[From Bruce Abbott (950509.1240 EST)]
Rick Marken (950508.1330)]
Bruce Abbott (950508.1110 EST) --
What Rick seems eager to do with Hans' model is to dismiss it out of hand as
inferior to an ordinary control system,
I "dismissed" Hans' model "out of hand" with Bill's disturbance analysis "in
hand". The disturbance analysis shows that Hans' model doesn't control; that
doesn't mean that Hans' model is an "inferior" control system; it means
that it's not a control system _at all_; it doesn't control.
But Rick, that's exactly my point. Hans' system is not DESIGNED to control
in the PCT sense of the word [I keep saying that last phrase because control
systems engineers use the word "control" less restrictively and I want to
remind you that the name "model-based control" may not be intended to convey
control as here defined]. But it does illustrate an interesting principle,
and I'm suggesting we examine that principle with an open mind.
but every so often we get theories (like model-based
control) that purport to explain control and don't. So we have to deal with
these theories to.
And what I'm trying to get you to understand is that model-based control is
not an alternative theory of control; it's just a technique that might
provide some insight into how people manage to maintain control following
loss of signal, under some conditions, at least for brief periods.
I think you might become a lot less tolerant of various "alternatives" to
what you call the "PCT model" if you would just take off your theoretical hat
for a while and pay attention to the _fact_ that organisms control.
I LIKE wearing my theoretical hat; I think I look rather devilish in it...
And I'm not looking for "alternatives" to control; I'm examining ways in
which control might be implemented. You know, there's more to control than
a closed loop. For example, when you "run in imagination mode," where do
the imaginary inputs come from? If I ask that question, am I looking for an
"alternative" to PCT?
A good way to start looking at behavior as a control process is by putting
those rats you've got into some experiments where you can see their
controlling up close and personal.
An even better way is to construct tracking programs, serve as participant,
and construct PCT models of your performance on these tasks. But I am still
planning to get the rat studies done; I should have the time to get set up
now that I'm on "vacation" (I use that term lightly; for me vacation means
no having to trudge off to class every few hours, and no paycheck).
Perhaps I should just say that
the number of people who are (or have) done (and published) PCT research is
depressingly small.
Question: What do you DEFINE as PCT research? That is, to qualify as PCT
research, what elements must be present? I'd like to be able to examine,
say, a piece of published research and using your criteria, classify it as
PCT or non-PCT. [I have some thoughts on this, but I'd like to hear yours
first.]
Regards,
Bruce