PixyMisa, I'm sorry I got off on another tangent there.
I will try to behave and stay focused on the question.
So let's back up, if you don't mind.
The question I posed was essentially this:
What do you mean when you say "The brain is a computer"? And what is your evidence that this is so?
The brain is an information processing engine. A computer. As I said earlier, it's a packet-switched pulse-coded chemical-biased network processor.
That's simply what it does. You can trace the activity from sensory nerves firing in the retina through the visual cortex and all over the brain as the response to what you are looking at is processed in various ways. At every step, what is happening is computation.
The brain IS a computer.
Ok.... From a man-on-the-street point of view, when you say "your brain is a computer", the first thing I think of is this: You're saying that my brain and the PC on my desk here are both the same kind of thing, in a way.
Yes, in the broad definition of computers.
My PC is a computer (no one would deny that), and my brain is also a computer (quite a few people would deny that, but this doesn't mean it's not true).
Yep.
Now, when I hear that, I assume that if this is true then the two must be similar functionally or structurally, if they are to belong to the same category of thing.
Functionally, yes. Structurally, not at all. The physical structure of computers is almost infinitely malleable. As long as you can build some sort of switch, and join those switches together, you can build a computer.
You can built it out of brass gears and cams, or from an Erector set, or relays, or vacuum tubes, or tiny channels in glass with liquid running through them, or transistors, or living cells. (All of these have been done, by the way.)
For example, a French press and a Mr. Coffee are both coffee makers.
Structurally, they are not similar at all. One is a cylinder with a metal mesh disc that is pressed down into it. The other is an electronic device that heats water and drips it down through a plastic cup with holes in it. But they both make coffee, so they are functionally identical.
Right.
On the other hand, my house and my office are both buildings.
Functionally, they are different. But they both have a foundation, walls, doors, windows, a roof, wiring, plumbing, and insulation, so they are structurally similar.
Functionally they are similar too - they offer protection from the elements and some degree of privacy and security from other people.
However, when I compare my brain and my PC, both the structural and functional similarities appear tenuous at best.
Structurally, my brain is a mass of constantly re-configuring organic neurons arranged into larger structures such as a medulla, a hippocampus, temporal lobes, and so forth.
Right. The important thing to remember is that neurons are switches. They receive an input, and they send out an output, depending possibly on other internal or external conditions.
My computer is a mass of wires and various electronic components with a mother board and a disc reader and things like that. The components are different, their arrangements are different. They are not structurally equivalent.
Right. But the computing part of your computer is the CPU, which is a network of transistors, which are switches, just as the neurons in your brain are switches. A signal comes in, and the transistor - depending on the conditions - will switch a second signal on or off.
Functionally, they are also quite different. Yes, there's some overlap, but not much. Computers are excellent at doing some things that the brain is ok at, and can do many things the human brain can't, and vice versa. My brain can't perform highly complex math at high speed, print charts and graphs, run simulations of moon missions, or play CDs. My PC can't watch someone demonstrate how to pitch a tent and learn from that how to pitch just about any tent, or engage in casual conversation on novel topics with strangers, or get frightened while watching a scary movie.
Okay, let's run through these.
Your brain is much better at maths than you might think. It's so good that you can analyse visual input and manipulate your limbs to catch a moving ball in an intense gravitational field
in real time.
Computers, in themselves, can't print anything, or play CDs. They use external components to do that, the equivalent of your sensory organs and your limbs and so on.
The computer simulating a moon mission is really just an instance of solving a two-body problem in a gravity field. It's the same as you catching that ball.
Your computer may not be set up to learn how to pitch a tent, but it's certainly set up to learn the difference between spam and real email. It's the same thing, just adapted to a different role.
Your computer does in fact engage in casual conversation with strangers all the time - any time you plug in a USB device or attach something to the network, off they go and chat. And don't even get started on Wifi...
As for getting frightened - make sure your anti-virus is active, and then download a virus. Your computer will jump like it's been goosed. Virtually speaking, of course.
Given all that, what does it actually mean when you say "Your brain is a computer"?
It means
your brain is a computer. Really, truly, they are doing the same things.
The brain is wired as an inference engine; this is why we're useless blobs for the first ten or twelve years of our lives, because were absorbing information from every source and forming, testing, and discarding inferences. Once you've built up a useful set of predictive rules about the world, this behaviour slows down significantly, which is why some things are much easier to learn as a child (language, most notably).
We
deliberately build computers that behave differentlybecause we already have plenty of people and we want something that can think, but is good at thinking in precisely the areas we are bad at it. So we build computers that are as rigorous and deterministic and pre-defined as we can.
Also, having to wait twelve years for your PC to boot would suck.
But brains are still computers, and computers, brains.
We can get to the proof once I understand what exactly you mean by that statement.
I hope that helps.