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From: marty1@houdi.UUCP (M.BRILLIANT)
Newsgroups: comp.ai,comp.cog-eng
Subject: Re: The symbol grounding problem
Message-ID: <1152@houdi.UUCP>
Date: Thu, 11-Jun-87 11:24:22 EDT
Article-I.D.: houdi.1152
Posted: Thu Jun 11 11:24:22 1987
Date-Received: Sat, 20-Jun-87 10:34:47 EDT
References: <764@mind.UUCP> <768@mind.UUCP> <770@mind.UUCP> <6174@diamond.BBN.COM> <828@mind.UUCP>
Organization: AT&T Bell Laboratories, Holmdel
Lines: 54
Keywords: icons, categories, symbols, grounding, modularity, cognition
Summary: Human visual processing is neither analog nor invertible.
Xref: mnetor comp.ai:541 comp.cog-eng:128

In article <828@mind.UUCP>, harnad@mind.UUCP (Stevan Harnad) writes:
> aweinste@Diamond.BBN.COM (Anders Weinstein) of BBN Laboratories, Inc.,
> Cambridge, MA writes:
> 
> >	There's no [symbol] grounding problem, just the old
> >	behavior-generating problem
> 
> ..... There is:
> (1) the behavior-generating problem (what I have referred to as the problem of
> devising a candidate that will pass the Total Turing Test), (2) the
> symbol-grounding problem (the problem of how to make formal symbols
> intrinsically meaningful, independent of our interpretations), and (3) ...

Just incidentally, what is the intrinsic meaning of "intrinsically
meaningful"?  The Turing test is an objectively verifiable criterion.
How can we objectively verify intrinsic meaningfulness?

> .... Add to this the surprising logical consequence that a
> "dedicated" digital system (hardwired to its peripherals) would be
> "analog" in its invertible inputs and outputs according to my
> invertibility criterion, .....

Using "analog" to mean "invertible" invites misunderstanding, which
invites irrelevant criticism.

Human (in general, vertebrate) visual processing is a dedicated
hardwired digital system.  It employs data reduction to abstract such
features as motion, edges, and orientation of edges.  It then forms a
map in which position is crudely analog to the visual plane, but
quantized.  This map is sufficiently similar to maps used in image
processing machines so that I can almost imagine how symbols could be
generated from it.

By the time it gets to perception, it is not invertible, except with
respect to what is perceived.  Noninvertibility is demonstrated in
experiments in the identification of suspects.  Witnesses can report
what they perceive, but they don't always perceive enough to invert
the perceived image and identify the object that gave rise to the
perception.  If you don't agree, please give a concrete, objectively
verifiable definition of "invertibility" that can be used to refute my
conclusion.

If I am right, human intelligence itself relies on neither analog nor
invertible symbol grounding, and therefore artificial intelligence
does not require it.

By the way, there is an even simpler argument: even the best of us can
engage in fuzzy thinking in which our symbols turn out not to be
grounded.  Subjectively, we then admit that our symbols are not
intrinsically meaningful, though we had interpreted them as such.

M. B. Brilliant					Marty
AT&T-BL HO 3D-520	(201)-949-1858
Holmdel, NJ 07733	ihnp4!houdi!marty1