From: marken@aero.org (Richard Marken)
Newsgroups: bit.listserv.csg-l
Subject: Martin's beliefs -- what for?
Date: 23 Nov 1992 23:47:35 GMT
Organization: The Aerospace Corporation, El Segundo, CA
NNTP-Posting-Host: aerospace.aero.org

Martin Taylor (921123 11:40)

>When I talk about a "belief" as a structured percept, I am taking account of
>the multidiemsionality of the perceptual structure.  Many parallel perceptual
>signals may be components of a "belief," even if there is no actual control
>of the belief as such--no single perceptual input function to which it
>corresponds.

So you use "belief" to refer to a set of parallel perceptual signals,
so b = (p1,p2...pn) -- belief b is a set of perceptual signals p1,p2.
OK so far? There may be no perecptual input function that corresponds to
this belief. I take this to mean that the set (p1,p2..pn) is not 
converted into a new perceptual signal, p, where p = f (p1,p2,,pn).
Ok still? So what is the belief for (in the model) -- what does it
explain? It appears that it might be of interest to an observer of
the brain in which these signals exist as a belief -- but of what use
is it to the brain itself?

>  There is only control of the multiplicity of scalar perceptual
>signals, all of whose related error signals are to be brought near zero.
>It is not necessarily satisfactory for any single function of those signals
>to be brought to a reference value, though it could be satisfactory for
>several orthogonal functions of those signals simultaneously to be brought
>to their several reference values.

Satisfactory?? What is being satisfied?? Satisfactory imples that
something in the system wants the set of signals (the belief) in a certain
state. What does? How does it do it? I really just don't understand what this
concept of "belief" is designed to explain and how it explains it. 

I believe that multidimensional perceptual signals are converted
functionally into scalar perceptual variables because that is the only
way I know how to model a system that controls multidimensional variables.
If you know of another way, then I would be happy to learn it. But to me
it sounds like what you are saying is that there are sets of signals
(beliefs) that are controlled as a whole -- even though they are not
converted into a scaler perceptual variable. I don't see how this works.
I think you are just describing an observable side effect of the way
multidimensional control works. If 10 systems are controlling 10 inputs
you will be able to compute intercorrelations between the variables and
find significant "factors" (because, as you note, of correlations between
disturbances to high order systems that set the references for these
variables). But that is just a side effect of control -- like the fact
that a person might end up writing "Pride and Prejudice" as he 
resists dosturbances to the knot in the rubber band demo. 

But what is it that you think is explained by these "beliefs"?
Just curious. They don't seem to require any changes in the
PCT model since these beliefs are not really part of the model.

Best

Rick


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Richard S. Marken                   USMail: 10459 Holman Ave
The Aerospace Corporation                   Los Angeles, CA 90024
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