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The computational power of the human brain

frontiersin.org

21–30 of 44 posts

Re: The computational power of the human brain

#21
post #6

Earlier quoted context omitted.

Insightful. And the next era will describe it in terms of quantum interactions.

> Insightful. And the next era will describe it in terms of quantum interactions. Roger Penrose already talks about a theory of consciousness based on non-computable quantum effects in microtubules. http://www.consciousentities.com/penrose.htm

Keep in mind that this is probably (a) bollocks, and (b) doesn't preclude brains being (quantum) computers.

You can use a Turing machine to (inefficiently) simulate a quantum computer just fine.

The page you linked to also seems to think that Gödel's incompleteness theorem says that human brains can do thinks that computers can't. That conclusion isn't warranted:

Yes, there are specific statements that specific formal systems can neither prove nor disprove. And for every formal system you can find such systems.

However, there are also plenty of statements that humans can neither prove nor disprove. Human also make plenty of mistakes. (You can also build a probabilistic formal system that's allowed to make mistakes.)

Re: The computational power of the human brain

#22

This kind of question is meaningless, and I’m pretty sure it comes from the old view of neurons being somewhat akin to a 1-1 or many-1 digital switch (it isn’t). In fact, we currently don’t even know the full extent of the types of neurons in the brain or the way they function and interact [1] There are neurons that only fire when a certain percentage of their inputs are stimulated, some that have a temporal componen…

Yes Walter Pitt's proposal, which he disproved. But we know the prefrontal cortex is capable of simulating a turing machine, or any machine for that matter.

Re: The computational power of the human brain

#23

> The brain has always been compared with a highly sophisticated computer. This is not strictly true. In ancient times, Plato compared the mind to a chariot pulled by two horses, representing emotion and reason. This reflected the importance of horses for transportation at the time. In the 1600s, Descartes saw the mind as akin to a mechanical clockwork machine, reflective of the clockwork and automatons built then. I…

Yeah, "always" is always problematic when making gross comments about the world

Re: The computational power of the human brain

#24

Earlier quoted context omitted.

True, but there was Ben-Hur's thesis that "a chariot is capable of carrying any person", which says as much about brains as the Church-Turing thesis does unless you beg the question.

Do you mean that it's begging the question to assume that the brain comes to its conclusions via a physically deterministic procedure that terminates in finite time?

That's not what the Church-Turing thesis is about. The Church-Turing thesis says that any "effective procedure" (i.e. algorithm) for performing computations on natural numbers is equivalent to a Turing machine. It is generally accepted but cannot be proven because "effective procedure" is not defined. Indeed it can be seen as providing a definition for the term "effective procedure".

To extend that to say anything about the physical world (i.e. some form of "Physical Church-Turing Thesis") is to make quite a different assertion and one that is not so "generally accepted". To make it say anything about brains you have to assert some form of equivalence between brains and "effective procedures" on the natural numbers, which is indeed to beg the question in this instance.

There's a different idea you may be confusing it with, which is the idea that since the known laws of physics (aside from state vector reduction in quantum mechanics) are in the form of differential equations that can be numerically integrated to arbitrary precision anything can be "simulated". However, this is not part of the Church-Turing thesis. (And personally I find the phrase "to arbitrary precision" here, and the exception for state vector reduction, quite a barrier to basing any assertions about the nature of the universe or minds on it.)

Re: The computational power of the human brain

#25

> The brain has always been compared with a highly sophisticated computer. This is not strictly true. In ancient times, Plato compared the mind to a chariot pulled by two horses, representing emotion and reason. This reflected the importance of horses for transportation at the time. In the 1600s, Descartes saw the mind as akin to a mechanical clockwork machine, reflective of the clockwork and automatons built then. I…

Iain McGilchrist puts the matter of our lopsided repertoire of metaphors for the brain well in The Master and His Emissary (apologies for the lengthy quote):

> This leads to a fundamental point about any attempt to understand the brain. It is a particularly acute case of the problems encountered in understanding anything. The nature of the attention one brings to bear on anything alters what one finds; what we aim to understand changes its nature with the context in which it lies; and we can only ever understand anything as a something.

> There is no way round these problems—if they are problems. To attempt to detach oneself entirely is just to bring a special kind of attention to bear which will have important consequences for what we find. Similarly we cannot see something without there being a context, even if the context appears to be that of ‘no context’, a thing ripped free of its moorings in the lived world. That is just a special, highly value-laden kind of context in itself, and it certainly alters what we find, too. Nor can we say that we do not see things as anything at all—that we just see them, full stop. There is always a model by which we are understanding, an exemplar with which we are comparing, what we see, and where it is not identified it usually means that we have tacitly adopted the model of the machine.

>

> Such considerations apply to the attempt to understand anything at all. But when we come to look at what we refer to as brain functions, there is a problem of a wholly different order. We are not ‘just’ looking at things in the world—a lump of rock, or even a person—but the processes whereby the world itself, together with the rock or the person, might be brought into being for us at all, the very foundations of the fact of our experience, including any idea we might have about the nature of the world, and the nature of the brain, and even the idea that this is so. If it is true that attention changes the nature of what we find, how do we decide the most appropriate attention for that? One that tries to ignore the inwardness of experience? What possible context is there in which to place the foundations of experience of all contexts whatever? And what kind of a thing are we to see it ‘as’? The answer is far from obvious, but in the absence of an attempt to address the question we do not give no answer. We answer with the model we understand—the only kind of thing we can ever fully understand, for the simple reason that we made it: the machine.

Re: The computational power of the human brain

#26
If you know how sensory organs encode information as spike trains and the many ways neurons input, process and output signals, there's no way around the hypothesis that the brain does information processing. Denying that is just trying to sound clever by pattern-matching to the standard "it's all relative to our culture" criticism, and it's completely divorced from any actual evidence.

Re: The computational power of the human brain

#27
post #26

If you know how sensory organs encode information as spike trains and the many ways neurons input, process and output signals, there's no way around the hypothesis that the brain does information processing. Denying that is just trying to sound clever by pattern-matching to the standard "it's all relative to our culture" criticism, and it's completely divorced from any actual evidence.

Except that for the most part we don't know "how sensory organs encode information as spike trains". This is the problem of "neural coding" and is very much at the stage of unproven hypotheses.

Meanwhile we have abundant evidence that continuous variables such as the precise timing of individual spikes have physiological effects.

Re: The computational power of the human brain

#28
post #5

Earlier quoted context omitted.

You are very right, but I still see a technological asymptote. What is said that the mind is like a computer is because it is based on logic, mathematics. The analogies may be to the latest current technology but they have one thing in common and it is the abstraction of a perfect machine or system, {We have little of perfect, but our mistakes make us unique and essential}

I don’t think that holds though because logic is a high level function of the brain not something fundamental to its design.

Depends on whether you think mathematical reasoning is uncovering fundamental tenets of reality. I think it is, and the history of experimental physics in particular supports this too.

Re: The computational power of the human brain

#29
post #26

If you know how sensory organs encode information as spike trains and the many ways neurons input, process and output signals, there's no way around the hypothesis that the brain does information processing. Denying that is just trying to sound clever by pattern-matching to the standard "it's all relative to our culture" criticism, and it's completely divorced from any actual evidence.

Except that for the most part we don't know "how sensory organs encode information as spike trains". This is the problem of "neural coding" and is very much at the stage of unproven hypotheses. Meanwhile we have abundant evidence that continuous variables such as the precise timing of individual spikes have physiological effects.

That's just rejecting information processing by one descriptive system and pretending another isn't information processing. Analog computers are possible, just difficult to build and make reproducible in a useful way for mankind.

But then of course, any analog process can be simulated by a sufficiently high fidelity digital one (i.e. digital music encoding). So all you've really got to is "it might take a considerably more powerful computer to fully reproduce the analog effects of human consciousness".

Re: The computational power of the human brain

#30
Separately but related: decades ago, research was done into the "Bandwidth of Consciousness", that is: how much information can we consciously process. That research came up with the startling low number of about 40 bits per second _at_most_. Suggesting that the huge amount of information our senses take in is massively compressed before we become 'conscious' of it.

References:

W R Garner and Harold W Lake "The Amount of Information in Absolute Judgements" - Psychological Review 58 (1951) - they attempted to measure people's ability to distinguish stimuli (such as light and sound) in bits. Result: 2.2 to 3.2 bits per second.

W E Hick "On the Rate of Gain of Information" - Quarterly Journal of Experimental Psychology 4 (1952) - this experiment measured how much information a person could pass on if they acted as a link in a communication channel. That is, faced with a series of flashing lights, subjects had to press the right keys. Result: 5.5 bits per second.

Henry Quastler "Studies of Human Channel Capacity" - Information Theory, Proceedings of the Third London Symposium (1956). Measured how many bits of information are expressed by a pianist while pressing keys on a piano. Result: 25 bits per second.

J R Pierce "Symbols, Signals and Noise" (Harper 1961) - used experiments involving letters and symbols. Result: 44 bits per second.

Mostly they are measuring bandwidth as being 'what can someone take in and then act on' and probably the 'acting on' bit is the bottleneck. I think this is an area of research that could do with being revisited, perhaps someone could devise a way of measuring bandwidth-in to consciousness vs bandwidth-out.

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