[From Rick Marken (980729.0730)]
Bruce Abbott (980728.2020 EST)
Been there, done that. The signal must precede the shock, by at
least 2 seconds. Five seconds appears to be about optimal. Are
you now ready to grant that I've been conducting the Test with
these studies? (:->
Bill Powers (980729.0429 MDT) already gave an excellent reply to
this post. I'll just try to explain quickly why Bruce's
experiments are not a Test for the Controlled Variable. The reason
is that the subjects in his experiments clearly were not in
control of the purported controlled variable. If the variable
that is presumed to be under control is "signal 5 sec before shock"
then the subject would protect that variable from _all_ disturbances,
including (as I noted) removal of shock. In fact, the subject does
not protect this variable from shock removal, which shows that
"signal 5 sec before shock" is not under control. Another
indication that "signal 5 sec before shock" is not under control
is (as Bill Powers (980729.0429 MDT) notes) the fact that behavior
(press rate) is maximum (rather than minimum, as would be expected,
if error were zero) when the controlled variable is presumably at
its reference ("signal 5 sec before shock").
I think what we are probably seeing in Bruce's experiments is a
rat trying, unsuccessfully, to control the perceived effects of
shock. A signal prior to the shock apprently let's the rat do
_something_ that reduces the perceived effects of the shock
somewhat (assuming that the rat is controlling for zero perceived
effect of the shock). What Bruce is doing to the rats is equivalent
to infusing acid into your stomach at random times then offering
you the option of pressing to get a tiny fragment of Pepto
Bisbol before each infusion or not. I think you would quickly learn
to control for getting the tiny Pepto prior to acid infusion,
not because you are controlling for "Pepto 5 sec before acid" but
because the perception of stomach pain you get in this condition
is a little less horrible than the perception you get in the "no
Pepto" or "Pepto 1 secong after the acid" condition. The only
perception being controlled (unsuccessfully) is stomach pain
but (because the experimenter is unaware of this) it seems like
a sequence ("Pepto 5 sec before acid") is being controlled. I think
this is what is happening in Bruce's experiments. The rat is doing
what it can (in the signal time before the shock) to (unsuccessfully)
control the pain of shock. The experimenter makes it impossible for
the rat to control this perception; all the rat can do is move the
perception of shock _slightly_ in the desired direction (toward, but
not very far toward, zero).
A very important aspect of the Test is to allow the subject
to control the hypothetical controlled variable. That means, the
subject has to be able to bring that variable to _any_ value
he might want. This is why it's important to apply disturbances
carefully when doing the Test; overwhelming disturbances can make
it look like a variable is not controlled when it is or make
it look like some variable is controlled when it is not. The
latter seems to be what happened in Bruce's experiments. In his
experiment the rat is not able to _control_ the relationship
between signal and shock; the rat cannot, for example, act to
restore the shock if shock is removed. So it _looks like_ shock
is part of the variable the rat is _controlling_.
The reason why Bruce was unable to conduct the Test properly
when he did his "preference" experiments was because he didn't
understand, at that time, the nature of control. The Test is
a test to determine whather or not a variable is _under control_.
If Bruce had understood the nature of control at the time, he
could have quickly ruled out "signal 5 sec before shock" as a
controlled variable; rats will not act to protect this variable
from certain disturbances (like shock removal). What Bruce's
experiments do suggest is that rats will do what they can to
_try_ to control the one variable we know rats _do_ control;
perceived effects of shock.
Best
Rick
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Richard S. Marken Phone or Fax: 310 474-0313
Life Learning Associates e-mail: rmarken@earthlink.net
http://home.earthlink.net/~rmarken