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Why Is the Human Brain So Efficient? (2018)

nautil.us

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Re: Why Is the Human Brain So Efficient? (2018)

#161

Post by the_af »

Stupulous wrote: post #108
the_af wrote: post #57

Earlier quoted context omitted.

Before CPUs existed, we would compare brains to steam engines. There was a very interesting article posted here on HN a while ago, explaining why humans always pattern match their understanding of the "mind" (or "soul") to whatever technology is fashionable in their time: steam engines, computers, etc. It also explained the pitfalls of doing so. I think there is at this time no indication human brains are in any way…

But steam engines and hydraulics and gear mechanisms are all Turing complete. There is nothing wrong with those models. You could build a brain out of any of them, unless the brain computes something that is not computable. If the brain does something that is not computable, that's a direct challenge to some of our most established science. It is possible, but I think very unlikely.

> You could build a brain out of any of them, unless the brain computes something that is not computable.

Could you? That's sort of begging the question. We do not know if something "Turing complete" can be used to build a brain like the human brain. That's precisely the point.

> If the brain does something that is not computable, that's a direct challenge to some of our most established science.

A challenge for computational neuroscience maybe. Otherwise I don't see the challenge for neither neuroscience nor computer science. If someone wants to make the claim you can build a human brain out of something Turin-machine-like, that's an extraordinary claim, not established science.

Re: Why Is the Human Brain So Efficient? (2018)

#162

Post by criddell »

catalogia wrote: post #135
SomeoneFromCA wrote: post #104

Earlier quoted context omitted.

Not a quantum physicists, but IMO Bekenstein bound is not applicable here, because quantum laws are non-deterministic, therefore you can describe the structure of a system, but you cannot describe how it will evolve. Quantum randomness might be in the very essence of how the brain and mind works.

Quantum randomness being necessary hardly seems like it would have profound practical implications since augmenting a digital computer with a geiger counter would be trivial.

It's much easier than that. Hardware random number generators are often based on something like a reverse-biased diode. Electrons migrate across and it's entirely random when it happens. Amplify and count them and you get a great source of entropy.

Re: Why Is the Human Brain So Efficient? (2018)

#163

Post by rland »

EmilioMartinez wrote: post #154
rland wrote: post #143

Earlier quoted context omitted.

Reaction time and the physical operation of the body are things that seem obvious to me. Try to design a control system for a machine that could replicate a gymnast, for example.

Sorry, but in my book responsiveness and functionality doesn't have a thing to do with accuracy (neither does parallelism if I may throw it in there).

Well, I guess I don't know what you mean by accuracy, then. I'm thinking of the accuracy required to hit the right note in a guitar solo, or the accuracy required to time a clean & jerk correctly, or the accuracy required to track a fast-moving object with the eye.

Those things can be surpassed by machines, of course, but if you wanted to design a machine to do all of them? With human efficiency?

Re: Why Is the Human Brain So Efficient? (2018)

#164

Post by PeterisP »

dTal wrote: post #159
TeMPOraL wrote: post #158

Earlier quoted context omitted.

I'm not convinced real neurons are just binary summators. But regardless of that, there's also chemical transmission involved, which is an analog thing.

Right, but the end state of all that is "neuron fires" or "neuron doesn't fire", or at best "neuron fires n times per second" - a binary state.

We have some behavior that depends on very exact timing of neuron spikes (e.g. determining direction of sounds by connecting signals from both ears), so that's kind of analog - though it does get reduced into a binary state, in the end either the "detector for offset of x microseconds towards left" fires or not.

Re: Why Is the Human Brain So Efficient? (2018)

#165

Post by PeterisP »

coreyp_1 wrote: post #49
The_rationalist wrote: post #23

Earlier quoted context omitted.

Comparing Human Brain with a CPU is misconception. no it is not. Yeah architecturally they are very different and CPU are arguably more programmable / general and less efficient. What does matter is whether CPUs are theoretically able to achieve all the things that a brain can do (and even more) And indeed CPUs as turing complete, programmable machine are a strict superset of what brains can do. The gap between what…

"And indeed CPUs as turing complete, programmable machine are a strict superset of what brains can do." This is a fundamental assertion that I do not believe you can make. The brain cannot simulate a turing machine. It does not have infinite memory, which is a requirement for a turing machine. It can, however, stimulate a linearly bounded automata. It is also not implicitly obvious that a turing machine can simulate…

If you go to a sufficiently high precision, neurons and their communication are discrete - the number of neurotransmitter molecules and ions transferred across any synapse is countable, so the number of states (even if we ignore noise and noise tolerance, which we shouldn't ignore) is finite.

Re: Why Is the Human Brain So Efficient? (2018)

#166

Post by PeterisP »

SomeoneFromCA wrote: post #51
sooheon wrote: post #43

Earlier quoted context omitted.

Biology is the ultimate legacy software running on one of the oldest platforms ever developed, the organic compounds. It is literally a giant genetic algorithm to write instructions (DNA) for manufacturing molecular machines (proteins) that interact with each other in an extremely complex graph of relations (protein pathways, i.e. control flow).

This a very simplistic view, based on assumption that the world is discrete. The whole idea of software relies on the concept of digital computer, a discrete machine. The world might indeed be analogous and real numbers might actually exist.

DNA and proteins are obviously discrete, so even if the hardware relies on some fundamental analogous behavior, the 'software' and each hardware component can still be analyzed as discrete behavior.

However, for anything operating at human temperatures we can reasonably assume that any effective behavior can be simulated by discrete operations, as any nuances of fundamental analogousness would be drowned by thermal noise and the amount of precision that any behavior can require is rather low, much lower than e.g. any standard floating point number in a discrete CPU.

Re: Why Is the Human Brain So Efficient? (2018)

#167

Post by benibela »

ALittleLight wrote: post #121
jbay808 wrote: post #97

Earlier quoted context omitted.

I remember when I first took a data structures course, learning things like trees and linked lists, I had a total paradigm shift with respect to how I understood my own mind. I had never really thought about the different ways that data could be organized, and how they perform differently. I figured that since this was so basic to computer science, my own mind couldn't be doing something completely different. It migh…

Recently I was thinking about how my brain answers the question "What's your favorite movie?" and how I can easily answer that question, but it's harder to answer a question like "What's your favorite movie where a gun is fired?" It seems to me that whenever I watch a movie, if I really liked it, I check my perceived quality of the movie against the quality of my current favorite movie, and if the new movie beats the…

>Recently I was thinking about how my brain answers the question "What's your favorite movie?" and how I can easily answer that question,

I can hardly answer that question

I think I need to make a table of all movies I watched, with columns for different quality aspects, and then I could calculate a score for all movies. Then the favorite movie has the highest score.

Then I think a few minutes about the table, before answering that I do not really have a favorite movie

Re: Why Is the Human Brain So Efficient? (2018)

#168

Post by deepnotderp »

anchpop wrote: post #133
deepnotderp wrote: post #109

Earlier quoted context omitted.

Isn't the recent Google quantum "supremacy" experiment evidence against the extended Church-Turing thesis?

No, quantum computers as we understand them can be simulated by a turing machine

The extended Church-Turing thesis which I specifically referred to concerns efficient simulation, not just whether it can be simulated.

Re: Why Is the Human Brain So Efficient? (2018)

#169

Post by HarHarVeryFunny »

"At a global level, the architectures of the brain and the computer resemble each other, consisting of largely separate circuits for input, output, central processing, and memory."

This is fundamentally wrong, even at the 10 mile high summary level.

In our brain processing and memory are not in the least bit separate, and memory distinct from processing doesn't really exist.

If you really had to make a computer analogy of how the brain works, it's more like self-modifying code where the only memory of the data flowing through it is the changes to the code that were made as the result of that prior flow.

Re: Why Is the Human Brain So Efficient? (2018)

#170

Post by otabdeveloper4 »

mannykannot wrote: post #53
otabdeveloper4 wrote: post #40

Earlier quoted context omitted.

The human brain isn't Turing-complete. Turing completeness implies infinite recursion, which the brain obviously can't do.

While I agree that comparing a human brain or mind to a Turing machine is not helpful, the objection you make here is less significant than it first appears. There is a subtle difference between unbounded recursion, which a Turing machine is taken to be capable of, and the actual ability to achieve infinite recursion. In no application of a Turing machine, either as an actual physical device or as a hypothetical one…

> For all practical and theoretical purposes, what matters is that the machine being considered does not exhaust its ability to recurse while performing the computations being considered.

You're right, and thanks for the more strict definition.

Regardless, the 'recursion limit' of the human brain is really low. (Say, seven things at once or thereabout; not going to links proofs but it's a non-controversial statement.)

Certainly not enough to implement any sort of computing machine. Human brains are notoriously bad at arithmetic and state machines.

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