take, so to speak, “precedence,” our predictions go wrong. So our predictions of motion do not fit the physics of motion, except under special circumstances. They’re the “special circumstances” we happened to evolve under, but that is beside the point. Physics did not do all the work of determining the way we expect things to move around. Selection advantages had a say as well. Evolution has not prepared us to (instinctively) grasp the truth about the physics of motion.
Color: We very often percieve color patches as similar, indeed, as the same, when they are not in fact the same or even similar. There are several fairly well known demonstrations that illustrate this fact, which I do not have cites for unfortunately. Maybe someone with a better memory than I can swoop in. And I’ve already mentioned the fact that we see colors as though it made sense to arrange them in a wheel, when in fact the physics of color do not suggest this at all.
A second question: Do you think it was possible (even if very improbable) that we might have evolved to hear fifths as “the same” rather than octaves? (Just as we have evolved, for example, to see yellow-next-to-dark-green as “the same” as grey-next-to-dark-green (or whatever) even though the physics do not directly reflect this perception?)
Finally, just for the record, it is my belief that you are the one who does not quite understand evolution. I would not normally say something like that, but as you have said it to me, I find it hard not to explain my position in return. Relevant to that is the following: I believe you and I are in roughly the same position here, as interested, fairly well read, and fairly intelligent bystanders to the actual practice of the science. If I’m wrong about that then my apologies.
You made a very specific statement: that we could have evolved in ways contrary to the laws of physics, and that indeed we had done so in several aspects.
I challenged this as impossible.
The paragraph of yours I quoted in return has no meaning at all that I can understand. I can’t even figure out what you think you’re saying to try to correct it. But your last sentence is exactly the opposite of what I’m saying: Evolution has nothing whatever to do with whether we can grasp the truth about physics; physics creates the ocean in which evolution swims.
Again, I’m not arguing that point but its opposite. Our ability to see the color blue is a consequence of blue light having a wavelength within the visible spectrum. It is not a necessary consequence, but it could only happen because it was available to us as a part of a larger set of physics.
Frylock, I think there is a disconnect because you seem to continue to insist that octaves repeat because we think they do, when, in fact, they are a natural repetition that is reflected in natural harmonics.
There could be an evolutionary advantage to us being able to identify doubling and halving of frequencies with ease, but stop insisting that octaves are a human construct. They aren’t.
And even if your sound source produces a pure sine wave, there are non-linearities in the environment and in your ears. If something is non-linear, that means the input may be a pure sine wave, but the output has flatter or pointier peaks than a pure sine wave. Such a “deformed sine wave” is actually made up of harmonics. So essentially, imperfections in the world create the harmonics. It’s not just an arbitrary thing we happen to recognize.
Actually, we hear almost pure sine waves all the time. Try whistling into a microsphone hooked up to an oscilloscope – it’s very nearly a pure sine wave. Similarly, xylophones, marimbas, glockenspiels and the like tend to produce overwhelmingly the fundamental mode (if struck in the center). the harmonics are present, inevitably, but they are of much smaller amplitude. The harmonics that also accompany this aren’t due to imperfections, but to the fact that anything but a sinusoidal driver is going to excite some proportion of higher frequencies as well. striking the bar off-center will give you odd harmonics as well as even harmonics. Even if you drive the bar using some method other than striking, most such metghods will excite other terms. It’s not imperfection, it’s just the nature of normal modes of vibration in any physical system.
Can you explain how we could evolve to hear fifths the same? How could fifths possibly cause synchronised waves within the cochlear? And if the waves aren’t synchronised then how can they possibly sound the same?
I don’t doubt that we could evolve to be able to instinctively spot the pattern of fifths just as we can see the pattern in many natural occurences. But how could we possibly be unable to differentiate them? You seem to be suggetsing that we could evolve not to be able to respond to destructive interference in wavesforms. How could such a mechanism possibly occur? And how could we continue to differentiate any tones if that were the case.
Quite simply I don’t see any plausible way in which we could evolve to hear fifths as “the same.”
I think there’s a disconnect between you and this thread. Kindly read through the thread again and take note of the several posts in it in which I say that Groman and others here have shown me how octaves are not a human construct but instead are objectively similar to each other.
It is my impression, too, Frylock, from reading this thread, that your understanding of neither physics nor evolution is a profound as you think. To be extremely elementary, but still to point out the main flaw in your evolutionary theory of octaves, evolution is entirely a negative process: it culls the weak, it does not promote the strong (except entirely by default, as they take over the resources of the culled weak). So there does not have to be a positive reason for ANY particular evolutionary trait. As long as the trait does not lessen an organism’s chance for survival, there is no evolutionary pressure to lose it. To imagine that every trait must have a positive reason for being is closer to Lamarckian theory than Darwinian, and Lamarckian verges on Intelligent Design.*
Secondly, re: your understanding of the physics of octaves. This is simply a mathematical fact, and to wonder at the evolutionary reasons for it is akin to wondering at the evolutionary reason that we are subject to gravity. It’s a nonsequitur. As I pointed out in the very first response you received in this thread, and which you dismissed sarcastically.
*A vast oversimplification, but germaine to my specific point re: negative vs. positive forces in evolutionary pressure.
“Profound as you think?” The heck’re you talking about?
You’ve misunderstood me, but understandably so. Let me clarify.
I agree, and have known all along, that not everything about an organism has always been selected for because of a reproductive (or whatever kind of) advantage. So why did I ask what reproductive advantage there is to hearing octaves as “the same?” For the following two reasons, neither of which is sufficient, but when taken together, seem to suggest there’s an evolutionary tale to be told here in terms of selection advantage:
It seemed to me that we very well could have evolved so as to hear any interval at all as “the same” rather than the octave
There is something unique and interesting about the octave interval in terms of the physics of strings and the mathematics of frequencies and so on.
This seemed to me to be an amazing coincidence–one that begs for an explanation. And when we try to explain why our organism does things the way it does, what we have available to us are evolutionary explanations. In this case the explanation “it just happened this way and there’s no pressure to lose it” doesn’t satisfy, because I’m not just asking “why are we this way” but rather “why are we this particular, amazingly coincidental way?” The “we just happen to be this way” explanation just amounts to saying “its just a huge coincidence.”
That fact 2 is the case suggests to me that there’s some reason we ended up evolving to instinctively react to octaves as “the same.” The cases in which we just sort of “happen” to do things one way and not another, with no story to be told about evolutionary advantage, are the cases in which there’s nothing particularly special about any of the possible ways of being. But there is something special about the octave: Octave note frequencies have just about the simplest relationship I can imagine frequencies having, and moreover (and related to this fact,) for example, you get an octave by dividing a string at its unique point of symmetry.
This match between our way of hearing, and certain facts about what we can do with strings and with numbers and so on, seems to indicate there’s a story to be told here. There is a good reason to think that one caused the other, or the other caused the one, or there is a single cause behind both.
Now when I posted my OP, as far as I knew, there was nothing about the physics of sound which should cause it to be that its in some way “simpler” or “easier” *physically speaking *to have a hearing anatomy which produces the feeling that octave notes sound “the same.” Groman has offered an explanation as to why I was wrong about that: It is simpler and easier and so on to hear octaves as “the same” than it would be to hear fifths as “the same.” He has explained to me how the physics of sound brings it about that this is the case. These are also the very same facts which explain the behavior of strings w.r.t. dividing them at the point of symmetry and so on. So I’ve got an explanation. My question–it was a good question–has been answered–it was a good answer.
There is a mathematical fact that the ratio of octaves (in terms of frequency) is 2 to 1.
This was all I knew (or anyway, remembered occurantly) at the time of my posting of the OP. You can see how that simple fact doesn’t tell me why it should be that octaves really are physically similar. 400 is no more similar to 200 than 250 is similar to 200.
But Groman has explained to me some other facts about the physics of sound, which help me see why it is that sounds an octave apart really are physically similar in a way that sounds a fifth apart are not.
Rather, what I was doing was akin to the following scenario. Suppose I was raised in space and never even heard of Earth. And I wonder every now and then “Now, I know things move straight forward when I throw them. But why do I keep expecting them to move downward relative to me?”
Then one day I do find Earth and land on it. After a few observations, I will have a good explanation as to why I expect things to move downward: My organism must have evolved in a place like this!
The analogy is: I was wondering, “Now, I know frequencies in sound just rise. So why do I keep hearing them going around in loops as they rise?”
Then someone explains to me some further facts about the physics of sound, and I now know: The way sound works makes it simplest and most effective to hear things the way I do in fact hear them, with octaves sounding “the same.”
I was sarcastic about your sarcastic use of “um” but other than that I think I was perfectly cordial and on point. My post was fairly detailed, and I guess maybe you didn’t read it because you were mad about my rolleyes. (Understandable.) But in that post, I tried to clarify my question in a perfectly cordial, friendly, and interesting way.
Who says we had to evolve a cochlear in order to respond differentially to sounds?
Who says that what goes on in the chochlear has to determine how we interpret sounds?
Etc.
Just because the waves are syncronized, why should they necessarily sound the same?
As Groman has explained to me, there are compelling reasons to think its best to hear them syncronized. But that doesn’t mean we actually had to hear them that way. Just that, it turns out, it was best for us if we did.
I mean, I’m just saying that it could have been that the little “layered organ” that you can find in the auditory portion of our brain (see link in my OP) could well have ended up “shifted over” in such a way that fifths, instead of octaves, appear in columns. Then we would have heard fifths as “the same” even though this doesn’t reflect the physics of sound as directly as our actual brain structures do.
There are a lot of things in our environment that are distinct that we do not distinguish between. For example, one patch on this desk has a lot of infrared emitting from it, another patch does not. But my organism does not make that distinction.
I’m not sure why we wouldn’t be able to. Can you elaborate?
In my OP, I was saying it is plausible. Since then I have changed my tune (due to Groman’s informative posts) to say its just “possible.” In other words, it really could have happened, but only very improbably.
Can you explain how we could evolve to hear fifths the same? How could fifths possibly cause synchronised waves within the cochlear? And if the waves aren’t synchronised then how can they possibly sound the same?
I don’t doubt that we could evolve to be able to instinctively spot the pattern of fifths just as we can see the pattern in many natural occurences. But how could we possibly be unable to differentiate them? You seem to be suggetsing that we could evolve not to be able to respond to destructive interference in wavesforms. How could such a mechanism possibly occur? And how could we continue to differentiate any tones if that were the case.
Quite simply I don’t see any plausible way in which we could evolve to hear fifths as “the same.”
The quote from the link explained how our perceptual structures in our eyes suggest that color can be arranged in a wheel. This is exactly what I was talking about. Our perceptual structure makes it seem like it makes sense to arrange colors into a wheel, while the physics of light do not.
I don’t believe that’s what I said, and it’s certainly not what I have ever meant.
What I have meant is that we could have (and have) evolved in ways such that our phenomenology does not match in any direct or linear fashion the physics which produces in us that phenomenology.
By a “phenomenology” here I mean just, basically, our sense perceptions and the relationships we find between them.
So, for example, it is possible (and actual) that the facts about the “color patches” that seem to us to make up our “visual percepts” do not directly reflect the facts about the frequencies of light which cause those “visual percepts.” More specifically, for example, it is possible (and actual) that we see surfaces as similar with respect to color when the frequencies of the light given off by the surfaces are actually quite dissimilar, and vice versa.
I challenged this as impossible.
People and animals in space tend still to expect objects to move downward with respect to themselves, all other things being equal. So it is possible, and actual, for us to have evolved such that our expectations as to how things should move around do not directly reflect the facts about how things actually do move around.
Also, I agree with the last sentence abovequoted. It happens that I have not intended ever to say anything contradicting it, and I don’t believe I have done so in fact, either.
The relevance of this comment is unclear to me, and I welcome you, if you think it would help, to elaborate.
So like, it would be really nice if any lurkers who actually do or are in relatively constant contact with those who do evolutionary biology or something else relevant would step in and comment on this conversation in order to aid us in our various misunderstandings.
The brain isn’t discreet, there is no matrix with frequency->octave mappings.
Neural networks (e.g. the human brain) are good at pattern recognition. They lump together similar objects and treat them as the same. This is why we can look at a jug from one angle, and recognize it as the same from another. They’re kinda similar.
As other posters have explained, notes an octave apart are mathematically similar. The must also come out in the way our brain processes sounds. So it lumps them together. We must have needed some sort of pitch distinction, and we evolved something that works well enough.
Think of other examples. Take the beat in a song. If a song doubles its beat, it sounds natural. If it switches from 4 to 7 time, it could sound strange. There’s nothing crazy going on; our brains just recognize that the doubled beat contains more elements of the first beat than a new time signature. It’s the same with frequencies, only a lot more complicated.
To be honest though, I’m not entirely sure your premise is true in all cases. I don’t think I recognized notes an octave apart as equal until somebody told me they were.
The article mentioned in the link in my OP seems to indicate otherwise. Do you think that article is probably bogus for some reason?
And that is exactly why I have been considering the question asked-and-answered since just a few posts into this thread.
This is not true. (Not as I interpret your claim.) Mathematical structures existent in the physics that works out among the things producing the stimuli do not have to be reflected in the way the brain ultimately ends up sorting out those stimuli.
I’ve shown, for example, that the way we sort colors does not reflect the mathematical similarities and dissimilarities between the frequencies of the light waves producing the stimuli in question when it comes to color.
Its a cultural universal, and lab experiments show that other mammals think of them as “the same” as well.
Can you explain how we could possibly interpret frequency without some form of resonating chamber? With no capacity to generate interference patterns or standing waves then how could an organism differentiate wavelength from simply presence of absence of a pressure wave? If you want to propose a direct stimulation model then explain how an organism can possibly differentiate between an event that generates wave peaks 400 times/sec and one that is generating 400 and 200?
We just explained this, in some depth. In a nutshell they sound the same because, being perfect multiples, they stimulate exactly the same neurons?
No, you really aren’t getting it. It’s not best that we hear them as synchronous. They really are synchronous. Saying that it’s best we here them as synchronous is like saying it’s best that we have more difficulty lifting a sheep than a cat. It’s nonsense. A sheep is actually more massive than a cat, and our muscles struggle with that extra mass. Nothing to do with what’s best. And octave notes really are synchronous and our neurons fire in synchrony. Nothing to do with what’s best.
No. I suspect you haven’t understood anything we’ve posted, or that article. The brain is arranged in octaves because it’s efficient. When a 400Hz sound and a 200 are heard simultaneously we can process thee 200 and 400 at the same time in the same location. Remember the 400 stimulates exactly the same neurons as the 200. If the brain were organized in fifths then when a 200 and 400 occurred simultaneously you would have to attempt to process the 200 signal in one location, and then process it again along with the 400 in an entirely separate location. That is hideously inefficient and would also require the signal to be replicated for splitting.
The article you linked to is not saying that we hear octaves the same because the brain is arranged in octaves as you seem to think. It is saying that when 200 and 400 sounds are detected by the 200 “column” of the brain they are processed as 200 and 400 and also get transformed into something else: a generic 200 signal by being fed across to eachother’s layer. The point I think you are missing is that by the time that conversion has occurred the brain has already recognized that the sounds are stimulating the same neurons and already processed it in the 200 part of the brain. IOW by the time they are converted into a generic octave signal they have already been processed separately.
Even if the brain were arranged into fifths as you propose, and god knows why it would or how it could, and even if the “fifths columns” converted a signal to a common fifths signal you still wouldn’t hear fifths as the same because fifths don’t stimulate the same neurons. The brain simply isn’t receiving the same input.
I think that your most fundamental problem here is that you are interpreting “pitch chroma” in the article as though it were “frequency”. That isn’t the case. If 200 and 600Hz were processed in the same location they might have a common pitch quality but they still wouldn’t sound the same unless the brain were unable to distinguish inputs from different neurons, and if that were the case we wouldn’t be able to distinguish frequency at all.
That is because you possess no neurons that are stimulated by IR. It’s that simple.
However what you propose is that you have neurons stimulated by frequency differences, and hence are able to distinguish frequency, but that they are for some reason unable to detect frequency differences caused by wavelength interaction. This is like proposing that the human eye can see IR, but it can’t see IR from reflections, only direct from the source.
How could such a mechanism possibly evolve? How could the ear distinguish between “real” frequency and frequency generated by interference? And even if it could, why would it do so?
If a 200 and 600 of the same intensity are played together the interaction will produce a wave form that is non-sinusoidal. Every second peak will be less intense than the rest… What you are proposing that somehow the body be unable to distinguish between the intensity of those peaks, and thus unable to register that interference and here 200 and 600 as the same. But if it can’t differentiate intensity of peaks then how can it here any frequencies at all? Haven’t you just produced an all-or-none system? Either the signal exists or it doesn’t?
But this puts you right back at the start. Can you explain how we could possibly evolve to hear fifths the same? How could fifths possibly cause synchronised waves within the cochlear? And if the waves aren’t synchronised then how can they possibly sound the same?
Yes, since you responded to two other posters after me I assumed you had missed my post.
Kindly read through the thread again and take note of the several posts in it in which I say that Groman and others here have shown me how octaves are not a human construct but instead are objectively similar to each other.