camps, Reviews

[From Rick Marken (930124.1000)]

Avery.Andrews (920123.1050)

I quoted from Ford & Ford:

>"Human sensori-perceptual capabilities are designed to collect information
>useful for GUIDING PRACTICAL ACTION in the physically structured and
>dynamically varying terrestrial environment in which humans evolved"
>p 22 emphasis mine

Avery says:

Hmm. This sounds fine to me, at least if `are designed to collect' is
replaced by `have been selected for success in collecting'.

It was the part about the perceptions guiding action that I found
objectionable. In a control loop, it is more appropriate to say that
action guides perception while compensating for any disturbances to the
intended state of the perception. If anything is "guiding practical
action" in a control loop, it is the net effect of the disturbance on
the controlled perceptual variable. Ford and Ford's little error in
phrasing is very common in commentaries on PCT; it is a reflection of
the "behavioral illusion" -- the idea that input (whether you call it
informaiton, feedback, stimulation, invariants or whatever) guides
output (which is usually called "behavior"). I would argue
that this phrase could be considered a litmus test of one's
understanding of PCT. Anyone who says that output is guided by, a result of,
or planned on the basis of input unquestionably does not understand
how a living control system works. This is NOT a matter of stupidity,
by the way. This is a VERY hard thing to understand;and harder to believe,
even after you have seen it demonstrated. Many PCT demos are designed
to illustrate just this point -- that input is NOT the cause of output in
a closed negative feedback loop.

Gary Cziko (930123.1655 GMT)

Rick, why did you pick Chris Wickens? Is it because perhaps I've mentioned
him on the net (he's the advisor of a graduate student who is my next-door
neighbor), or is he really well known in human factors? If the latter,
what do you know of him and his work.

I didn't remember your mention of Wickens. I know of him because he
does a LOT of publishing in the journal Human Factors (he is on the
editorial board), he has written chapters in some of the major "compendia"
of Human Factors "wisdom"; he wrote a chapter on manual control for an
important collection of "basic psychological facts" for Human Factors
engineers. I've never met him but he is highly visible to me from his
very active publication activity. I believe he would be considered one
of the current gurus of manual control. He seems to know the mathematics
of control theory quite thoroughly and he knows all the control engineering
tools for studying control systems (Laplace transforms, Bode plots,
etc etc). So he would probably be able to give a very intimidating
review of our control research -- just what we need, I think. He'll
tell us why psychologists already know all this (PCT) and more; our
challenge will be to politely explain that they have missed the most
important point -- that control systems control their own perceptual
input relative to secularly adjustable reference levels. I would bet
dollars to donuts that he won't get it -- but, like William F. Buckley
(who remains clueless about nearly everything except drug policy) he
will at least be a capable opponent.



[Avery Andrews 920125.1529]

(Rick Marken (930124.1000)

> If anything is "guiding practical
>action" in a control loop, it is the net effect of the disturbance on
>the controlled perceptual variable.

Well, that's pretty much what I interpreted them as saying, but you
actually say it, rather than just allowing me to read you that way.
The vagueness and ambiguity of a lot of this literature is certainly
a major problem with it, which deserves a lot of attention.

Another likely devil's bib entry is:

  Adams, J.A. (1971) `A Closed Loop Theory of Motor Control', Journal
   of Motor Behavior 3:111-149.

A survey of recent theories of motor behavior that I've been looking at,
and may report on shortly, cites this as the origin of the (supposedly
defunct) `closed loop' paradigm.