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Date:         Mon, 12 Oct 1992 15:53:23 -0600
From:         "William T. Powers" <POWERS_W%FLC@VAXF.COLORADO.EDU>
Subject:      Review comments

Hello, Martin,

I think you should reread the part of your review in which you
referred to the Nyquist criterion (with which I am quite familiar). We
reported that we sampled the data 30 times per second. You said that
this was impossible. In other words, you said we could not have
sampled the data 30 times per second. Therefore we must have been
lying. That is what we objected to. Our experiment iterated 30 times
per second, sampling handle position and recomputing cursor position
on every iteration. This was considerably faster than the Nyquist
criterion would suggest for the traditional 2.5 Hz bandwidth of manual
tracking, but was necessary to show enough detail to detect all errors
between the real person and the model's behavior. A nominal bandwidth
of 2.5 Hz in tracking performance does not include all rapid
variations that are actually produced by human subjects.
---------------------------
You seem to have decided sometime lately that S-R experiments are just
control experiments with the loop broken. This is not at all the
relationship I see between an S-R experiment and a parallel control
experiment.

S-R psychology arose from the observation that when certain events
impinge on organisms, the organisms seem to respond to the events. In
an intact control system, with the loop closed, there is an exactly
parallel phenomenon: when a disturbance occurs, its effects on a
controlled variable result in a change in action that cancels the
effects.

So far you seem to be thinking of a disturbance as a controlled
variable that is arbitrarily altered. You asked me, in fact, what
difference loose or tight coupling of the disturbing variable to the
controlled variable made; this shows me that you don't yet get the
point. Loose coupling is required in order to allow the disturbing
variable to change by an easily-observable amount, while the control
system prevents the controlled variable from changing significantly.
The disturbing variable is a physical variable different from the
controlled variable. It is linked to the controlled variable in some
way that has "give" in it. Thus for a very high-gain control system,
it is possible for the disturbing variable to change over a wide range
while the controlled variable's changes are too small to measure. At
the same time, the output will change over a range comparable to that
of the disturbing variable, opposing its effects. If one actually
seized the controlled variable and tried to make it change by any
significant amount, the output of the system would immediately slam up
against the stops. Even in an ordinary behavioral control system with
a gain on the order of 30, very small changes in the controlled
variable (3 percent of the maximum value of the perceptual signal)
result in full-scale changes in the action that controls it. Actually
breaking the control loop would give you a system that is
hypersensitive to the smallest changes in "stimulation." This is not
what is observed in S-R experiments.

I believe that the correct interpretation of most S-R experiments is
that they are manipulating disturbing variables that are only loosely
linked to the actual controlled variables. The controlled variables,
because they are kept by the "response" from changing, are discarded
by the standard statistical analysis; they do not correlate with
either the action or the disturbance. The disturbance and the response
do correlate because the response is opposing the effect of the
disturbance on the controlled variable. Of course, not knowing that
there is a controlled variable, the S-R experimenter does not pick a
measure of either the disturbance or the response that is appropriate
to the common effect on the controlled variable; the correlations
actually found are far lower than they would be if the correct
measures were used. This loss of precision is exacerbated by the fact
that not knowing of the controlled variable, the experimenter can't
protect that variable from other disturbances that will also produce
opposing changes in action.

So standard "scientific method" is perfectly designed to discard
controlled variables, and to select as independent variables remote
disturbances that have effects on controlled variables -- or would
have effects if it were not for the response. S-R experiments actually
explore the relationship between disturbances that are loosely coupled
to controlled variables and the actions that prevent the controlled
variables from being disturbed. The disturbing variable is interpreted
as a "stimulus," and it is assumed that the organism is sensing it
directly. So it appears that a stimulus is causing a response. This is
what I have referred to as the "behavioral illusion."
----------------------------------------------------------------
In my conversation with you I said that our target audience consisted
of psychologists who were sufficiently dissatisfied with their science
to be looking for a new approach. I did not say that it consisted of
people "naive with respect to psychology but who
might happen to read that journal." You are distorting my words to
make your position look more reasonable.
--------------------------------------------------------------
Bill.
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU