Back in the USSA, Control:Structure and Function

[From Rick Marken (960601.0600)]

We're back from Italy. We had a great time. If you want to hear about
the trip you'll have to come to the CSG meeting where I'll give a talk
on "Degrees of freedom in Italian tourism".

I would like to thank Ed Ford for sending me a copy of William Glasser's
wonderful imitation of a megalomaniac. I would also like to thank Bill Powers
for showing how important it is to have me around on CSGNet -- without me,
even nice guys like Bill P. seem like contentious bastards. I would also
like to thank everyone on CSGNet for keeping things quiet while I was gone
so that I didn't have to wade through a ton of mail upon my return.

Well, back to the fray.

Brian D'Augostino (960531.1022?) --

Bruce, you seem to be saying that the control systems model does
_not_ require the assumption of actual control system components at
the level of physiology. This is news to me.

Bruce Abbott (960531.13:00 EST)]

If control systems exist in a living organism, the physiological components
must be there (of course!)... But there are many physical arrangements that
will produce the same _functional_ unit.

I agree; many different physiological components could implement the same
control function. If the control system components are hormones and you are
looking for neurons, you won't find the physiological components of control.
But if (like Booth, et al) you then conclude that there is no control system
(because there are no components that make up such a system), you are making
an error that betrays just how clueless you were about the nature of control
in the first place. It seems to me that Booth et al could come to this
conclusion (no components = no control system) only if they thought of control
as a structural rather than as a functional phenomenon.

It sounds to me like Booth et al think of "control" as a word that refers to
a particular structure of components; the structure _is_ the phenomenon, from
their point of view. So when no evidence of control structure was found, the
conclusion was that there is no control system.

Booth et al came to this ridiculous (from a PCT point of view) conclusion
because they (like everyone else) missed the fact that control is a functional
phenomenon, viz., the maintenance of a variable (like body weight) in a
reference state, protected from the effects of disturbance. This phenomenon
can be observed (if you know how to do it -- using The Test) so that there is
no question when it is occurring (Bruce Abbott is now in the process of
showing, for the first time in history as far as I know, that rats really
do _control_ their body weight [or a variable related to body weight],
precisely protecting it from disturbance).

PCT does suggest certain physiological structures that might underlie various
examples of control. But failure to find these structures would not rule out
control theory as a model of the functional phenomena of control. Once you
know control is occurring, then you know that there must be a control system
responsible for it. I suspect that physiologists will have a lot more success
in their search for the physiological (structural) basis of control once they
understand the nature of the (functional) phenomenon of control itself.