[Martin Taylor 990514 16:12]
Michael Strong apparently 14 May 1999 11:01:02 -0400
(On this list, it is conventional to put name, date, and time headers on
your messages so that replies can be correctly back-referenced--as I have
done for you above).
I am a relatively recent lurker who has been interested in PCT for a few
years now. I have a naive question which I would like to ask this group:
We love such questions, but you may not always get answers on which
everyone agrees:-)
Is there any physiological evidence for PCT? If not, why not? Are there
people examining the nervous system with a PCT paradigm in mind, looking to
see if the circuits are wired as control systems? Do we expect that it
will not be possible to examine the nervous system in this manner for many
decades?
There are two sides to this question. On the one side, Bill Powers has
several times discussed the similarities between the structure and function
of peripheral neural pathways and what one would expect to see if naive
HPCT were correct. The expectation is very like the reality, so far as
we can see.
On the other side, PCT implies _control_, and a control loop is only partly
inside a living organism. The rest of the loop is in the organism's
environment. All organisms live in an environment with the same physical
laws, so one would expect some commonality in the control structures within
organisms. But each species is in a different ecological environment, so
one would expect what looks like a control structure to differ somewhat
across species. And then each individual is in a different social
environment, so each may be expected to be controlling somewhat different
perceptions by different mechanisms at different (and varying) reference
values. So it may not be so easy to identify what is the internal structure
that corresponds to a particular control system in any individual.
Add to that the fact that most structures in living organisms are multi-
functional and distributed, and the mapping becomes a bit problematic
until one can observe the physiological events in individuals organisms
as they control. That's not easy when brain observations must be done
with the head held still in a monstrous machine!
It seems to me as though physiological evidence of PCT should exist in
some sense, and if we could discover it (or its absence), then a lot of
the S/R vs. PCT debates would simply become irrelevant. Because of the
nature of the debates here, I assume that there is some reason why it is
impossible to search for physiological evidence of PCT. Am I missing
something?
Perhaps.
Another point: each of the components of a control loop IS an S-R mechanism.
The output of a perceptual input function depends on its input (and on its
history of input and output variation). That's S-R. Where S-R stops being
appropriate is when the organism is behaving--when the control loops are
completed and actions are allowed to affect perceptions. It's the
functioning organism that is a control hierarchy, not the bits of the
organism that specialists tend to study.
So, it's not _impossible_ to search for physiological evidence of PCT, but
it's difficult when you get away from those controlled perceptions that
don't depend strongly on the commonality of physical law. For the ones
that do depend on physical laws like gravity or thermal diffusion you
may be able to infer the environmental feedback mechanism involved in a
particular control loop, even when the entity you are studying is dead or
immobilised. For most perceptions, though, the researcher would have to be
actively performing "the Test" on the subject while observing the
physiology. And that's perhaps beyond our current abilities in most cases.
Martin