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Posted-Date: Thu, 19 Nov 92 10:23:29 PST
Newsgroups: bit.listserv.csg-l
Date:         Thu, 19 Nov 1992 10:23:29 PST
From:         marken@AERO.ORG
Subject:      Re: Complexes of perceptions

[From Rick Marken (9921119.1000)]

In a rush to morning meeting but...

Oded Maler (921119) to Bill P.

>You seem to claim that a signal which is a combination of two
>or more other signals "really" (explicitly) exists when there
>is a "gate" that takes the two wires and outputs on a third wire
>a signal whose observed value is the combination of the two.

>Now consider a different situation where those two signals are
>not combined to create a new perceptual function which is servoed,
>but rather are both servoed independently but their effects
>are combined via the output function (e.g., two nerve fibers that
>feed into neighboring parts of the same muscle).

>In such situation a, there exist virtually a combined signal which
>can behave as-if it is the controlled signal, but it does not really
>exist inside the system. Put it another way, the "real" signals
>can be probed directly (in principle) by an external observer, but
>in order to observe the "virtual" signals, the measurement instruments
>of the observer should also include the missing circuits for creating
>the combinations.

From your description I get

o1 = f(p1) , o2 = f(p2)

o = g(o1 + o2)

p1 = h(o) ; p2 = h (o)

where p1,p2 are perceptual signals, o1 and o2 are their
outputs and o is the muscle output resulting from the
combined effect of o1 and o2.

I think you would find that p1 and p2 (the seperate
perceptual signals) are not independently controllable.

But maybe my representation of your suggestion is wrong?
Could you help me out here, Oded.

It seems that you and Martin and maybe some others
believe that perceptions can be represented in
"distributed" groups of neurons. I don't understand the
facsination with this latest trend-- I have no objection
to it. I just don't understand how such a concept
is implemented in a model (such as pct) that USES
these perceptual representations. In PCT it is true
that perceptions (above level one) are implicitly
represented in the vector state of a number of
neurons - p = f (x1, x2,...xn) where the x's are the states
of the neuron's on which the perception depends. But the
model, in order to use the perecption implicit in
the vector, computes a signal, p; and the function, f,
determines which of the many pereptions implicit in
the vector is used in the model. My challenge to
Martin (and now Oded)  -- who appear to object to the
scaler representation of perceptions in the PCT model --
is simply -- show me what YOU have in mind as a way to
make "distributed" representations of perception usable
by the PCT model.

I have nothing personal against "distributed" models of
perception; just show me how such models can be used
as part of a WORKING PCT model.  Otherwise, such proposals
sound more like ideologies than models.

Thanks

Rick


     **************************************************************

Richard S. Marken                   USMail: 10459 Holman Ave
The Aerospace Corporation                   Los Angeles, CA 90024
E-mail: marken@aero.org
(310) 336-6214 (day)
(310) 474-0313 (evening)
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