Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!columbia!caip!ll-xn!cit-vax!elroy!smeagol!usc-oberon!sdcrdcf!psivax!friesen
From: friesen@psivax.UUCP (Stanley Friesen)
Newsgroups: net.physics,talk.philosophy.misc
Subject: Re: Quantum free will
Message-ID: <1433@psivax.UUCP>
Date: Thu, 11-Sep-86 16:03:58 EDT
Article-I.D.: psivax.1433
Posted: Thu Sep 11 16:03:58 1986
Date-Received: Fri, 12-Sep-86 22:23:26 EDT
References: <179@sri-arpa.ARPA> <123@omepd> <129@omepd> <15600@ucbvax.BERKELEY.EDU>
Reply-To: friesen@psivax.UUCP (Stanley Friesen)
Organization: Pacesetter Systems Inc., Sylmar, CA
Lines: 64
Xref: mnetor net.physics:2951 talk.philosophy.misc:12

In article <15600@ucbvax.BERKELEY.EDU> (David desJardins) writes:
 
>   *Everything* exhibits QM indeterminacy.  For a neuron, I am sure that
>if you measure the exact instant that it fires (say, as determined by the
>point at which its output first exceeds a threshold value), you will find
>that the fifteenth significant digit is as random as you could want.

	Quite probably, but I doubt this is of any biological
significance(for more detail, see below).

>   The same is true of a TTL chip -- if you measure the fifteenth significant
>digit of its output voltage, you will find it to be completely random.  The
>difference -- or at least a possible difference -- is that digital circuits
>are designed to correct for small random fluctuations; the output of a TTL
>chip is virtually uncorrelated with the fifteenth significant digit of its
>input.  I have seen no evidence as to whether this is true of human neurons,
>or whether they can tend to amplify these small fluctuations.

	Just because the brain does not use exactly the same methods
as electric circuits in smoothing out minor fluctuatiations does not
mean that it doesn't do so. In fact it has several different
mechanisms, operating at different levels, which tend to damp random
fluctuation, except where it is useful. First is something very like
what curcuits use, a threshhold system. Discharge of a neuron is
triggered by an incoming signal which exceds a certain threshhold. In
most cases this lower limit is considerably larger than the signal
generated by a single input neuron. Second, the coding used by the
nervous system is such that a single discharge has little or no
meaning, it is the *rate* of discharge that is meaningful. Small
scale variations in the timing of an individual spike simply have no
effect on the averaged rate of discharge of a spike train. Third, the
nervous system is highly parallel, with considerable overlap between
adjacent data streams. Thus most significant results are based on a
consensus of several semi-independent "computations", much like the
use of triple redundency in "reliable" computer systems. So the brain
in fact has considerable means of suppressing unwanted randomness.

>   And, in particular, since we don't know how the neurons are organized,
>we don't know how subsequent neurons will be affected by random fluctuations
>in their inputs.

	You would be suprised at how much we *do* know about how
neurons are organized, at least in certain parts of the brain such as
the Cerebellum, the Visual Cortex, and the Sensori-Motor Cortex. One
of the main research problems now is the *intermediate* level of
organisation, between the large scale organization of the
neuro-anatomist and the small scale organization of the local
processing complex.

>   As has been noted, carrying information is different from computational
>power.  A machine with a RNG is in certain ways more powerful than one
>without.  It is certainly a better poker player!

	Here I agree with you, the brain needs, and almost certainly
has, a randomness generator, perhaps more than one. I rather doubt
this takes the form of a random *number* generator though. Of course
any randomness generator can be constructed from a RNG, so this is not
a computationally significant point.
---

				Sarima (Stanley Friesen)

UUCP: {ttidca|ihnp4|sdcrdcf|quad1|nrcvax|bellcore|logico}!psivax!friesen
ARPA: ??