

Problems With Life Extension: The Brain - edw519
http://www.blank89.net/2008/06/problems-with-life-extension-the-brain/

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dhs
From the article:

    
    
       One of the sacrifices that will have to be made is that we will have to admit that we could be emulated on a computer and are little more than self aware information.
    

I don't have any problem per se with the idea that my brain might be a
computer. However, this idea has been repeated now for more than 50 years,
with very little empirical evidence of the digital modus operandi of brains
_that I know of_. I would appreciate some pointers to recent scientific works
which support the brain = computer hypothesis.

~~~
xlnt
What do you propose a brain might be doing, other than computation?

We have an existing theory that our computers are _universal_ (even a Turing
Machine is), which means they can do any possible computation. If the brain
does computations, then our computers could do the same computations.

~~~
dhs
I know the theory. I'm asking for pointers to experimental evidence that it is
true.

There are competing theories. One of them, which is backed by some empirical
evidence, is "Continuity of Mind" by Michael Spivey

[http://www.amazon.com/Continuity-Mind-Oxford-
Psychology/dp/0...](http://www.amazon.com/Continuity-Mind-Oxford-
Psychology/dp/0195170784)

Short summary by Spivey:

[http://www.cogsci.rpi.edu/CSJarchive/Proceedings/2003/pdfs/3...](http://www.cogsci.rpi.edu/CSJarchive/Proceedings/2003/pdfs/32.pdf)

Another approach, also relying heavily on experiments, is the "Grounded
Cognition" thesis, of which Lawrence Barsalou gives a good summary:

[http://www.psychology.emory.edu/cognition/barsalou/papers/Ba...](http://www.psychology.emory.edu/cognition/barsalou/papers/Barsalou_ARP_2008_grounded_cognition.pdf)

From the abstract:

"Grounded cognition rejects traditional views that cognition is computation on
amodal symbols in a modular system, independent of the brain’s modal systems
for perception, action, and introspection. Instead, grounded cognition
proposes that modal simulations, bodily states, and situated action underlie
cognition."

EDIT: I forgot a very interesting one involving a computational experiment:

Selmer Bringsjord, "A New Gödelian Argument for Hypercomputing Minds Based on
the Busy Beaver Problem"

<http://www.osl.iu.edu/~kyross/pub/new-godelian.pdf>

Now I'm looking for evidence which supports _your_ theory - that brains =
minds = computers. Affirming that a theory exists without providing evidence
that it is true is not enough.

~~~
mojuba
As an example,

 _modal simulations, bodily states, and situated action_

\- which of these are not computation?

~~~
dhs
Yeah, the candidates are not all alike, even though Barsalou cites Spivey, who
is really in the analogue camp. In contrast, the "Grounded Cognition" idea
revolves around simulation - which may or be not work in an analogue manner -,
and only denies the existence of amodal symbols in brains, as opposed to, say,
Jeff Hawkins (who didn't do any experiments, either, AFAIK). Bringsjord is
still another case; he's an Ex-GOFAI guy who, together with David Ferrucci,
built the storytelling system BRUTUS.

<http://www.chass.utoronto.ca/~sousa/BRUTUS_rev.html>

Bringsjord makes another relevant contribution to the debate in "BRUTUS and
the Narrational Case Against Church's Thesis", which used to be available from
citeseer, but that site is down ATM, so I cannot provide a link.

But since you're asking a question of your own instead of answering mine, I
take it that you don't know of any evidence, either.

~~~
xlnt
One cannot present evidence to differentiate between two theories unless they
are both coherent and make clear and different predictions. Arguments against
theories is a valid way to deal with them; so is asking questions to clarify
what they are saying.

~~~
dhs
I don't understand you there. Spivey can make experiments which lead him to
conclude that there may not be any fixed representations of anything in the
brain. Bringsjord can manually solve the Busy Beaver for 6-state Turing
Machines, while the machines themselves can't. These are examples of what I
have; what I'm now looking for are examples of experiments from the results of
which the opposite can be concluded.

~~~
xlnt
How is it relevant whether there are any fixed representations in the brain?
self-modifying code could achieve that.

there is no reason to believe that bringsjord can solve that problem and a
computer can't. divide his method of solving it into very small steps. then
answer which step did he do which a computer can't do?

~~~
dhs
The Busy Beaver is a classic example of a function which is not computable by
a Turing Machine.

~~~
xlnt
You haven't said which step he took to compute it which a turing machine can't
do.

~~~
dhs
There are many steps. You have a set of different Turing Machines with
alphabet {0,1}, each of which has, say, 4 states. You want to know which of
these is the one that, starting from a tape filled with 0's, can write the
largest number of consecutive 1's onto the tape, before it halts. _If_ it
halts - you don't know that in the beginning. A human can find out, by
manually simulating the sequence and counting the steps. It's a lot of work -
there are 61.519 possible 4-state machines -, but Bringsjord (or more likely,
a group of undergrads available to him) has/have done it. A computer can't do
it. For details, please read the paper.

~~~
xlnt
You're telling me that a computer cannot simulate steps of a turing machine,
one at a time? it can't store the current state of the turing machine, and the
rules, in memory, and use the rules to get from one state to the next?

Are you really saying that a computer _with too little memory_ can't do it, or
something like that? because it seems blatantly obvious that a computer can
simulate a turing machine.

~~~
dhs
A Turing Machine _is_ an idealized computer. But no computer/TM can find out
which of the possible 61.519 4-state TMs can write the longest string of 1's
on a blank tape before halting.

~~~
xlnt
A computer can try each TM one by one in the same way the humans did.

If you're talking about the halting problem now, humans also don't know
whether the TM they are manually simulating will halt eventually.

And you still haven't said specifically what the thing is that the humans do
and computers can't.

~~~
dhs
No, a computer cannot do it, due to incompleteness (Once there was a man
called Kurt Gödel...) Bringsjords experiment proves that humans can
"hypercompute" uncomputable functions. The great majority of functions which
exist are uncomputable.

