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From: berleant@ut-sally.UUCP (Dan Berleant)
Newsgroups: comp.cog-eng
Subject: Re: The symbol grounding problem
Message-ID: <8310@ut-sally.UUCP>
Date: Mon, 22-Jun-87 06:25:37 EDT
Article-I.D.: ut-sally.8310
Posted: Mon Jun 22 06:25:37 1987
Date-Received: Tue, 23-Jun-87 03:53:57 EDT
References: <764@mind.UUCP> <768@mind.UUCP> <770@mind.UUCP> <6174@diamond.BBN.COM> <1166@houdi.UUCP> <861@mind.UUCP>
Reply-To: berleant@ut-sally.UUCP (Dan Berleant)
Organization: U. Texas CS Dept., Austin, Texas
Lines: 48

In article <861@mind.UUCP> harnad@mind.UUCP (Stevan Harnad) writes:
>My own alternative has to do with the way symbolic models work (and
>don't work). The hypothesis is that a hybrid symbolic/nonsymbolic
>model along the lines sketched above will be needed in order to pass
>the TTT. It will require a bottom-up, nonmodular grounding of its
>symbolic representations in nonsymbolic representations: iconic
>( = invertible with the sensory projection) and categorical ( = invertible
>only with the invariant features of category members that are preserved
>in the sensory projection and are sufficient to guide reliable
>categorization).

Are you saying that the categorical representations are to be
nonsymbolic?  The review of human concept representation I recently read
(Smith and Medin, Categories and Concepts, 1981) came down so hard on
the holistic theory of concept representation that I must admit I
skipped the chapter. I remember some statement like 'this approach is
easy to criticize' and skipped the rest. The alternative nonsymbolic
approach would be the 'dimensional' one. It seems a strongish
statement to say that this would be sufficient, to the exclusion of
symbolic properties. For example, if one were to say that a property
of the concept "human" is "breathes", insisting on a continuous
dimension for this property might be iffy. But it might be correct.
An iron lung would be lower on the scale than ordinary breathing.
Rate and depth of respiration would be a factor -- a rate and depth
typical of a mouse would count against identifying X as human.
Visible heaving would be higher on the scale than a lack of firm
observation. Any opinions out there??
   However, the metric hypothesis -- that a concept is sufficiently
characterized by a point in a multi-dimensional space -- seems wrong,
as experiments have shown.
   I'm uncomfortable about another aspect of the quoted paragraph.  To
discuss "invariant features... sufficient to guide reliable
categorization" sounds like the "classical" theory (as Smith & Medin
call it) of concept representation: Concepts are represented as
necessary and sufficient features (i.e., there are defining features,
i.e. there is a boolean conjunction of predicates for a concept).  This
approach has serious problems, not the least of which is the inability
of humans to describe these features for seemingly elementary concepts,
like "chair", as Weinstein and others point out. I contend that a
boolean function (including ORs as well as ANDs) could work, but that
is not what was mentioned. An example might be helpful: A vehicle must
have a steering wheel OR handlebars. But to remove the OR by saying,
a vehicle must have a means of steering, is to rely on a feature which
is symbolic, high level, functional, which I gather we are not allowing.

Dan Berleant
UUCP: {gatech,ucbvax,ihnp4,seismo...& etc.}!ut-sally!berleant
ARPA: ai.berleant@r20.utexas.edro