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Posted-Date: Thu, 27 Aug 92 09:59:50 PDT
Newsgroups: bit.listserv.csg-l
Date:         Thu, 27 Aug 1992 09:59:50 PDT
From:         marken@AERO.ORG
Subject:      Misc Replies

[From Rick Marken (920827.1000)

Martin Taylor (920826 14:45)

I said:

>OK. There's the trivail truth.

Martin said:

>Even when you acknowledge the
>fundamental truth, its consequences and power are far from self-evident.

For sure. But Martin, you never answered my question; namely, what is the
deeper (non-trivial) truth revealed by dynamic analysis?? I really don't
understand what you mean.  I know that control systems are dynamic and
that these dynamics are important to consider when analyzing and building
control systems.  But can you give me a concrete example of what you
mean by a non-trivial truth. I kinda think it's non-trivial to realize that
1) behavior is just an observable side-effect of an organism's efforts control
various aspects of its own sensory experience relative to internally specified
reference levels and that 2) this means that the only way to understand
behavior (non-superficially and non-statistically) is to try to learn what
sensory variables the organism is controlling.  These two trivial little
truths imply a hell of a big research program. What truths did you have in
mind? Concrete examples would help.

Martin says:

>I'm afraid I don't see the paradox.  What is the problem with controlled
>agents themselves controlling others?

Bill answered this for me.  I will just add one little thing. There is,
indeed, really no paradox involved, though it sounds like there is one when
it is stated as I stated it above (how do controlled agents control?). The
fact of the matter is that agents that control cannot be controlled -- and
efforts to control controlling agents are simply examples of conflict
between control systems.

Avery says:

>Moving on to a more specific point, Bill's arm demo (the version I
>have at least) has to assume that the visual system can track the
>fingertip & the target, whereas a major aspect of Sonja is an
>visual system that can to some extent actually do this (though he ducks
>problems of early vision).

I don't understand this. The arm demo's visual system does track the
fingertip and target, doesn't it? What does Sonja do about target tracking?

Bill Powers says:

>Avery, you are becoming the voice of reason on this net. Keep it up.
>You will get us back on track.

Not if I can help it!  (Just some unreasonable sarcasm).
You are a remarkably temperate and reasonable control system, Avery,
just like your Aunt Mary.

Bill to Martin RE: degrees of freedom.

>I think we will all continue to be frustrated on this subject until we
>come up with experiments that demonstrate this "absolute need."

Ah, the same unreasonable suggestion that I made.

Bill to Ed:

>I put it to you that PCT and HPCT transcend political points of view, as
>well as many others. Except for Rick. Yukayukayuk.

It's true, folks. I AM LEVEL 11.

Martin Taylor (920827 0020) answers Bill's suggestion that experiments
are needed to demonstrate the need for revision of the model based on
degrees of freedom considerations:

>I doubt you could ever find a phenomenon that can be described by only
>one organization.

True. But a collection of observations can usually only be explained just one
of the models.  All I'm asking for is some data that would motivate the need
to revise the existing model (which handles many simple cases of control). I
would suggest a very simple experiment; just so I could get the idea of what
you are talking about. tI scould probably just be a simple extension of a
multidimensional tracking task (which we know the model can handle). Just
create a simple change in the experiment that produces consistent results that
pose a problem for the existing model.

>There really isn't any experimental demonstration that I can think of,
>because

If you really can't do an experiment that tests your proposed revision of the
model then I can't see that it's such an important revision; since the model
accounts for the phenomena we've observed so far I can't see revising the
model to help it explain a phenomenon that we will never be able to
observe.

Hasta luego

Rick


     **************************************************************

Richard S. Marken                   USMail: 10459 Holman Ave
The Aerospace Corporation                   Los Angeles, CA 90024
E-mail: marken@aero.org
(310) 336-6214 (day)
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