[From Rick Marken (930119.0800)]
First, a correction on the conflict data. The numbers that
measure the fit of model to subject data are not RMS
deviations -- they are % error. So with no conflict , for
example, the error of prediction was about 0.6%.
···
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I'm glad to see the contributions to the "Devil's Bibliography".
Avery -- keep posting candidate entries whenever you find them.
They won't get lost. Greg (as you can probably tell by now) is
an excellent archivist and publisher. Maybe someday the "Devil's
Bibliogrphy" entries will be compiled in an issue (or two) of
Closed Loop.
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Greg Williams (30119) --
Thanks for the excepts from Schmidt. You ask:
There is more, but I'm tired of typing for now. If this is useful, let me
know
and I'll probably post another installment.
Yes. It's EXTREMELY useful. Thank you for doing it and when
your hand and arm return to normal please post some more.
There are some real gems in what you posted already such as:
205 - "The idea is that the system [diagrammed on page 204] can 'compute' the
expected nature of... sensations in the form of a reference and can compare
the feedback it receives on a particular trial with the feedback it expects
to
receive
Sounds right to me; of course, the comparison is part of a continuous process
that makes the feedback sensations match the "expected" (reference)
sensations.
But the statement is consistent with (at least part of) PCT.
After describing how well closed loop models mimic behavior, Schmidt
makes the following, remarkable statement:
The evidence does not prove that humans actually track this way,
but the agreement between theoretical predictions and data is very strong,
and
alternative theories cannot boast of similar success."
So why the apparent eagerness to abandon closed loop models in favor of
other schemes? The following paragraph seems to hold a clue -- it shows that
there is a strong desire to maintain the "information processing" concept of
the
nervous system (stimulus input -->processing-->responseoutput). I believe this
is the result of an unconscious assumption that the "causal model" that
underlies
the information processing view MUST be correct -- closed loop feedback or
not.
This paragraph is a candidate for the frontpiece of the Devil's Bibliography:
211 - "... the information-processing mechanisms, which lie at the very heart
of the closed-loop system shown... [on page 204], require a great deal of
TIME
AND ATTENTION for stimuli to be processed to yield a response.... with rapid
actions sufficient time is not available for the system to (a) generate an
error, (b) detect the error, (c) determine the correction, (d) initiate the
correction, and (e) correct the movement before a rapid movement is
completed.
Muhammad Ali's left jab is a good example. The movement itself is about 40
msec; yet, according to our estimates [made earlier in the book on the basis
of movement-correction experiments], detecting an aiming error and correcting
it during the same response should require about 150 to 200 msec -- the time
necessary to complete the activities of the stages of information
processing.
The idea that this is all part of a continuous LOOP is lost in the dust of the
causal (input-output) view of behavior.
Thanks again for all the work on this Greg.
Regards
Rick