Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!rutgers!sri-unix!ctnews!pyramid!prls!philabs!pwa-b!mmintl!franka
From: franka@mmintl.UUCP (Frank Adams)
Newsgroups: comp.ai,comp.cog-eng
Subject: Re: The symbol grounding problem: "Fuzzy" categories?
Message-ID: <2238@mmintl.UUCP>
Date: Wed, 1-Jul-87 21:44:00 EDT
Article-I.D.: mmintl.2238
Posted: Wed Jul  1 21:44:00 1987
Date-Received: Sat, 4-Jul-87 13:20:48 EDT
References: <764@mind.UUCP> <768@mind.UUCP> <770@mind.UUCP> <6174@diamond.BBN.COM> <1194@houdi.UUCP> <936@mind.UUCP>
Reply-To: franka@mmintl.UUCP (Frank Adams)
Organization: Multimate International, E. Hartford, CT.
Lines: 44
Xref: mnetor comp.ai:608 comp.cog-eng:177

In article <936@mind.UUCP> harnad@mind.UUCP (Stevan Harnad) writes:
|The question was: Do all-or-none categories (such as "bird") have "defining"
|features that can be used to sort members from nonmembers at the level of
|accuracy (~100%) with which we sort? However they are coded, I claim that
|those features MUST exist in the inputs and must be detected and used by the
|categorizer. A penguin is not a bird as a matter of degree, and the features
|that reliably assign it to "bird" are not graded.

I don't see how this follows.  It is quite possible to make all-or-none
judgements based on graded features.  Thermostats, for example, do it all
the time.  People do, too.  The examples which come to mind as being
obviously in this category are all judgements of actions to take based on
such features, not of categorization.  But then, we don't understand how we
categorize.

But to take an example of categorizing based on a graded feature.  Consider
a typical, unadorned, wooden kitchen chair.  We have no problem categorizing
this as a "chair".  Consider the same object, with no back.  This is
clearly categorized as a "stool", and not a "chair".  Now vary the size of
the back.  With a one inch back, the object is clearly still a "stool"; with
a ten inch back, it is clearly a "chair"; somewhere in between is an
ambiguous point.

I would assert that we *do*, in fact, make "all-or-none" type distinctions
based precisely on graded distinctions.  We have arbitrary (though vague)
cut off points where we make the distinction; and those cut off points are
chosen in such a way that ambiguous cases are rare to non-existent in our
experience[1].

In short, I see nothing about "all-or-none" categories which is not
explainable by arbitrary cutoffs of graded sensory data.

---------------
[1] There are some categories where this strategy does not work.  Colors are
a good example of this -- they vary over all of their range, with no very
rare points in it.  In this case, we use instead the strategy of large
overlapping ranges -- two people may disagree on whether a color should be
described as "blue" or "green", but both will accept "blue-green" as a
description.  The same underlying strategy applies: avoid borderline
situations.
-- 

Frank Adams                           ihnp4!philabs!pwa-b!mmintl!franka
Ashton-Tate          52 Oakland Ave North         E. Hartford, CT 06108