Path: utzoo!attcan!uunet!munnari.oz.au!csc.anu.oz.au!ada612
From: ada612@csc.anu.oz.au
Newsgroups: comp.ai
Subject: RE: simulating brains
Message-ID: <1990Oct2.221006.3024@csc.anu.oz.au>
Date: 2 Oct 90 12:10:06 GMT
Organization: Computer Services, Australian National University
Lines: 32

Re:  Message-ID: <270367E4.160B@marob.masa.com>
     From: cowan@marob.masa.com (John Cowan)

>>But this seems wrong, because brains can also *grow* while they operate,
>>which is not something that finite state machines can do.  Turing
>>machines on the other hand can grow in the rather limited sense that
>>they amount of tape they have written on can get larger, but brains
>>can add new active computational agents, in the form of synapse connections.
>>This is clearly a more radical form of extensibility (if you're interested
>>in what can be done in real time).
>
>I don't understand the sense of your final parenthesis.  Neglecting it for>
>a moment, the claim that brains are superior to Turing machines because they
>can add "new active computational agents" seems clearly wrong.
>
> <discussion of UTMs which I omit for brevity)

The sense of my final parenthesis is that I find the standard idealizations
of computability theory to be a very dubious framework for thinking
about brains.  Computability theory is about what can be done eventually,
whereas brains have to keep up with the real world, always providing some
sort of output in response to the current input.

Consider for example the following basis, which seems to be fairly widely
accepted, for believing that a computer or robot is sentient:  if it looks
like a brain (at the relevant level of structure) and acts like a brain,
it should be presumed to be/have a mind.  But  `fixed horsepower'
computing devices will neither look nor act like brains.  In Searlespeak,
one might say that their causal powers differ from those of brains in a
non-mystical and functionally relevant way.  So why suspect them of sentience?

  Avery Andrews  (ada612@csc.anu.oz.au)