[From Bill Powers (980224.0158MST)]
Bruce Abbott (980223.2005 EST)--
(writing to Rick)
I assume that you write this for the general audience and not me in
particular, as I do understand this. But let me test _your_ understanding.
Assume that you had an ideal control system of the type we usually diagram
-- one that continuously and perfectly countered all disturbances to the
controlled variable (except for the constant residual error needed to
maintain output against a constant disturbance). The correlation between d
and the cv is 0.0. Yet the correlation between d and o is 1.0. How is o
able to vary perfectly with d if d is uncorrelated with e, through which the
influence of d must pass?
There are two issues here, of which the less important is Rick's
idealization of the control equations. The more important one is that we do
find, experimentally, that the correlation between d and o is close to -1,
while the correlation between d and cv, or between cv and o, is usually 0.2
or less (disregarding sign). Just run the demos in Demo 1, many of which
actually compute these numbers from a short run that the user does.
If you think of d affecting cv, cv affecting e, and e affecting o, it is
impossible for the correlation between d and o to be greater than any of
the intervening correlations. Yet that is what we see, reproducibly and
even with a randomly-selected participant. The fact that we see this
"impossible" relationship among correlations is what proves that the lineal
model can't be correct. It is not correct because the causation is not
lineal; feedback is involved.
If you model a control system with an integrating output, you can find high
correlations between d and cv, and between cv and o. This is because in the
computer model there is no noise. If you add a small amount of noise
anywhere in the loop (for example, in the error signal), you will find that
the intermediate correlations drop sharply, while the overall correlation
between d and o remains high (and negative). The system is now keeping the
error signal small, but the noise is comparable to the error signal, so
this destroys the intermediate correlations. This is what is happening with
the real experiments; the noise in the human control system is about the
same as the minimum error that the person can maintain.
This changes your question from rhetorical to a literal request for
information:
How is o able to vary perfectly with d if d is uncorrelated with e,
through >which the influence of d must pass?
Stated more realistically, the question is, "How can the correlation of d
with the cv and e be lower than the correlation between d and o, when the
influence of d on o must pass through the cv and e?" Since this is what we
actually observe, the question presumably has an answer that doesn't rely
on magic. And it does. The answer is control theory.
Where I've fought at all, it has been
against assertions said to be based on PCT which I find do not follow from
PCT at all. (One of them is the assertion that the behavioral illusion
destroys the foundations of "conventional" psychology, but I don't want to
open THAT can of worms again.).
The behavioral illusion reveals a relationship among correlations that is
impossible under the conventional input-output interpretations of behavior.
Not only does it show this correlational paradox, but it shows that the
apparent relationship between a stimulus and a response, conventionally
defined, may have nothing to do with the actual relationship mediated by
the organism. I don't think you have really understood either of these
points. Your lack of understanding of the correlational paradox is shown by
your rhetorical question above, and your lack of understanding of the
second point is shown by your claim of an exemption for stimuli you have
used, not realizing that a mere response to a stimulus does not prove that
the stimulus is actually what is being sensed. If you had understood the
second point, your objection would have taken a different form: you would
have shown that all disturbances tending to alter the stimulus would be
counteracted by corresponding changes in the system's action. The
indications are that you still believe there are some stimuli that cause
behavior directly, through an open-loop sensory-motor link.
Just to be as explicit as possible: PCT is based on the idea that _ALL_
behavior is produced as a means of controlling some perceptual variable.
This means that there are NO stimuli that produce behavior in an open-loop
way -- and that includes "responses" to puffs of air on the eyeball and
pinpricks and loud bangs behind the head. In all cases where such
"responses" appear to happen, there is really some controlled variable that
is affected one way by the apparent stimulus, and the opposite way by the
supposed "response." The apparent stimulus is only a physical disturbance
of some controlled variable, and the apparent response is an attempt by a
control system to resist the effects of the disturbance. If the disturbance
is applied slowly enough for control to succeed, it will be clear that the
so-called response actually prevents the disturbance from having any
significant effect on the organism.
The behavioral illusion creates a _highly convincing_ illusion of direct
cause and effect. For example, if you apply a shock to a rat, doesn't it
seem that what the rat does is truly caused by the shock? But a PCT
analysis would say that the shock merely disturbs a controlled variable
(more likely, a whole lot of them) and that whatever part of the reaction
is not caused by the shock itself acting directly on muscles is an attempt
by one or more control systems to restore their controlled variables to
their preferred conditions. The shock itself is obviously not a controlled
variable; there are no specialized sensors for electricity. The shock acts
on sensory nerve-endings that normally detect such things as temperature,
pressure, vibration, pain, position, and so on; the control systems
involved exist to maintain these variables, not electric currents per se,
at particular reference levels. The reaction is not a reaction to
electricity; it is an attempt to restore the disturbed variables to their
reference states.
So the use of shocks as a stimulus, as in some experiments you have done,
is a clear invitation to be fooled by the behavioral illusion. When you
said that in YOUR experiments this illusion was irrelevant, I wondered
whether you were thinking of the shocks. In fact, your statement made me
wonder if you even understood how the behavioral illusion works. Unless you
have proven, by using the Test, that a specific stimulus is in fact being
controlled by variations in an organism's actions, NO stimulus can be
automatically exempt from the suspicion that the behavioral illusion is
involved. Any stimulus that can be freely varied without direct opposition
by the organism is by definition a disturbing variable, not a controlled
variable or controlled perception.
Best,
Bill P.