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The Brain is Not Computable

technologyreview.com

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Re: The Brain is Not Computable

#61

Post by seanmcdirmid »

comex wrote: post #5
seanmcdirmid wrote: post #4

Earlier quoted context omitted.

We could simulate but we'd still have problems with understanding it. Even understanding neural networks we train ourselves is very hard to impossible at our current level of enlightenment.

Maybe, but that's not the point. The article is bizarrely arguing that the brain is not computable , somehow can never be simulated with any amount of computing power, despite existing in a universe mostly described by simple mathematical laws. Ridiculous.

Ya I got that, but what would be the point of simulating if it didn't lead to understanding?

The existing universe is only mostly described by simple mathematical laws. There are still lots of gaps in our understanding, just getting all the matter position and states probably wouldn't be good enough since we don't know the exact program yet to carry the simulation forward. However, that is a technical rather than theoretical limitation.

Re: The Brain is Not Computable

#62

Post by TeMPOraL »

Such opinions happened before, and I guess will keep happening again.

> But the greater lesson lies in the vitalists' reverence for the elan vital, their eagerness to pronounce it a mystery beyond all science. Meeting the great dragon Unknown, the vitalists did not draw their swords to do battle, but bowed their necks in submission. They took pride in their ignorance, made biology into a sacred mystery, and thereby became loath to relinquish their ignorance when evidence came knocking.

> The Secret of Life was infinitely beyond the reach of science! Not just a little beyond, mind you, but infinitely beyond!

http://lesswrong.com/lw/iu/mysterious_answers_to_mysterious_...

Re: The Brain is Not Computable

#63

Post by chevreuil »

There is one constant in the History showing that a generation of human can achieve goals that were admitted impossible by their predecessor

Apart from that, there is this thing called ethnobiology, a sub-dicscipline of anthropology, that studies the way civilizations understand and represent the living things.

Ethnobiology reveals another constant in History : we tend to compare our brain to the most complex technology we know.

At the Renaissance, philosopher assimilated the brain to a very complex and subtle clockwork, Freud compared it to a steam engine, which pressure should be evacuated to avoid explosion. In the 40's, schoolboy and schoolgirls were told that brain was like a telephone exchange. Today, computers are the most advanced technology we know, so we tend to compare our brain to it. But like our predecessors, it's very likely that we are wrong.

Let just think forward, and admit that we are totally biased by the fact that computer are now inherent part of our life. Let's admit that there is a chance that our brain may never be modeled by a computer.

PS: for those who read french, a part of the above is largely inspired by a talk of Ted CHIANG, available here : http://www.actusf.com/spip/article-9802.html (sorry I can't find an English version)

Re: The Brain is Not Computable

#64

Post by jonmrodriguez »

kybernetikos wrote: post #12
guylhem wrote: post #3

Not with our current technology, I agree But saying the problem can't be solved ever seems dead wrong to me. We humans excel at understanding and replicating what nature did - then at improving it. Once we clearly understand how memories are stored, if they can be read and written that'll be half of the problem : accessing the data. If the theory about memory being encoded in the microtubules is right, imagine some n…

Computability in this case is a theoretical term and doesn't really relate to levels of technology. Whether or not all physical processes are computable in the sense that they can be simulated by a turing machine is an open question, although my impression is that most folk who care to express an opinion think that they can. There's a little bit more on the Wikipedia article on the Church-Turing-Deutsch principle. ht…

But not related to computability per se, isn't there also an issue of physical cardinality?

What I mean by this is that maybe we can't efficiently simulate a 3D human brain on any 2D computer, because there are vertical connections that are nearly instant in 3D that must map to a very very long route in a 2D "layers" simulation.

My hunch is we will efficiently simulate human brains once (1) we have finished the Human Connectome Project (2) we know much more systems biology about what happens inside both neurons and glia and (3) we have solved the heat-transfer and interconnect and yield issues in building 3D computer chips

Re: The Brain is Not Computable

#65

Post by rm999 »

amalag wrote: post #34
rm999 wrote: post #6

>But Nicolelis is in a camp that thinks that human consciousness (and if you believe in it, the soul) simply can’t be replicated in silicon. That’s because its most important features are the result of unpredictable, non-linear interactions amongst billions of cells, Nicolelis says. This is a fringe opinion, and I really wish the title reflected that. Ignoring the absurd 'linear' part of the article, I don't believe…

How are you conflating randomness with unpredictability?

I'm giving him the benefit of the doubt; unpredictable is as nonsensical as nonlinear in the context of the debate.

Re: The Brain is Not Computable

#66

Post by comex »

seanmcdirmid wrote: post #61
comex wrote: post #5

Earlier quoted context omitted.

Maybe, but that's not the point. The article is bizarrely arguing that the brain is not computable , somehow can never be simulated with any amount of computing power, despite existing in a universe mostly described by simple mathematical laws. Ridiculous.

Ya I got that, but what would be the point of simulating if it didn't lead to understanding? The existing universe is only mostly described by simple mathematical laws. There are still lots of gaps in our understanding, just getting all the matter position and states probably wouldn't be good enough since we don't know the exact program yet to carry the simulation forward. However, that is a technical rather than the…

Why simulate? For immortality and what VMs call snapshots and cloning, of course. ;p

Re: The Brain is Not Computable

#67

Post by vorg »

lutusp wrote: post #59
vorg wrote: post #56

Earlier quoted context omitted.

> the brain operates at a much higher, more macro level than quantum mechanics I didn't realize anyone had worked out the level at which quantum mechanics decoheres to Newtonian mechanics.

> I didn't realize anyone had worked out the level at which quantum mechanics decoheres to Newtonian mechanics. Well, yes, of course -- the Heisenberg Uncertainty principle is the border between them: http://en.wikipedia.org/wiki/Uncertainty_principle Equation: 𝝈x 𝝈p >= ℏ/2 I emphasize the "border" isn't a like a solid barrier, it's more a statement about probability. Also, everyone should realize that the relation…

I was thinking about Schrodinger's cat. Quantum Decoherence and Consciousness are two phenomena not yet(?) explained by science, so it's natural to wonder if they're related to each other.

Re: The Brain is Not Computable

#68

Post by lutusp »

vorg wrote: post #67
lutusp wrote: post #59

Earlier quoted context omitted.

> I didn't realize anyone had worked out the level at which quantum mechanics decoheres to Newtonian mechanics. Well, yes, of course -- the Heisenberg Uncertainty principle is the border between them: http://en.wikipedia.org/wiki/Uncertainty_principle Equation: 𝝈x 𝝈p >= ℏ/2 I emphasize the "border" isn't a like a solid barrier, it's more a statement about probability. Also, everyone should realize that the relation…

I was thinking about Schrodinger's cat. Quantum Decoherence and Consciousness are two phenomena not yet(?) explained by science, so it's natural to wonder if they're related to each other.

> Quantum Decoherence and Consciousness are two phenomena not yet(?) explained by science, so it's natural to wonder if they're related to each other.

I would credit the argument only if they had an association, not solely because they're both unexplained. Otherwise we could assume a connection between Bigfoot and the Loch Ness Monster, on the dubious ground that they're both asserted to exist but with no evidence. :)

> I was thinking about Schrodinger's cat.

It's important to say that the Schrodinger's cat experiment is a useful thought experiment, but it can't actually be carried out -- too many ways for the system to decohere.

Re: The Brain is Not Computable

#69

Post by simonster »

api wrote: post #58
bascule wrote: post #55

Earlier quoted context omitted.

This paper specifically addresses microtubules and is definitely not neglecting the interior of neurons. I suggest you read the paper instead of just the abstract before you give feedback.

Microtubules, maybe, but that's only one of a billion things going on in there. Here's a pretty decent article: http://www.nature.com/news/2011/110615/pdf/474272a.pdf My point is that a neuron is not an equation in a connection model. It's a cell. You can't hand-wave away its identity as such or all the things that happen in cells. Even if nothing quantum is involved (and I didn't say it was... we don't know), includ…

> My point is that a neuron is not an equation in a connection model. It's a cell. You can't hand-wave away its identity as such or all the things that happen in cells.

There's a huge philosophical difference between the idea that there is something going on in a brain that can't be computed (what the article suggests, and what you seem to suggest here) and the idea that a brain is hard to simulate (which is what you suggest in the next paragraph). As the posters above you have pointed out, the former is a fringe opinion unsupported by current evidence. The latter is a skeptical viewpoint to which many neuroscientists subscribe. Personally, I'm in the "I want to believe" camp.

> My intuition is that it would require a leap on the order of vacuum tube ENIAC -> Intel Core i7. Meanwhile consumer demand for faster and faster chips is giving way to demand for slower but more energy efficient chips for mobile devices, which is subtracting from the economic incentive to continue Moore's Law.

To a first approximation, speed, power consumption, and performance per dollar are all linear functions of transistor size. If you can make smaller transistors, you can make a more power-efficient chip with the same performance, or you can make a more powerful chip with the same energy consumption. I don't think people will stop innovating on this front until we hit a physical wall. There may only be one major desktop CPU maker, but there are plenty of competing fabrication plants. Since the brain is embarrassingly parallel, we only need to get within a few orders of magnitude of simulating a brain on a single chip, at which point we can just string a bunch of processors together.

> Personally I'm much more optimistic about "wet" transhumanism-- life extension, augmentation, brain hacking, etc., than I am about "real" AI in the near term or mind uploading.

If by "near term" you mean within the next 20 years or so, I agree. Beyond that, it's really hard to tell. If faster computers actually let us make scientific discoveries faster, the singularity people may well be right.

Re: The Brain is Not Computable

#70

Post by bascule »

api wrote: post #58
bascule wrote: post #55

Earlier quoted context omitted.

This paper specifically addresses microtubules and is definitely not neglecting the interior of neurons. I suggest you read the paper instead of just the abstract before you give feedback.

Microtubules, maybe, but that's only one of a billion things going on in there. Here's a pretty decent article: http://www.nature.com/news/2011/110615/pdf/474272a.pdf My point is that a neuron is not an equation in a connection model. It's a cell. You can't hand-wave away its identity as such or all the things that happen in cells. Even if nothing quantum is involved (and I didn't say it was... we don't know), includ…

A cell is a physical system. A physical system can either:

1) Be sufficiently large that quantum effects are irrelevant, like a billiard ball, and thus it can be modeled deterministically inside of a computer. The Tegmark paper proposes this is how the brain works.

2) Rely on quantum mechanical effects (which are non-deterministic, but can still be simulated inside a computer if you trust a computer's opinion of "random"). Penrose, Searle, etc. would argue otherwise, that there's a method to the madness, and that there's something "special" about the quantum mechanical effect on microtubules. We still don't understand quantum mechanics very well, so if human consciousness really relies on quantum mechanics, there is arguably a bit of wiggle room here, especially if you're a physicist of the same caliber as Penrose.

Microtubules are specifically of interest because they're one of the few brain structures small enough to arguably be subject to quantum mechanical events.

Tegmark argues that they're not small enough and that it's irrelevant.

The real question is:

Is it possible to simulate a brain within a computer?

- not -

Is it really hard? Is it too hard for modern technology? Is this problem simply too complex for us to understand? Do we lack the technology to build sufficient understanding today? Etc. Etc.

This article is claiming it's IMPOSSIBLE to simulate a brain within a computer. Proving that is a tall order.

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