Xref: utzoo comp.ai:3056 talk.philosophy.misc:1812 sci.lang:3895 Path: utzoo!attcan!uunet!lll-winken!ames!xanth!ukma!gatech!bloom-beacon!husc6!babbage!reiter From: reiter@babbage.harvard.edu (Ehud Reiter) Newsgroups: comp.ai,talk.philosophy.misc,sci.lang Subject: Re: Categorization Message-ID: <965@husc6.harvard.edu> Date: 11 Jan 89 20:56:51 GMT References: <681@cogsci.ucsd.EDU> <2959@uhccux.uhcc.hawaii.edu> <684@cogsci.ucsd.EDU> Sender: news@husc6.harvard.edu Reply-To: reiter@harvard.UUCP (Ehud Reiter) Organization: Aiken Computation Lab Harvard, Cambridge, MA Lines: 45 Steve Harnad writes: >I don't categorize a penguin as a bird "to a degree" -- it's a bird, all the >way, and I get it right every time. I do find it a less typical bird >than a robin. And if I introspect about HOW I manage to categorize it >as a bird, I probably can't come up with a set of features that are >necessary and sufficient to do so. But SOMETHING up there manages to >do it in my head, and it's then my job, not as introspector but as >empirical theorist, to try to come up with models for how that can be done. Personally, the only reason *I* categorize a penguin as a bird is that I was taught this in school. I doubt I would have put penguins in the same category as robins if I had made up my own categories. Indeed, many tribal languages use the category "flying animal" (includes bats but not ostriches) instead of "bird", and Lakoff points out in his book that the biologists themselves are debating what the "correct" taxonomic categories should be. The point, then, is that "bird" is a culturally defined and perhaps somewhat artificial category, and may not have a simple definition as a set of features. I also doubt *I* have a definition of "penguin" as a set of perceptual features. All the penguins I have ever seen have been in zoos, with signs telling me that they were penguins. I doubt I could reliably identify an animal as a penguin without the presence of those handy signs - but that doesn't stop me from knowing that the category "penguin" exists, and from being able to make inferences from the classification (i.e. if someone tells me that animal X is a penguin, I will infer that X likes cold weather). So, I can still use categorization information, even if I cannot define that category in terms of perceptual features. This is even more true for abstract categories - what set of perceptual features identify Republicans? Lawyers? Widows? In short, the reason I categorize a penguin as a bird is that I have been taught this as a rule - and the reason I categorize an object as a penguin is that a nearby sign tells me that the object is a penguin. Features have very little to do with the process. I'm not trying to say that people never categorize objects solely from perceptual information, because of course they do this sometimes. What I am saying is that there is a lot more to how categories are defined and used than perceptual features. Ehud Reiter reiter@harvard (ARPA,BITNET,UUCP) reiter@harvard.harvard.EDU (new ARPA)