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Date:         Wed, 27 Jan 1993 16:14:18 -0700
From:         "William T. Powers" <POWERS_W%FLC@VAXF.COLORADO.EDU>
Subject:      Language models

[From Bill Powers (930127.1430)]

Bruce Nevin (930127.0854) and
Avery Andrews (930123.1350) --

Interesting. Here we are again. Operator grammar explains
language. Generative grammar explains language. Pick one to
believe, and the other is wrong. Obviously they can't both be
right. What basis can there be for anyone to believe either side?

I think there's a fundamental difference between the way the PCT
model is constructed and the way either Operator or Generative
grammar models are constructed. In Operator grammar you need to
know what words mean in order to distinguish operators from
arguments; in Generative grammar you need a lexicon of usage in
which word meanings have to be known to make any sense of it.
Suppose I were to give proponents of either side a sentence like
"Word1 Word222 Word17 Word9237 Word1403 ...". You couldn't even
divide that sentence into NP and VP. A lexicon made of such words
would be incomprehensible and useless. You couldn't make up a
list of operators and arguments because you'd have no way to know
whether a given word is an operator or an argument.

In a PCT model, however, we can speak of relationships among
perceptual, reference, error, and output signals inside the
system, and feedback functions and disturbances outside the
system, without ever specifying what the variables mean. The
model basically doesn't care WHAT is perceived or disturbed; the
fundamental relationships in the control loop are context-
independent. We can talk about control of input without ever
saying WHAT input. We can talk about loop gain, about stability,
about error sensitivity, about every parameter of control and
every law of control behavior without any lexicon or any list of
specific actions or controlled variables. Only when we test the
model experimentally do we give meanings to the controlled
variables, perceptual signals, output actions, and so forth. And
we expect the model to work correctly no matter what specific
meanings we give to these variables.

A model of language constructed in the same spirit as the PCT
model would not need a lexicon or empirical data on the way
specific words are used. Specific observations would be needed to
arrive at such a model, but once the model was constructed it
would no longer be cast in terms of specific observations.
Instead, there would be underlying principles that apply to any
way of hooking symbols to experiences, whatever the symbols and
whatever the experiences. In fact I doubt that this underlying
model would be a linguistic model at all: it would simply be one
application of a single model of perceptual control, the same
model that explains all behavior.

It's this concept of an underlying model that seems to me to be
missing from both the Operator and the Generative approaches. If
the apparent laws of language depend on specific word meanings,
they are not laws of language but only happenstance. Any other
laws would be just as likely, for all we can explain why they
exist.
---------------------------------------------------------------
Ed Ford (930127.1018) --

Those new rubber-band demos will take their place among the
fundamental set. I think that Occam's Law saying that we should
choose the simplest and most parsimonious explanation that covers
the facts ought to be supplemented by Occam's Economic Law: the
way of communicating the explanation should cost as little as
possible. You have taken a demonstration that could be done on a
$2000 computer and have managed to show every major point using
about 10 cents' worth of equipment. Very, very nice.
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Best to all,

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