X-Message-Number: 15017 Date: Fri, 24 Nov 2000 22:55:30 -0700 From: Mike Perry <> Subject: Brains and Turing Machines Once Again Thomas Donaldson, #14997, says: >So far the only person on Cryonet who has come close to answering my >question about whether or not humans may be considered Turing machines >is Mike Perry. His references to computer material, however, need much >more in that they do not really discuss candidates for Turing machines >like human beings. It seems to simply be assumed that thinking requires >a Turing machine. Maybe so, maybe not, but an explicit demonstration >WHICH uses the features of brains which I have explained in previous >messages would prove useful, one way or another. Does all thinking >map easily into a Turing machine? Does it map at all? Thomas, the whole approach I have taken with this is a brute-force one of just going directly to the quantum level, where you are just looking at state changes, albeit very many of them. Clearly, based on accepted physics, you can calculate these changes for any specified, finite system, thus for the human brain, thus you can model the human brain with a Turing machine. You don't need to worry at all about the higher functions, symbolic vs. non-symbolic processing, neurons that grow new connections, etc. All these are emergent, high-level features that are implicit in the lower-level phenomena you are actually dealing with. "Candidates for Turing machines": take a universal Turing machine, then choose an appropriate description of a brain, and go for it. Of course, then you must ask just what to include in your description. And the answer is: I don't know, and I don't see how anyone else could either, at our present state of knowledge. All I would confidently assert is that there *exists* a suitable description ("exists" in the mathematical sense, not in the sense of it having been realized). At least this follows if we can trust quantum mechanics, as seems to be the case though as usual it is not guaranteed. But if so, then we can conclude that all thinking maps into a Turing machine. Whether easily or not is another matter, and again I don't know the answer, other than to say that the brute-force approach would not be an easy one. Mike Perry Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=15017