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The Brain is Not Computable

39 points by petermlm 14y ago

coopdog 14y ago
Surely if you created a physics virtual machine and loaded an image with all of the atoms and electrons in place.. you'd simulate the brain. I imagine it would take a lot of computational power, but it's not 'never' Unless we're talking about souls here or something
- seanmcdirmid 14y ago
  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.
  - comex 14y ago
    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.
    - seanmcdirmid 14y ago
      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.
      - comex 14y ago
        Why simulate? For immortality and what VMs call snapshots and cloning, of course. ;p
- stefantalpalaru 14y ago
  If we really need to simulate interactions at molecular level we're fracked. That kind of computational power is unimaginable.
  - kristofferR 14y ago
    So was Petabytes 60 years ago, yet today there are people who have single-handedly uploaded more than that on private BitTorrent trackers. Never say never.
guylhem 14y ago
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 nanomachines that could read it from a "live" human - by broadcasting radio waves, or emitting photons (we started doing that for proteins with antibodies glued to radioactive markets, then we improved and glued them luciferase, now we do multiple colors and IIRC it's being experimented for DNA), whatever. Now imagine other nanomachines that could rearrange the microtubules to match that - voila, you've got Matrix-style "uploading" of knowledge once we understand how the memory bits interact with eachother, how they can be accessed by the subject. Maybe it's like a SQL database fk/pk - we don't know. But something must exist to allow it. When we figure it out, there is no reason why it couldn't be done too. My own predictions : after we confirm how memories are stored, if we have nanotechnologies to create nanomachines, we will start reading memories just like we did with DNA and proteins. It will take a while, we will only have a read-only access at first- and with many bugs just like how introns and TATA boxes could be mysterious initially - but we will understand in the end, and that will be half of the problem solved. Downloading will require additional advances in computer technology (at least faster cpus, in 3d instead of 2d to get more interconnections and raw computing power, and maybe some integration of processing and memory to match how neurons work), but it does not seem far-fetched to me.
- kybernetikos 14y ago
  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. http://en.wikipedia.org/wiki/Church%E2%80%93Turing%E2%80%93Deutsch_principle http://en.wikipedia.org/wiki/Church%E2%80%93Turing%E2%80%93D...
  - 14y ago
rm999 14y ago
>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 predictability is important to the brain. While it's possible quantum effects could explain unpredictability in the physical universe, there is no scientific evidence this is relevant to the brain; the brain operates at a much higher, more macro level than quantum mechanics. Besides, randomness can be introduced into silicon if it's that important. I hope the article is misrepresenting his opinion, but they seem dangerously close to 'the brain is more complex than I can comprehend, so it must be magic'. I and many cognitive and neuroscientists I've spoken to consider this whole line of reasoning to be anti-scientific philosophy (although I may be biased because I studied AI, which rests on the idea that silicon can recreate intelligence).
- zepolud 14y ago
  Even a quantum system could be simulated on classical Turing machine so I fail to see how that relates to computability. The whole article boils down to a metaphysical, a-wizard-did-it, type of argument as usual.
- bascule 14y ago
  According to Max Tegmark's calculations, the importance of quantum mechanical effects on brain processes is negligible: http://arxiv.org/abs/quant-ph/9907009 http://arxiv.org/abs/quant-ph/9907009 This paper posits the brain can be modeled as a classical (e.g. Newtonian, "billiard ball"-style) physical system
  - api 14y ago
    This is based on the idea that the sum total of what the brain does can be explained by and represented by neural network type models. The conventional neural network model neglects the interior of the neuron. Gene regulatory networks for complex eukaryotes are on the order of neural networks in complexity and involve quantum-scale interactions, which opens the possibility of quantum effects being significant. Gene regulation within the neuron affects neural firing behavior and, more importantly, profoundly affects neural growth patterns and thus learning and longer term forms of cognition. This also neglects the possibility (now considered probable) that more cell types than just neurons are involved in brain activity: http://en.wikipedia.org/wiki/Gliotransmitter http://en.wikipedia.org/wiki/Gliotransmitter In short: the brain is not a neural network. Rather, those mathematical connectionist models are just that: models of aspects of the brain. We do not yet know to what extent these other mechanisms play a role, and what their role is. Given their nature it seems in both cases that their role might be more long-term, affecting long duration learning, planning, etc. It really seems to me as if the most ardent and enthusiastic adherents of the Kurzweilian vision are computer scientists who don't really respect the domain of biology and like to hand-wave away its complexity as "background noise." You can't do that. I say this as a lifelong computer programmer who has studied biology. Studying biology really blew away any notions I had of simple, classical computer programs becoming movie-style AI. The author is not making an anti-scientific "magic" argument. He is simply pointing out that biological systems are analog, embodied, electrochemical (and thus physical and possibly quantum), nonlinear complex systems, and he is being skeptical about the idea that such a system is going to yield readily to digital computer simulation. I agree with his skepticism. Prediction: brain simulations will simulate superficial brain behavior but they will not become sentient. More specific prediction: they will get stuck in closed cycle loops. They will not exhibit the higher order motivation, creativity, or learning behavior seen in brains, which is probably because these behaviors emerge from all the real embodied biophysical stuff the CS people are ignoring.
bmh100 14y ago
Is anyone familiar enough with this argument that they can lay down the premises? It is not clear what makes him think that the brain and, by extension, physics are not computable.
icegreentea 14y ago
I don't think the non-linearity argument is too convincing. Certainly, I accept that you cannot simulate a specific brain/mind - that is, if you somehow knew the exact structure and inner workings of a specific mind that you could then run a simulation of that mind which returns the same outputs as the original mind. I can buy that our simulations of non-linear problems will not fully match 'reality' and cause divergence. However, that doesn't mean we cannot run a model. Exactly what the model's output 'means'... well, that's a different question. To use his examples, our simulations of weather or the stock market do not produce the same output as the future. But their outputs (hopefully) represent actually realizable states of the world. In other words, as long as our model gives us 'human enough' output, then I guess it's sufficient? I mean, it really comes down to 'why do you want to simulate the human brain'. If you want to be able to upload your brain, then that probably isn't good enough. But I can imagine for various other uses, it could be enough. I do think Kurzweil is at best... wildly optimistic though.
mistercow 14y ago
>That’s because its most important features are the result of unpredictable, non-linear interactions amongst billions of cells, Nicolelis says. Replace "cells" with "molecules" and "consciousness" with "fluid dynamics", and you can see what a vague, hand-waving argument this is. >“You can’t predict whether the stock market will go up or down because you can’t compute it,” he says. “You could have all the computer chips ever in the world and you won’t create a consciousness.” You can't predict the precise behavior of an analog amplifier, either, but you can still model it and produce a digital equivalent.
- Aqueous 14y ago
  Right. Tell this to the field of meteorology, or any other discipline that uses computers to simulate chaotic systems. We simulate complex, non-linear systems with computers all the time. Just because we don't have the solution for the differential equation that describes these dynamics doesn't mean that we can't simulate them.
  - defen 14y ago
    The problem with chaotic systems isn't simulating them, it's measuring the initial conditions. Arbitrarily small differences blow up exponentially fast even if your simulation has really, really small time steps.
    - VMG 14y ago
      But does a model of a human neuron require that the initial conditions are perfectly captured? I can't see why it would.
      - defen 14y ago
        I have no idea :-) But I'm guessing the guy in the article thinks so, since he talks about non-linear effects. Linear systems cannot be chaotic.
    - Aqueous 14y ago
tibbon 14y ago
My girlfriend is a neuroscientist. Every time she sees something about them 'modeling the brain' she is visibly amused/unhappy. It might be possible, but our current understanding of the brain feels much further away. The concept that we're going to hit some moore's law style thing in science that will propel us to just automatically understand things, which we can barely measure currently, just doesn't line up. Just the process to understand how a single thing functions on a single channel seems to take forever now, and most neuroscience labs aren't limited by the speed of their desktops...
- Aqueous 14y ago
  Right, it takes forever now - and it took twice as long five years ago.
  - tibbon 14y ago
    But the thing is most neuroscientists don't just sit at a computer all day. 95% of the tasks they do are not computer-bound. If you're doing animal-based research (the majority of real neuroscience currently), then its time spent with behavior testing, surgeries, waiting for the drug to be in an animal for 72 (or however many) hours, processing slides, pipetting, etc. The time spent at a computer is mostly data analysis, reading papers, ordering supplies and grantwriting. A huge amount of time seems to be spent jumping through hoops, ordering things, working with vendors of equipment that doesn't frequently work as advertised, and dealing with broken stuff overall. The data-analysis they are doing again, isn't bound by the computer's speed. It generally is working with a few dozen (or hundred) samples of relatively computationally easy data. There's not much for a computer to speed up.
    - deleted 14y ago
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- bmh100 14y ago
  On the other hand, I believe we did see exponential growth in our ability to both automatically drive cars, to automatically translate text, and in voice recognition. If we consider 1958 to be a good starting point for self-driving cars (http://technologizer.com/2010/10/09/google-self-driving-cars/ http://technologizer.com/2010/10/09/google-self-driving-cars...), might we say that Google's car is orders of magnitude more powerful than those of 1986? If we consider 1954 a starting point for machine translation (https://en.wikipedia.org/wiki/History_of_machine_translation https://en.wikipedia.org/wiki/History_of_machine_translation), again might we find that Google Translate is similarly in a different league than SYSTRAN of the 1980s? I do not really have the knowledge and sources to back those claims up, so I have to frame them as opinions for now. Could someone with experiences or deeper knowledge about these areas weigh in?
Xcelerate 14y ago
I'm going to take the unpopular stance and say that it's very hard to make a prediction like this. Anyone who has a very strong stance one way or another probably needs to reevaluate their predictive capabilities. I do work in molecular dynamics. To even simulate a million atoms requires huge approximations. You can get more accurate as you simulate less. If you want an almost perfect match with reality, simulation will get you about 2-3 helium atoms. Now consider how many atoms are in a human brain. So it's hard for me to imagine fully simulating a human brain, although I don't see why it is theoretically impossible. Brains behave according to the same laws of physics as everything else in the universe. On our current technological improvement path, I don't see a brain simulation occurring any time soon. If quantum computers were developed, it would make things much easier, but we would still need a new "kind" of technology. I wouldn't rule it out completely though. Who in the 1600s would have predicted microprocessors? As for his talk about souls or consciousness, that just confuses me (and I'm religious too). Everything that we have thus far discovered obeys the laws of physics, so ruling out a simulation via some mystical "property" that human brains have seems sketchy to me. Now, if you want to talk about things that really aren't computable, I'll direct you to Chaitin's constant: http://en.wikipedia.org/wiki/Chaitins_constant http://en.wikipedia.org/wiki/Chaitins_constant
- muglug 14y ago
  As I understand it, currents attempts to simulate brain activity operate on a slightly higher scale, mimicking the behaviour of neurons and the electronic signals between them, without resorting to modelling the behaviour of individual atoms.
  - Xcelerate 14y ago
    Yeah... what I've found from my work is that higher-order modeling tends to leave out important effects. Which is okay when you're specifically trying to understand one particular property of a system (diffusivity, charge distribution, etc.), but when you want ALL properties to be accurate? That's difficult. Edit: I'll elaborate a little bit more. We currently simulate large proteins using force fields like CHARMM or AMBER. The problem we're trying to solve is what structure these proteins will fold into, and these force-fields work pretty well for that. But consider this: these potentials are basically a handful of equations that describe stretching, bending, torsional, van der Waals, and electrostatic interactions. The parameters for these equations come from measurements of simple compounds that have similar structure, and these are used to extrapolate what will happen in a different substance. Good enough for folding, but if you want accurate energy levels? No way.
Aqueous 14y ago
Of course the brain is computable. The brain is a computer.
- nisa 14y ago
  [citation needed]
  - Aqueous 14y ago
    The brain is made up of neurons. The neuron is a device that stores and processes information. Does it do so using a finite set of logical steps? We don't quite know yet, but it seems likely, since the behavior of the neuron has been shown to closely follow a known set of differential equations (the cable equations - http://en.wikipedia.org/wiki/Cable_theory http://en.wikipedia.org/wiki/Cable_theory). But using the broadest definition of a computer, a device that stores and processes information, the brain is most certainly a computer.
carwithcookies 14y ago
Has anyone seen a better critique of Kurzweil's "How To Create A Mind?" I'm reading it now and have been kind of hankering for an analysis to compare my own issues/questions with.
mehwoot 14y ago
I too believe this. Here is my argument: 1) If we have to simulate it at a low level, the human brain is far too complex for any computer in any timeframe of our current lives to have enough power to simulate properly 2) Working backwards and simulating the high level processes (AI, etc) have been a dismal failure at actually replicating human thought processes, and will continue to be. While NN or the like can theoretically simulate any algorithm, we have no idea how to effectively train them in a way that produces high level thought similar to a human brain. Generally when discussing this with people, I say this: if you disagree, give me a date by which you think I will be shown wrong, and then we'll reevaluate at that point. I fully expect I could be proven wrong, and that would be an awesome world to live in, but my bold and unfortunate prediction is that I won't be.
- VMG 14y ago
  > I too believe this. You don't. The article argues that there is a theoretical barrier that prevents a brain emulation in principle, you argue that technology isn't ready yet and won't be in our lifetimes. Opponents of your viewpoint argue that you simply can't imagine the state of technology in 50 years.
  - mehwoot 14y ago
    The subject is, "The Brain is Not Computable". I too believe that. The article itself is quite vague in what particular objections the guy has. It doesn't actually state he thinks it is not computable in theory, just in practice > That’s because its most important features are the result of unpredictable, non-linear interactions amongst billions of cells, Nicolelis says. If he thought it was theoretically impossible, then the "billions of cells" would be redundant. It would only take 1 un-computable cell. Without a longer interview, we can't be sure what exactly he means. My interpretation was "unpredictable, non-linear" (i.e. not computable by a simple algorithm, would have to be very complex, because of non linear interactions between inputs) amongst "billions of cells" = an obscene amount of computational data. I don't think he means unpredictable to mean strictly uncomputable. > Opponents of your viewpoint argue that you simply can't imagine the state of technology in 50 years. Yes, but at the same time there are things we thought we would be able to do 50 years ago that there is no way we can do now. There are physical constraints to the universe, and we can't just assume "technology" will overcome all of them. Nobody can imagine the state of technology in 50 years accurately, but I am still willing (and have done) to take bets on this 50 years into the future.
amalag 14y ago
Assuming the brain is an instrument or computer machine as many seem to be doing in the comments. Who is the operator of the machine?
api 14y ago
I'm somewhere in between. I think it might be possible to create a machine that does what the brain does, or even to "upload," though I don't see the latter anytime in the foreseeable future. But if so, I don't think it'll be with a standard von Neumann machine. Not that such a computer couldn't perform the required computations... it's Turing complete. But I think it would be a very poor fit for the problem domain. You'd want some kind of radically different incredibly highly parallel architecture. You also might want it to be analog or analog-like. There's been some interesting renewed interest in analog computers for a little while, and in probabilistic processors that can run incredibly fast by discarding the requirement of perfection.
JoeAltmaier 14y ago
tl;dr: guy says the brain is not computable. I say: Is too! Dialogue complete.
Vivtek 14y ago
Oh come on. I'm not going to make a prediction one way or the other, but there's one thing I do know: simulating the brain and simulating the current stock market to predict the outcome of a stochastic process (which is unknowable because you don't even know the inputs) are two vastly different things. So that's a really weak argument for his position. Not an argument for it at all, actually.
kristofferR 14y ago
I simply can't understand why people feel the need to proclaim that something plausible will never ever happen some time in the (possibly very distant) future. It's both stupid, unproductive and often embarrassing (when they are proven wrong). >"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. I'm guessing/hoping that the silicon reference was made by the author of the article and not Miguel Nicolelis, considering that silicon is extremely likely to be replaced by graphite or something else in the next decade or two, at least with almost full certainty by the next century. If it actually was Nicolelis who spoke about silicon, it automatically discredits him from having anything to say about the distant future of computing. >That’s because its most important features are the result of unpredictable, non-linear interactions amongst billions of cells, Nicolelis says." Even if that was true, which I doubt, so what? There has to be some kind of a system behind those "unpredictable, non-linear interactions" in order for the brain to have any functionality at all, and every system can be figured out and simulated. It might be incredibly complex and take centuries for us to gain the required knowledge and processing power, but even that doesn't make it impossible.
- JoeAltmaier 14y ago
  Agreed. The brain was 'invented' by non-intelligent evolution, a blind drunkard's walk of chemistry and biology. I am amazed we haven't figured out what mind-bogglingly simple premises are required to build a brain - it happened through a series of alway-stable always-useful small steps. I've seen a car designed by a web page through random 'genetic algorithm'. How about a simple random walk through neuron interconnection until something useful pops out?
aaron695 14y ago
LOL what total bunk, "unless" of course you practice some sort of magic and believe by definition humans cannot replicate this form of magic, then his theory might fit. Besides which the Singularity has nothing to do with the 'soul' and consciousness. It's about super intelligence, this is possible without being self aware. IE Deep Blue I assume is not considered 'conscious' but it can solve the chess problem better than us, why would you think a super intelligent machine that can solve general problems has to also be 'self aware', bizarre.
TeMPOraL 14y ago
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_questions/ http://lesswrong.com/lw/iu/mysterious_answers_to_mysterious_...
chevreuil 14y ago
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 http://www.actusf.com/spip/article-9802.html (sorry I can't find an English version)

39 points by petermlm 14y ago

Surely if you created a physics virtual machine and loaded an image with all of the atoms and electrons in place.. you'd simulate the brain. I imagine it would take a lot of computational power, but it's not 'never' Unless we're talking about souls here or something

seanmcdirmid 14y ago
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.
- comex 14y ago
  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.
  - seanmcdirmid 14y ago
    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.
    - comex 14y ago
      Why simulate? For immortality and what VMs call snapshots and cloning, of course. ;p
stefantalpalaru 14y ago
If we really need to simulate interactions at molecular level we're fracked. That kind of computational power is unimaginable.
- kristofferR 14y ago
  So was Petabytes 60 years ago, yet today there are people who have single-handedly uploaded more than that on private BitTorrent trackers. Never say never.

guylhem 14y ago

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 nanomachines that could read it from a "live" human - by broadcasting radio waves, or emitting photons (we started doing that for proteins with antibodies glued to radioactive markets, then we improved and glued them luciferase, now we do multiple colors and IIRC it's being experimented for DNA), whatever. Now imagine other nanomachines that could rearrange the microtubules to match that - voila, you've got Matrix-style "uploading" of knowledge once we understand how the memory bits interact with eachother, how they can be accessed by the subject. Maybe it's like a SQL database fk/pk - we don't know. But something must exist to allow it. When we figure it out, there is no reason why it couldn't be done too. My own predictions : after we confirm how memories are stored, if we have nanotechnologies to create nanomachines, we will start reading memories just like we did with DNA and proteins. It will take a while, we will only have a read-only access at first- and with many bugs just like how introns and TATA boxes could be mysterious initially - but we will understand in the end, and that will be half of the problem solved. Downloading will require additional advances in computer technology (at least faster cpus, in 3d instead of 2d to get more interconnections and raw computing power, and maybe some integration of processing and memory to match how neurons work), but it does not seem far-fetched to me.

kybernetikos 14y ago
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. http://en.wikipedia.org/wiki/Church%E2%80%93Turing%E2%80%93Deutsch_principle http://en.wikipedia.org/wiki/Church%E2%80%93Turing%E2%80%93D...
- 14y ago

rm999 14y ago

>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 predictability is important to the brain. While it's possible quantum effects could explain unpredictability in the physical universe, there is no scientific evidence this is relevant to the brain; the brain operates at a much higher, more macro level than quantum mechanics. Besides, randomness can be introduced into silicon if it's that important. I hope the article is misrepresenting his opinion, but they seem dangerously close to 'the brain is more complex than I can comprehend, so it must be magic'. I and many cognitive and neuroscientists I've spoken to consider this whole line of reasoning to be anti-scientific philosophy (although I may be biased because I studied AI, which rests on the idea that silicon can recreate intelligence).

zepolud 14y ago
Even a quantum system could be simulated on classical Turing machine so I fail to see how that relates to computability. The whole article boils down to a metaphysical, a-wizard-did-it, type of argument as usual.
bascule 14y ago
According to Max Tegmark's calculations, the importance of quantum mechanical effects on brain processes is negligible: http://arxiv.org/abs/quant-ph/9907009 http://arxiv.org/abs/quant-ph/9907009 This paper posits the brain can be modeled as a classical (e.g. Newtonian, "billiard ball"-style) physical system
- api 14y ago
  This is based on the idea that the sum total of what the brain does can be explained by and represented by neural network type models. The conventional neural network model neglects the interior of the neuron. Gene regulatory networks for complex eukaryotes are on the order of neural networks in complexity and involve quantum-scale interactions, which opens the possibility of quantum effects being significant. Gene regulation within the neuron affects neural firing behavior and, more importantly, profoundly affects neural growth patterns and thus learning and longer term forms of cognition. This also neglects the possibility (now considered probable) that more cell types than just neurons are involved in brain activity: http://en.wikipedia.org/wiki/Gliotransmitter http://en.wikipedia.org/wiki/Gliotransmitter In short: the brain is not a neural network. Rather, those mathematical connectionist models are just that: models of aspects of the brain. We do not yet know to what extent these other mechanisms play a role, and what their role is. Given their nature it seems in both cases that their role might be more long-term, affecting long duration learning, planning, etc. It really seems to me as if the most ardent and enthusiastic adherents of the Kurzweilian vision are computer scientists who don't really respect the domain of biology and like to hand-wave away its complexity as "background noise." You can't do that. I say this as a lifelong computer programmer who has studied biology. Studying biology really blew away any notions I had of simple, classical computer programs becoming movie-style AI. The author is not making an anti-scientific "magic" argument. He is simply pointing out that biological systems are analog, embodied, electrochemical (and thus physical and possibly quantum), nonlinear complex systems, and he is being skeptical about the idea that such a system is going to yield readily to digital computer simulation. I agree with his skepticism. Prediction: brain simulations will simulate superficial brain behavior but they will not become sentient. More specific prediction: they will get stuck in closed cycle loops. They will not exhibit the higher order motivation, creativity, or learning behavior seen in brains, which is probably because these behaviors emerge from all the real embodied biophysical stuff the CS people are ignoring.

bmh100 14y ago

Is anyone familiar enough with this argument that they can lay down the premises? It is not clear what makes him think that the brain and, by extension, physics are not computable.

icegreentea 14y ago

I don't think the non-linearity argument is too convincing. Certainly, I accept that you cannot simulate a specific brain/mind - that is, if you somehow knew the exact structure and inner workings of a specific mind that you could then run a simulation of that mind which returns the same outputs as the original mind. I can buy that our simulations of non-linear problems will not fully match 'reality' and cause divergence. However, that doesn't mean we cannot run a model. Exactly what the model's output 'means'... well, that's a different question. To use his examples, our simulations of weather or the stock market do not produce the same output as the future. But their outputs (hopefully) represent actually realizable states of the world. In other words, as long as our model gives us 'human enough' output, then I guess it's sufficient? I mean, it really comes down to 'why do you want to simulate the human brain'. If you want to be able to upload your brain, then that probably isn't good enough. But I can imagine for various other uses, it could be enough. I do think Kurzweil is at best... wildly optimistic though.

mistercow 14y ago

>That’s because its most important features are the result of unpredictable, non-linear interactions amongst billions of cells, Nicolelis says. Replace "cells" with "molecules" and "consciousness" with "fluid dynamics", and you can see what a vague, hand-waving argument this is. >“You can’t predict whether the stock market will go up or down because you can’t compute it,” he says. “You could have all the computer chips ever in the world and you won’t create a consciousness.” You can't predict the precise behavior of an analog amplifier, either, but you can still model it and produce a digital equivalent.

Aqueous 14y ago
Right. Tell this to the field of meteorology, or any other discipline that uses computers to simulate chaotic systems. We simulate complex, non-linear systems with computers all the time. Just because we don't have the solution for the differential equation that describes these dynamics doesn't mean that we can't simulate them.
- defen 14y ago
  The problem with chaotic systems isn't simulating them, it's measuring the initial conditions. Arbitrarily small differences blow up exponentially fast even if your simulation has really, really small time steps.
  - VMG 14y ago
    But does a model of a human neuron require that the initial conditions are perfectly captured? I can't see why it would.
    - defen 14y ago
      I have no idea :-) But I'm guessing the guy in the article thinks so, since he talks about non-linear effects. Linear systems cannot be chaotic.
  - Aqueous 14y ago

tibbon 14y ago

My girlfriend is a neuroscientist. Every time she sees something about them 'modeling the brain' she is visibly amused/unhappy. It might be possible, but our current understanding of the brain feels much further away. The concept that we're going to hit some moore's law style thing in science that will propel us to just automatically understand things, which we can barely measure currently, just doesn't line up. Just the process to understand how a single thing functions on a single channel seems to take forever now, and most neuroscience labs aren't limited by the speed of their desktops...

Aqueous 14y ago
Right, it takes forever now - and it took twice as long five years ago.
- tibbon 14y ago
  But the thing is most neuroscientists don't just sit at a computer all day. 95% of the tasks they do are not computer-bound. If you're doing animal-based research (the majority of real neuroscience currently), then its time spent with behavior testing, surgeries, waiting for the drug to be in an animal for 72 (or however many) hours, processing slides, pipetting, etc. The time spent at a computer is mostly data analysis, reading papers, ordering supplies and grantwriting. A huge amount of time seems to be spent jumping through hoops, ordering things, working with vendors of equipment that doesn't frequently work as advertised, and dealing with broken stuff overall. The data-analysis they are doing again, isn't bound by the computer's speed. It generally is working with a few dozen (or hundred) samples of relatively computationally easy data. There's not much for a computer to speed up.
  - deleted 14y ago
    [deleted]
bmh100 14y ago
On the other hand, I believe we did see exponential growth in our ability to both automatically drive cars, to automatically translate text, and in voice recognition. If we consider 1958 to be a good starting point for self-driving cars (http://technologizer.com/2010/10/09/google-self-driving-cars/ http://technologizer.com/2010/10/09/google-self-driving-cars...), might we say that Google's car is orders of magnitude more powerful than those of 1986? If we consider 1954 a starting point for machine translation (https://en.wikipedia.org/wiki/History_of_machine_translation https://en.wikipedia.org/wiki/History_of_machine_translation), again might we find that Google Translate is similarly in a different league than SYSTRAN of the 1980s? I do not really have the knowledge and sources to back those claims up, so I have to frame them as opinions for now. Could someone with experiences or deeper knowledge about these areas weigh in?

Xcelerate 14y ago

I'm going to take the unpopular stance and say that it's very hard to make a prediction like this. Anyone who has a very strong stance one way or another probably needs to reevaluate their predictive capabilities. I do work in molecular dynamics. To even simulate a million atoms requires huge approximations. You can get more accurate as you simulate less. If you want an almost perfect match with reality, simulation will get you about 2-3 helium atoms. Now consider how many atoms are in a human brain. So it's hard for me to imagine fully simulating a human brain, although I don't see why it is theoretically impossible. Brains behave according to the same laws of physics as everything else in the universe. On our current technological improvement path, I don't see a brain simulation occurring any time soon. If quantum computers were developed, it would make things much easier, but we would still need a new "kind" of technology. I wouldn't rule it out completely though. Who in the 1600s would have predicted microprocessors? As for his talk about souls or consciousness, that just confuses me (and I'm religious too). Everything that we have thus far discovered obeys the laws of physics, so ruling out a simulation via some mystical "property" that human brains have seems sketchy to me. Now, if you want to talk about things that really aren't computable, I'll direct you to Chaitin's constant: http://en.wikipedia.org/wiki/Chaitins_constant http://en.wikipedia.org/wiki/Chaitins_constant

muglug 14y ago
As I understand it, currents attempts to simulate brain activity operate on a slightly higher scale, mimicking the behaviour of neurons and the electronic signals between them, without resorting to modelling the behaviour of individual atoms.
- Xcelerate 14y ago
  Yeah... what I've found from my work is that higher-order modeling tends to leave out important effects. Which is okay when you're specifically trying to understand one particular property of a system (diffusivity, charge distribution, etc.), but when you want ALL properties to be accurate? That's difficult. Edit: I'll elaborate a little bit more. We currently simulate large proteins using force fields like CHARMM or AMBER. The problem we're trying to solve is what structure these proteins will fold into, and these force-fields work pretty well for that. But consider this: these potentials are basically a handful of equations that describe stretching, bending, torsional, van der Waals, and electrostatic interactions. The parameters for these equations come from measurements of simple compounds that have similar structure, and these are used to extrapolate what will happen in a different substance. Good enough for folding, but if you want accurate energy levels? No way.

Aqueous 14y ago

Of course the brain is computable. The brain is a computer.

nisa 14y ago
[citation needed]
- Aqueous 14y ago
  The brain is made up of neurons. The neuron is a device that stores and processes information. Does it do so using a finite set of logical steps? We don't quite know yet, but it seems likely, since the behavior of the neuron has been shown to closely follow a known set of differential equations (the cable equations - http://en.wikipedia.org/wiki/Cable_theory http://en.wikipedia.org/wiki/Cable_theory). But using the broadest definition of a computer, a device that stores and processes information, the brain is most certainly a computer.

carwithcookies 14y ago

Has anyone seen a better critique of Kurzweil's "How To Create A Mind?" I'm reading it now and have been kind of hankering for an analysis to compare my own issues/questions with.

mehwoot 14y ago

I too believe this. Here is my argument: 1) If we have to simulate it at a low level, the human brain is far too complex for any computer in any timeframe of our current lives to have enough power to simulate properly 2) Working backwards and simulating the high level processes (AI, etc) have been a dismal failure at actually replicating human thought processes, and will continue to be. While NN or the like can theoretically simulate any algorithm, we have no idea how to effectively train them in a way that produces high level thought similar to a human brain. Generally when discussing this with people, I say this: if you disagree, give me a date by which you think I will be shown wrong, and then we'll reevaluate at that point. I fully expect I could be proven wrong, and that would be an awesome world to live in, but my bold and unfortunate prediction is that I won't be.

VMG 14y ago
> I too believe this. You don't. The article argues that there is a theoretical barrier that prevents a brain emulation in principle, you argue that technology isn't ready yet and won't be in our lifetimes. Opponents of your viewpoint argue that you simply can't imagine the state of technology in 50 years.
- mehwoot 14y ago
  The subject is, "The Brain is Not Computable". I too believe that. The article itself is quite vague in what particular objections the guy has. It doesn't actually state he thinks it is not computable in theory, just in practice > That’s because its most important features are the result of unpredictable, non-linear interactions amongst billions of cells, Nicolelis says. If he thought it was theoretically impossible, then the "billions of cells" would be redundant. It would only take 1 un-computable cell. Without a longer interview, we can't be sure what exactly he means. My interpretation was "unpredictable, non-linear" (i.e. not computable by a simple algorithm, would have to be very complex, because of non linear interactions between inputs) amongst "billions of cells" = an obscene amount of computational data. I don't think he means unpredictable to mean strictly uncomputable. > Opponents of your viewpoint argue that you simply can't imagine the state of technology in 50 years. Yes, but at the same time there are things we thought we would be able to do 50 years ago that there is no way we can do now. There are physical constraints to the universe, and we can't just assume "technology" will overcome all of them. Nobody can imagine the state of technology in 50 years accurately, but I am still willing (and have done) to take bets on this 50 years into the future.

amalag 14y ago

Assuming the brain is an instrument or computer machine as many seem to be doing in the comments. Who is the operator of the machine?

api 14y ago

I'm somewhere in between. I think it might be possible to create a machine that does what the brain does, or even to "upload," though I don't see the latter anytime in the foreseeable future. But if so, I don't think it'll be with a standard von Neumann machine. Not that such a computer couldn't perform the required computations... it's Turing complete. But I think it would be a very poor fit for the problem domain. You'd want some kind of radically different incredibly highly parallel architecture. You also might want it to be analog or analog-like. There's been some interesting renewed interest in analog computers for a little while, and in probabilistic processors that can run incredibly fast by discarding the requirement of perfection.

JoeAltmaier 14y ago

tl;dr: guy says the brain is not computable. I say: Is too! Dialogue complete.

Vivtek 14y ago

Oh come on. I'm not going to make a prediction one way or the other, but there's one thing I do know: simulating the brain and simulating the current stock market to predict the outcome of a stochastic process (which is unknowable because you don't even know the inputs) are two vastly different things. So that's a really weak argument for his position. Not an argument for it at all, actually.

kristofferR 14y ago

I simply can't understand why people feel the need to proclaim that something plausible will never ever happen some time in the (possibly very distant) future. It's both stupid, unproductive and often embarrassing (when they are proven wrong). >"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. I'm guessing/hoping that the silicon reference was made by the author of the article and not Miguel Nicolelis, considering that silicon is extremely likely to be replaced by graphite or something else in the next decade or two, at least with almost full certainty by the next century. If it actually was Nicolelis who spoke about silicon, it automatically discredits him from having anything to say about the distant future of computing. >That’s because its most important features are the result of unpredictable, non-linear interactions amongst billions of cells, Nicolelis says." Even if that was true, which I doubt, so what? There has to be some kind of a system behind those "unpredictable, non-linear interactions" in order for the brain to have any functionality at all, and every system can be figured out and simulated. It might be incredibly complex and take centuries for us to gain the required knowledge and processing power, but even that doesn't make it impossible.

JoeAltmaier 14y ago
Agreed. The brain was 'invented' by non-intelligent evolution, a blind drunkard's walk of chemistry and biology. I am amazed we haven't figured out what mind-bogglingly simple premises are required to build a brain - it happened through a series of alway-stable always-useful small steps. I've seen a car designed by a web page through random 'genetic algorithm'. How about a simple random walk through neuron interconnection until something useful pops out?

aaron695 14y ago

LOL what total bunk, "unless" of course you practice some sort of magic and believe by definition humans cannot replicate this form of magic, then his theory might fit. Besides which the Singularity has nothing to do with the 'soul' and consciousness. It's about super intelligence, this is possible without being self aware. IE Deep Blue I assume is not considered 'conscious' but it can solve the chess problem better than us, why would you think a super intelligent machine that can solve general problems has to also be 'self aware', bizarre.

TeMPOraL 14y ago

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

chevreuil 14y ago

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 http://www.actusf.com/spip/article-9802.html (sorry I can't find an English version)