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Date:         Tue, 25 Aug 1992 13:49:16 -0600
From:         "William T. Powers" <POWERS_W%FLC@VAXF.COLORADO.EDU>
Subject:      Hotshots; encoding
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[From Bill Powers (920825.1300)]

Tom Bourbon, Rick Marken (920825) --

Rick: "The question: Why is there such reluctance on the part of those
working on the hot approaches to behavior to even consider the
possibility that behavior is the control of perception?"

Tom: " Do the authors of work about "leaning on the world" address
the nature of how control is achieved under those conditions?"

It pains me, too. All of these people are fumbling around gradually
discovering the facts of control, doggedly going down every blind
alley and backing out again for another try. Chapman or Agre (I forget
which) told me a month or two ago that Pengi is old stuff -- they've
gone on to much bigger things now. So Pengi is a broken toy abandoned
amid the mess of the playroom.

As I said to Rick on the phone a couple of days ago: Agre, Chapman,
Brooks, and all the rest of that genre strike me as young hotshots
cranked up to overload, working at top speed and hoping to get lucky
and hit the bigtime payoff. They're brilliant, impatient, tremendously
competitive, and undisciplined. It's probably hopeless to try to get
them to settle down for a minute and learn something, like how control
systems work. They'd rather figure it out themselves, because
basically they don't think that anyone else could come up with
anything as good as what they produce.

Right now all these people are going through the discovery phases that
every CSGer has gone through, and that I went through starting in
1953. The difference is that they don't seem to want to learn control
theory, so they're working with one hand tied behind their backs.

So what do we do about it? I don't think it's worth a lot of effort.
They're going to resist all the way. If they do discover control
theory on their own, they aren't going to come running to us with the
news. It will be too embarrassing to admit that control theory existed
before they were born, that all the engineers knew about it and could
have told them if they'd just asked. To hell with 'em. There are
plenty of people who want to know about control theory. I've wasted
enough hours and days and weeks trying to make some sense out of the
confused ramblings of dilettantes. Let's just get on with the work.
----------------------------------------------------------------------
Tom, I hope there's something left of Galveston when you get back.
----------------------------------------------------------------------
Martin Taylor (920825) --

Thanks for the added analysis of df. I bow to your superior experience
with this field.

RE: the description of motor neurons encoding for the consequences of
motor action. One of my objections was to the use of terms that don't
mean anything, like "encoding." As far as I know, there's no special
code in a motor output signal. It's just a signal that gets bigger and
smaller. There's nothing about it that says what it's going to be used
for. It just makes a muscle get tight.

To say that "... motor neurons in the monkey cortex encode not the
force being applied by the muscles, but the force needed to counter
the (visual) disturbance ..." makes it sound as if the motor neuron
knows what's going to become of its output signal, or that it would
give some special coding to the signal if it were used to counter
visual distubances instead of just making a muscle get tense. In fact,
a motor neuron signal creates a force, period. What the authors of the
article discovered was that output does not correlate with outcome,
but with disturbances. We already knew that. You can verify that
without looking inside the brain. They did NOT find out how the brain
manages to produce just the right signal to the right motor neuron to
counteract the visual disturbance. They did not, in other words, find
the control system -- only its output function.

>Here we have not only [the CEV being controlled], but an apparent
>window into the control hierarchy itself.  I don't see why that
should >bother you.

That's not what bothers me. What bothers me is the attribution of a
causal property to the motor neuron, an attribution that makes it seem
as if the neuron could know that THIS time its output is being used to
counteract a visual disturbance, instead of for example gravity. I'm
not bothered by neural evidence that control systems really exist. I
expect neural evidence to show that. I'm bothered by the implication
that finding the motor neuron that produces the appropriate force is
enough to explain the result. We know a force has to be produced if a
disturbance is counteracted. We know that a neuron, or set of neurons,
must produce it. What Geogeopolis did was to find the neuron. If he
had gone on to raise the question of what generated the signal drove
that neuron in such a singularly appropriate way, I might have saved
the article.

Maybe I'm just getting burnt out.
----------------------------------------------------------------------
Best,


Bill P.
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU