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Comment by aristofun | Hacker News Reader

There is no direct parallels. And guess what - the brain is not even a computer.

Everything this was just metaphors for non experts, irrelevant contexts and making money on pseudo science books.

I think that very much depends on how you define "computer". the brain is doing computations, so I think it's safe to think of it as a computer. it's just a completely alien computer to what we build ourselves

By computation, do you mean problem solving? The most simplistic model I have of the brain (not a psychologist, just from thing I read) is that the brain is an advanced pattern matcher. I don't think we even do linear "computation", just because of the quantity of data we are ingesting, storing and retrieving.

how would you do pattern matching without computations?

I think anything that could be described through logic gates or turning machines would be a "computation". And any object or organ that processes information would be a "computer "

Because things are just are. An analogy I can come with is a graph like irrigation canals. You fill them with water and they just are. Or something like an adder circuits. You "input" the numbers and the result is just there. There isn't an algorithmic process with loops, conditions and recursions. We don't store information, we store its patterns and link it to other patterns. We don't process information as much as we filter it through patterns we've stored. Like logic gates do not process electricity, our brain do not process information.

(This is very much armchair psychology theory)

I'm not seeing the distinction. All computation "just is". computation happens through the physical world. adder circuits are performing a computation. an x86 CPU is nothing but a bunch of dumb circuits. water canals can do computations just like electrical circuits. as can biological neurons.

This is a computer with all the abstractions stripped away [1]. It's hard to see the loops and conditionals from the falling marbles, but it is processing information. And electrical computers are essentially the same thing, just scaled up to an unimaginable degree

[1] https://www.youtube.com/watch?v=8BOvLL8ok8I

At every point in history, people thought that they could describe the brain using whatever advanced technology they had.

<https://aeon.co/essays/your-brain-does-not-process-informati...>

Read the comments on that link for a summary of my thoughts.

> But neither the song nor the poem has been ‘stored’ in it. The brain has simply changed in an orderly way that now allows us to sing the song or recite the poem under certain conditions

Oof

> the brain is doing computations

Nope. We don't really know yet what exactly the brain is "doing".

But again, in _some_ contexts it is better than nothing.

Unfortunately good metaphors stick, regardless of their relevance and accuracy :(

there are a lot of mysteries around the brain, but at a high level, I think you'd have a hard time finding a neuroscientist who doesn't believe the brain processes information. what's the alternative?

Processing information is pretty vague and generic idea. You can label virtually anything as “processing information” and be more or less true.

But I doubt i find any neuroscientist worth anything who say “brain is doing computations almost like a computer”.

Like I said, it depends very much on how you define computer. To me "processing information" == "computation". And a physical system that performs "computations" is a computer. Therefore, a brain is just one type of biological computer.

In a computer science class, the first thing they should teach is that the word "computer" in the course name is abstract, and not just about the metal slab on your desk. There are fundamental laws that apply to all information processing systems, whether electrical, mechanical, or biological. So it makes sense to put them in the same category at times.

But obviously words mean different things in different contexts, and "computer" might mean something entirely different to a neuroscientist than a computer scientist. But I don't think a neuroscientist would disagree that a brain is a computer using the loose definition I described above

Of course, you can set up a definition space so that a puppy is a steam engine.

But if we stick to commonly adopted definitions, like https://en.wikipedia.org/wiki/Computer or "turing machine" ones - then NO, sorry, brain and computer has barely anything in common. Besides being made of atoms and being complex )

So it sounds like we both agree the brain is at least a physical object that performs computations. I'm surprised you don't see similarities with other physical systems that perform computations, but sounds like a terminology difference

Here is the heart of our disagreement:

> perform computations

Brain doesn’t perform computations in any CS accepted sense (neither it is a turing machine nor it has any encoded program to execute any defined algorithm).

It processes information, yes. But anything more specific than that is full of unknowns, unconfirmed hypothesis and speculations.

Would you call an ants colony a computer? A tree? A government? But they all obviously processes information and seemingly perform computations, don’t they?

> Brain doesn’t perform computations in any CS accepted sense (neither it is a turing machine nor it has any encoded program to execute any defined algorithm).

That's a big statement. Anything that can be effectively described with math, can be described using Turing machines and algorithms. Any Turing-complete system is equivalent. As far as we know, all of physics can be described by equations, therefore is (theoretically) computable. What makes you think brains are special? Are there any other physical systems that you think are uncomputable?

The only arguments I've found for why the brain can't be described by algorithms go into unconvincing pseudo-scientific arguments about the magic of quantum mechanics, which I find very unconvincing (quantum algorithms are still algorithms, and describable through math after all). Do you have a better one?

> Would you call an ants colony a computer? A tree? A government? But they all obviously processes information and seemingly perform computations, don’t they?

Yes, absolutely. You can use ant colonies or slime molds as biological computers to solve real-world finding problems: https://www.youtube.com/watch?v=BZUQQmcR5-g&t=1s

Some of your other examples are more complicated, but all of them can be described through the computational lens, and modeled as Turing machines. you will find many scientific papers filled with equations trying to describe the algorithms behind each of them

okay, we came to conclusion that almost any living organism can be called a computer

then what's the point in using this term if it doesn't differentiate anything?

it becomes meaningless, therefore there is no value in calling the brain a computer - it gives zero information about how brain actually works

case closed )

Because calling it a computer means you can apply computer science concepts to it. That's the interesting part. You can talk about the classes of algorithms the brain uses to solve difficult problems, the ways it tries to conserve energy, the architecture trade offs, how to model it with math, etc. That stuff is non-obvious if you treat it like a magic black box. It's not a meaningless insight

Can the brain solve NP problems in polynomial time? The brain itself is a mystery, but we know some things about computation, so it's pretty safe to say no, it cannot.

Maybe on HN it's consensus that all living things are computers in this way, but plenty of people think the brain is literally supernatural. By saying "the brain nothing in common with a computer. We don't know what it's doing", those people will be nodding their heads. But we do know some things about computation, so we can apply those insights to the brain

> You can talk about the classes of algorithms the brain uses to solve difficult problems

> But we do know some things about computation, so we can apply those insights to the brain

You can.

But it is a snake oil, it doesn't give you any actual insight on how brain really works.

To be able to model something with computer doesn't mean it is like a computer.

But at the same time such thinking can really confuse unprepared mind that brain is really modeled by nature as some sort of sophisticated turing machine.

This is misleading.

At the same time, pretending that brains don't obey the laws of computation has its own implications, which can confuse unprepared minds into thinking:

1) That brains are something supernatural, instead of physical information processing systems that can be analyzed and understood as such.

2) That digital turing-complete computers are limited and can't possibly do the kinds of complex processing that biological computers can do

Which is also misleading

A brain is not a Turing machine, but a Turing machine can be a brain. Biological brains are just a subset in the space of all possible computers

But I don't think either of us is confused, so this is just a conversation about the semantics, which I'm not very interested in

> A brain is not a Turing machine, but a Turing machine can be a brain.

At this point I regret I wasted my time explaining what's wrong with your reasoning :)

Peace!

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