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Posted-Date: Mon, 31 Aug 92 11:07:24 PDT
Newsgroups: bit.listserv.csg-l
Date:         Mon, 31 Aug 1992 11:07:24 PDT
From:         marken@AERO.ORG
Subject:      Marken Computer Demos/Control

[From Rick Marken (920831.1100)]

I've been off the net for the weekend. Amazing how much
work one can get done when you don't try to respond
to every disturbance created by net postings.

Just a couple quick comments:

Gary Cziko (920828.2237)

>Rick, some time ago you mentioned the possibility of "packaging" your
>programs into one with a menu interface.  I would find this very useful for
>my students.

Well, then I will make it a shorter term goal to do this. It probably
would fit in with whatever I do for Dennis.

Hans Blom (920831) --

>Some general  remarks first. One:  control is not  everything.

Right. "The test for the controlled variable" is how you determine whether
or not control is involved in any observed behavior.

> Two:  what do  we  mean by 'control'?

Production of consistent results in the face of disturbnce.

> Three: where  does control come from?

Control systems.

>How does it originate?

God.

Actually, I don't understand what you mean.

>Four: when you are  explicit and build models,  the
>type of control  that you use seems  to be just the  old-fashioned type
>PID-control.

We build models to accurately mimic behavior, not to keep up with scientific
or engineering trends -- although we like to keep abreast of the latest
technologies since they might make it possible to improve our models (in
terms of their ability to mimic behavior).

By the way. Your description of your e. coli model was somewhat puzzling.
When, for example, does your e. coli model change to a new direction?
What is the criterion for change? In our models, a "counter" is set
after each tumble. The rate at which it counts down depends on the currently
experienced gradient of attractant. The model works beautifully and it does,
unquestionably, control it's perception of gradient. See my paper (with
Powers) in my "Mind Readings" book (it's the one on Random -walk Chemotaxis).

>When you  only have a hammer, you  see nails everywhere. I  do not want
>to detract from  the value of control  theory (a hammer is,  after all,
>sometimes a very useful  instrument), but when you have  control theory
>_only_, you see  control systems  everywhere.

That would be true if we did not have a formal criterion for determining
whether or not we are dealing with a nail. "The test" is that crierion.
The fact is, what people call "behaviors" are consistently produced results
of the actions of organisms -- it is this consistency that makes it possible
to name these results -- "drinking", "driving", "speaking", "walking", etc.
Each of these words describes experiences in which some variable is brought to
some predetermined state and maintained in that state against disturbance.
That is, these are words that describe controlled variables -- the position of
the drinking glass, the position of the car relative to it's lane, the
grammatical order of the words in a sentence, the direction of one's body as
the legs are moved. The variables controlled are not always obvious (because
they are perceptual variables) but the fact that a consistent result is
produced in the context of variable disturbances (and that variable actions are
used to produce this consistency) suggests that SOME variable is being
controlled.

> 'Control'  is an  elusive thing, just  like 'temperature'.

I don't understand this. I can demonstrate control as easily as I can
measure temperature. What's the problem?

> Control 'exists' because we want it to exist

No. It exists because that is the way systems work that exist in a
closed negative feedback loop; control happens.


> Most   emphatically,
>evolution has no  goal; it just looks  that way to the  naive observer.

Evolution may have no goal, but organisms (which evolve) most emphatically
do have goals -- which is the reason why they evolve.

>If there is no goal, 'control' may be as naive a concept.

If there is no goal, then there is NO control.
But organisms have goals (lots of them). They are goals regarding what
they should PERCEIVE and these goals can be revealed using the test
for the controlled variable.

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)
(310) 474-0313 (evening)
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