Newsgroups: bit.listserv.csg-l
Date:         Thu, 27 Aug 1992 00:50:01 EDT
From:         Martin Taylor <mmt@BEN.DCIEM.DND.CA>
Subject: Re: Misunderstandings & miscellany

[Martin Taylor 920827 0020]
(Bill Powers 920826.2000)

Talking about my claim to have demonstrated a novel and important fact about
PCT through consideration of dynamics and the associated degrees of freedom...

> What we need is a demonstration with a
>live human subject in which a phenomenon occurs that can only be
>explained by this organization in a model. It should be something
>simple enough to do on a PC, so that the modelers on the net can do
>the experiments, program the model, and test the match. We can
>stipulate (as Avery pointed out) the existence of perceptual devices
>as required to provide perceptual signals representing whatever
>aspects of the environment are needed.

I doubt you could ever find a phenomenon that can be described by only one
organization.  If you want an anecdotal set of facts that fit the proposed
organization, then you need only look at someone's head turn to face the
source of an unexpected noise, or the flick of the eyes toward a distant
light flash.

The argument goes the other way: if there are more sensory df than motor df
(either instantaneously or over time) and if a system is a living one (i.e.
has been built by Darwinian evolution), and if PCT is valid for living systems,
THEN there must be passive alerting systems that can direct control among
the possible percepts permitted by the sensory systems.

I make no claim for any specific organization of how these alerting systems
might work.  I only claim that different percepts must come under control at
different times, and that there must be some mechanism for shifting control
to those percepts it is most important to control at any particular moment.
The instigator of that change is what I call the alerting system, which might
well not be a separate system from the control hierarchy, but which must work
passively and effectively in parallel across all the percepts that might be
controlled (or at least across those not currently being controlled).  Your
proposed organization might fulfil these criteria.  I don't know.

There really isn't any experimental demonstration that I can think of, because
you can't unbuild an evolved living system, and if you deliberately build a
simulation to have alerting systems that can affect what is controlled, then
you are testing a tautology.  I guess you might set up (or attempt to set up)
a negative demonstration--a system that had far more sensory inputs than
motor outputs, that could control appropriately many percepts at several
levels, and that had no passive parallel alerting system.  Success at such
a demonstration would show that such an alerting system is not necessary,
but I think it would be necessary to provide an equivalent (e.g. an autonomous
scanning system checking on the errors of currently non-controlling ECSs).

This basic condition for any such simulation is that the sensory system of
the simulated controller be much broader-band than the motor system, and that
the environment be rich enough to justify the sensory bandwidth.
What this means is that the experimenter-simulator must set up lots of CEVs
that the simulated organism could learn or be constructed to control (depending
on whether we wanted to bring an experiment on reorganization into this).
It may be that it would be easiest to do this in the natural world.  But
perhaps one could work with a very restricted world, using a 2 df motor
system and, say a 6df sensory system of bandwidth higher than the motor
system by an order of magnitude.  That would give 30 times as many sensory
df per second as motor df per second.  Even this, I think, would be hard
to mate with a simulated world, especially when the objective is to show that
the organism can control a considerable variety of percepts, for each of
which the environment must provide the data, at several justifiable levels.

Maybe more experienced modellers than me could see a way to try such a
negative demonstration.  Maybe someone else can think of a way to do a positive
demo or experiment.  I think of it as a fact on the same level as that you
can't keep a cursor on a moving target unless you can see at least the
deviation of the cursor from the target.

Martin
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