[Avery Andrews 930317.1514]
I can't find my copy of Allan's WTP citation list, so don't know if
the Fowler et. al. paper I mentioned last night is on it, but it does
seem pretty clear that the specific criticism of PCT is just a repeat
of that in Fowlder & Turvey 1978, and that the authors are suffering
from a case of double-standardism, in that the same kind of problem
that sinks PCT-without-reorganization sinks their concept of
`coordinative structure' in exactly the same way, since `coordinative
structures' don't differ in any way I can perceive from higher-level
control systems.
In fact, F,T et al. may have done us a service by producing some
specific examples of useful systems of this kind, since BCP is a bit
sketch on the details. One of their examples is that of an airplane,
where a joystick is connected to ailerons, wing-flaps, & a rudder,
so that moving the stick to the left lifts the left flap, lowers the
right and waggles the rudder to the left, etc., thereby folding three
degrees of freedom into one.
Now if the physical systems aren't mechanically linked, the question
arises of how this `folding' is to be achieved. F&T don't have much
of anything to say about this, but one signal setting multiple reference
levels via an output fan seems the obvious way to do it. Now if these
reference levels are for forces, problems will arise if there is
turbulence, etc., since different opposing forces on the various
airfoils will result in different positions being obtained, with
presumably suboptimal results. So the answer is to have the left-right
`lean' of the joystick set position reference level for the three
movable airfoils, & then we have a nice hierarchical control system
doing something useful.
To finish off the whole person-airplane system, we can say that an error
in heading (angular deviation of nose from target object) determines a reference
level for change-of-heading, which determines a reference level for
joystick position, which determines an assortment of reference levels
for airfoil positions, which determines reference levels for forces
applied airfoils.
Btw, while I certainly agree that Fowler & Turvey get PCT seriously
wrong, I don't think they are particularly heinous by academic standards
- people just aren't expected to work that hard to understand the other
guy's positions. You just gotta put together a reply and politely
straighten them out. It also seems pretty clear to me that F, T & Co
have some kind of serious ideological obstacle to accepting control
theory (Dionysius of Halicarnassus (c. 0 AD) tells us that ignorance will
be right by chance some of the time, but only perversity will be wrong
*all* the time), but that doesn't mean that there's no point in answering their
arguments. People do occasionally change their minds, and then there
are who knows how many uncommitteds wandering around out there.
People just don't care about the input-output model of behavior as
much as Rick thinks they do. Indeed, I suspect that one of the reasons
linguists don't spend much time in the psych lab is that the
input-ouput, IV-DV stuff just seems stupid and boring to them, w.r.t.
the things they are interested in, but that's the only thing that people
seem to know how to do in labs.
Avery.Andrews@anu.edu.au