Xref: utzoo comp.ai:3055 talk.philosophy.misc:1811 sci.lang:3893 Path: utzoo!utgpu!watmath!clyde!att!osu-cis!killer!mit-eddie!uw-beaver!cornell!turney From: turney@svax.cs.cornell.edu (Jenn Turney) Newsgroups: comp.ai,talk.philosophy.misc,sci.lang Subject: Re: Categorization Message-ID: <24080@cornell.UUCP> Date: 11 Jan 89 20:57:15 GMT References: <2980@uhccux.uhcc.hawaii.edu> Sender: nobody@cornell.UUCP Reply-To: turney@svax.cs.cornell.edu (Jenn Turney) Organization: Cornell Univ. CS Dept, Ithaca NY Lines: 57 In article harnad@elbereth.rutgers.edu (Stevan Harnad) writes: > > >In Article 3140 of comp.ai, lee@uhccux.uhcc.hawaii.edu (Greg Lee) >of University of Hawaii asks: > >" Why does T presuppose a mechanism for C? > >Because to judge how typical an X an X is I must first be able to judge >that it's an X. > >" If 40%-X and 89%-X are grades, then so is 100%-X a grade. >" If you have T, C can be described as a special case of it. > >40% what? 89% what? If you don't have a 100% category in the first >place for whatever you have a graded quantity of, you have an >incoherent concept or an infinite regress. Suppose gold was, by its >nature, an alloy, i.e., K% lead and (100 - k)% "gold." Now what was >that SECOND stuff I just mentioned? (Once you have C, T can be described >as a special case of it, not vice versa.) > This argument is specious. Deriving concept membership (categorization) from typicality ratings is not automatic. It is entirely possible for something to receive a typicality rating for a category without any knowledge about whether it actually belongs to the category. Suppose you encounter a new creature in the wild which has wings and feathers, flies, and has a trunk. You don't know whether it's a bird or not but if you were asked to rate its typicality of the category "bird", it's very likely that you would give a non-zero rating. It may still be possible to derive C from typicality ratings; however, the dilemma now is determining where the dividing line is. Perhaps all instances with typicality ratings higher than 15% are members of the category. (Another case: wouldn't you say a panda was a pretty typical bear, even though pandas are in the raccoon family, not the bear family?) As regards the statement that categories are either 100% or incoherent, I'll remind you of the results of Armstrong, Gleitman and Gleitman. They asked subjects to give typicality ratings of numbers for the category "even number". Surprise -- 4 is a more typical (better exemplar) even number than 806. The obvious next question is, how relevant is "typicality"? Is it the right term to use -- would using another term improve the situation? Reference: Armstrong, S. L., L. R. Gleitman, H. Gleitman (1983). What some concepts might not be. _Cognition_, 13, 263-308. ________ | | Jenn | | turney@svax.cs.cornell.edu | let us all be born just one more time | | | Dept. of Computer Science | we may yet get it \_| | Cornell University | right