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SilasBarta comments on Open Thread June 2010, Part 2 - Less Wrong

7 Post author: komponisto 07 June 2010 08:37AM

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Comment author: SilasBarta 12 June 2010 07:11:47PM *  7 points [-]

Potential top-level article, have it mostly written, let me know what you think:

Title: The hard problem of tree vibrations [tentative]

Follow-up to: this comment (Thanks Adelene Dawner!)

Related to: Disputing Definitions, Belief in the Implied Invisible

Summary: Even if you agree that trees normally make vibrations when they fall, you're still left with the problem of how you know if they make vibrations when there is no observational way to check. But this problem can be resolved by looking at the complexity of the hypothesis that no vibrations happen. Such a hypothesis is predicated on properties specific to the human mind, and therefore is extremely lengthy to specify. Lacking the type and quantity of evidence necessary to locate this hypothesis, it can be effectively ruled out.

Body: A while ago, Eliezer Yudkowsky wrote an article about the "standard" debate over a famous philosophical dilemma: "If a tree falls in a forest and no one hears it, does it make a sound?" (Call this "Question Y.") Yudkowsky wrote as if the usual interpretation was that the dilemma is in the equivocation between "sound as vibration" and "sound as auditory perception in one's mind", and that the standard (naive) debate relies on two parties assuming different definitions, leading to a pointless argument. Obviously, it makes a sound in the first sense but not the second, right?

But throughout my whole life up to that point (the question even appeared in the animated series Beetlejuice that I saw when I was little), I had assumed a different question was being asked: specifically,

If a tree falls, and no human (or human-entangled[1] sensor) is around to hear it, does it still make vibrations? On what basis do you believe this, lacking a way to directly check? (Call this "Question S".)

Now, if you're a regular on this site, you will find that question easy to answer. But before going into my exposition of the answer, I want to point out some errors that Question S does not make.

For one thing, it does not equivocate between two meanings of sound -- there, sound is taken to mean only one thing: the vibrations.

Second, it does not reduce to a simple question about anticipation of experience. In Question Y, the disputants can run through all observations they anticipate, and find them to be the same. However, if you look at the same cases in Question S, you don't resolve the debate so easily: both parties agree that by putting a tape-recorder by the tree, you will detect vibrations from the tree falling, even if people aren't around. But Question S instead specifically asks about what goes on when these kinds of sensors are not around, rendering such tests unhelpful for resolving such a disagreement.

So how do you go about resolving Question S? Yudkowsky gave a model for how to do this in Belief in the Implied Invisible, and I will do something similar here.

Complexity of the hypothesis

First, we observe that, in all cases where we can make a direct measurement, trees make vibrations when they fall. And we're tasked with finding out whether, specifically in those cases where a human (or appropriate organism with vibration sensitivity in its cognition) will never make a measurement of the vibrations, the vibrations simply don't happen. That is, when we're not looking -- and never intend to look -- trees stop the "act" and don't vibrate.

The complexity this adds to the laws of physics is astounding and may be hard to appreciate at first. This belief would require us to accept that nature has some way of knowing which things will eventually reach a cognitive system in such a way that it informs it that vibrations have happened. It must selectively modify material properties in precisely defined scenarios. It must have a precise definition of what counts as a tree.

Now, if this actually happens to be how the world works, well, then all the worse for our current models! However, each bit of complexity you add to a hypothesis reduces its probability and so must be justified by observations with a corresponding likelihood ratio -- that is, the ratio of the probability of the observation happening if this alternate hypothesis is true, compared to if it were false. By specifying the vibrations' immunity to observation, the log of this ratio is zero, meaning observations are stipulated to be uninformative, and unable to justify this additional supposition in the hypothesis.

[1] You might wonder how someone my age in '89-'91 would come up with terms like "human-entangled sensor", and you're right: I didn't use that term. Still, I considered the use of a tape recorder that someone will check to be a "someone around to hear it", for purposes of this dilemma. Least Convenient Possible World and all...

Comment author: Oscar_Cunningham 12 June 2010 07:47:17PM 2 points [-]

I think that if this post is left as it is this post would be to trivial to be a top level post. You could reframe it as a beginners' guide to Occam, or you could make it more interesting by going deeper into some of the issues (if you can think of anything more to say on the topic of differentiating between hypotheses that make the same predictions, that might be interesting, although I think you might have said all there is to say)

Comment author: AdeleneDawner 13 June 2010 05:41:53AM 3 points [-]

It could also be framed as an issue of making your beliefs pay rent, similar to the dragon in the garage example - or perhaps as an example of how reality is entangled with itself to such a degree that some questions that seem to carve reality at the joints don't really do so.

(If falling trees don't make vibrations when there's no human-entangled sensor, how do you differentiate a human-entangled sensor from a non-human-entangled sensor? If falling-tree vibrations leave subtle patterns in the surrounding leaf litter that sufficiently-sensitive human-entangled sensors can detect, does leaf litter then count as a human-entangled sensor? How about if certain plants or animals have observably evolved to handle falling-tree vibrations in a certain way, and we can detect that. Then such plants or animals (or their absence, if we're able to form a strong enough theory of evolution to notice the absence of such reactions where we would expect them) could count as human-entangled sensors well before humans even existed. In that case, is there anything that isn't a human-entangled sensor?)

Comment author: SilasBarta 13 June 2010 07:17:37PM 3 points [-]

Good points in the parenthetical -- if I make it into a top-level article, I'll be sure to include a more thorough discussion of what concept is being carved with the hypothesis that there are no tree vibrations.

Comment author: RobinZ 13 June 2010 12:11:53PM 0 points [-]

There's also the option of actually extending the post to actually address the problem it alludes to in the title, the so-called "hard problem of consciousness".

Comment author: SilasBarta 13 June 2010 07:16:18PM 2 points [-]

Eh, it was just supposed to be an allusion to that problem, with the implication that the "easy problem of tree vibrations" is the one EY attacked (Question Y in the draft). Solving the hard problem of consciousness is a bit of a tall order for this article...

Comment author: AdeleneDawner 12 June 2010 07:23:44PM 2 points [-]

I believe this is the conversation you're responding to.

(upvoted)

Comment author: SilasBarta 12 June 2010 07:31:10PM 0 points [-]

Oh, bless you[1]! That's the one! :-)

Thanks for the upvote. What I'm wondering is if it's non-obvious or helpful enough to go top-level. There's still a few paragraphs to add. I also wasn't sure if the subject matter is interesting.

[1] Blessing given in the secular sense.

Comment author: mwaser 14 June 2010 02:31:34AM -1 points [-]

And yet, the quantum mechanical world behaves exactly this way. Observations DO change exactly what happens. So, apparently at the quantum mechanical level, nature does have some way of knowing.

I'm not sure what effect that this has upon your argument, but it's something that I think that you're missing.

Comment author: SilasBarta 14 June 2010 02:43:38AM *  3 points [-]

I'm familiar with this: entanglement between the environment and the quantum system affects the outcome, but nature doesn't have a special law that distinguishes human entanglement from non-human entanglement (as far as we know, given Occam's Razor, etc.), which the alternate hypothesis would require.

The error that early quantum scientists made was in failing to recognize that it was the entanglement with their measuring devices that affected the outcome, not their immaterial "conscious knowledge". As EY wrote somewhere, they asked,

"The outcome changes when I know something about system -- what difference should that make?"

when they should have asked,

"The outcome changes when I establish more mutual information with the system -- what different should that make?"

In any case, detection of vibration does not require sensitivity to quantum-specific effects.

Comment author: JoshuaZ 14 June 2010 02:38:36AM 2 points [-]

And yet, the quantum mechanical world behaves exactly this way. Observations DO change exactly what happens. So, apparently at the quantum mechanical level, nature does have some way of knowing.

Not really. This is only the case for certain interpretations of what is going on such as in certain forms of the Copenhagen interpretation. Even then, observation in this context doesn't really mean observe in the colloquial sense but something closer to interact with another particle in a certain class of conditions. The notion that you seem to be conflating this with is the idea that consciousness causes collapse. Not many physicists take that idea at all seriously. In most version of the Many-Worlds interpretation, one doesn't need to say anything about observations triggering anything (or at least can talk about everything without talking about observations).

Disclaimer: My knowledge of QM is very poor. If someone here who knows more spots anything wrong above please correct me.

Comment author: JoshuaZ 12 June 2010 08:36:05PM 0 points [-]

This seems worthy of a top-post. When you make it a top level post link to the relevant prior posts about complexity of hypotheses.

Comment author: MugaSofer 22 January 2013 09:58:17AM -2 points [-]

But throughout my whole life up to that point (the question even appeared in the animated series Beetlejuice that I saw when I was little), I had assumed a different question was being asked: specifically,

If a tree falls, and no human (or human-entangled[1] sensor) is around to hear it, does it still make vibrations? On what basis do you believe this, lacking a way to directly check? (Call this "Question S".)

Me too! It was actually explained that way to me by my parents as a kid, in fact. I wonder if there are two subtly different versions floating around or EY just interpreted it uncharitably.