Xref: utzoo comp.ai:3087 talk.philosophy.misc:1831 sci.lang:3934 Path: utzoo!attcan!uunet!ncrlnk!ncrcae!hubcap!gatech!cwjcc!hal!nic.MR.NET!indri!csd4.milw.wisc.edu!leah!itsgw!nyser!njin!aramis.rutgers.edu!elbereth.rutgers.edu!harnad From: harnad@elbereth.rutgers.edu (Stevan Harnad) Newsgroups: comp.ai,talk.philosophy.misc,sci.lang Subject: Re: Categorization Summary: Categorization: Competence vs. Performance Message-ID: Date: 14 Jan 89 07:51:33 GMT References: <681@cogsci.ucsd.EDU> <2959@uhccux.uhcc.hawaii.edu> <687@cogsci.ucsd.EDU> Organization: Rutgers Univ., New Brunswick, N.J. Lines: 116 zhang@cogsci.ucsd.EDU (Jiajie Zhang) of Institute for Cognitive Science, UC San Diego writes: " I agree that judgements of typicality can't provide us much " information about the underlying mechanism of categorization... " [but] our ability to perform categorization is just one of several " important aspects of categorization... In this passage Zhang agrees with most of the points I have been making in these postings, so I cannot disagree, but I would say that our ability to perform categorizations is by far the most important aspect of categorization; the rest is little more than fine tuning once you solve that problem. Among the other aspects of categorization Zhang cites: " (1) Descriptive analyses of categories... (e.g., biological taxonomy, " Keil's ontological categories.) Biological taxonomy is probably best left to biologists. What can psychologists and computer scientists offer to the specialists here? The same is true for ontology. (And Keil, by the way, is not doing ontology, even if he says so: He is studying the development of ontological concepts -- concepts of what there is.) On the other hand, one is free to gather one's insights where one may, and if biology or ontology gives someone an idea about how we manage to categorize, fine. And, human categorization PERFORMANCE in any domain, including biology and ontology, certainly counts as data. " (2) Internal representations of categories... A theory of " categorization should not only answer the question of what are the " structures of internal representation of categories but also the " question of HOW human beings actually DO the categorization. It should " also be able to explain empirical data, such as prototypical effects. " Connectionism, in my opinion, might be the best tool (so far) to study " categorization... For me, the question of how categories are internally represented and the question of how we do categorization are the same question (the basic question mentioned at the outset). The internal representation is the mechanism subserving the categorization performance. I agree that connectionism might be a candidate mechanism, particularly for category learning and feature detection. Prototype effects should certainly be explained, but categorization itself must be explained first; once it is, I predict that prototype effects will turn out to be a minor side-effect. I certainly wouldn't "constrain" my categorization models at this stage to conform to prototype effects -- any more than I would constrain them to conform to reaction time, brain-damage effects or our foggy knowledge of brain function. Let models achieve success at lifesize categorization any-which-way first and then let's worry about fine-tuning them to exhibit those extra frills. On the other hand, as suggested before, we are free to gather INSIGHT wherever we may; so if prototype effects, brain-damage data or neurobiological data inspire anyone to a working categorization model, bravo! But the only CONSTRAINT we need on the project is provided by the evidence of our actual categorization performance capacity itself. " (3) Origin of categories, both ontogenetically and phylogenetically. " Do categories exist objectively out there and wait for " human beings to find the regularities and pick them up? To what " extent are categories artificial, that is, to what extent do human " beings impose artificial categories on nature? Learning " categories through schooling is different from that through " discovering, and that through creating. Developmental data on categorization performance are of course important, because they provide some insight into the all-important process of the acquisition of categories (including MIScategorization and the input needed to correct it). Comparative data on other species are of course relevant too. On the other hand, as I suggested, I think cognitive scientists would do better to avoid the minefields of ontology -- at least if they are not prepared first to arm themselves with two millenia of philosophy. This much, however, looks as if it can be said with some confidence: Objective categories -- i.e., those for which there are objective consequences arising from miscategorizations -- must have a basis in objective, discernible external features. Why we PICK OUT those categories and those features may sometimes be socially determined, but that does not make the features any less external. I agree that learning categories from cases is importantly different from learning them through instruction; and that the "creation" of categories is yet another relevant aspect of performance. My own theory addresses all of these cases explicitly. " (4) Why do human beings categorize things? I think this might be " related to what Harnad called miscategorization. Personally, I think " this is a question about cognitive cost. Categorization is merely a special form of differential responding to input. Differential responding is guided by its consequences. We must categorize things because there is a cost (in survival or well-being) to miscategorizing them. I don't know what "cognitive cost" means, but I think miscategorization is all-important because that is what provides the feedback that allows us to converge on the features that eventually allow us to get the categorization right. And if there is no right or wrong to a category, as I said in another posting, then all we have is subjective similarity judgment. " (5) Relation between performance and competence of categorization Our category competence is our capacity to categorize as we do, given the inputs we get, and the feedback from the consequences of our attempts. And just as in the linguistic competence/performance distinction, there are performance details (such as prototype effects and introspections about features) that are not central to the basic problem of modeling the competence. (When I say "categorization performance capacity" I mean category competence, not performance.) -- Stevan Harnad INTERNET: harnad@confidence.princeton.edu harnad@princeton.edu srh@flash.bellcore.com harnad@elbereth.rutgers.edu harnad@princeton.uucp BITNET: harnad@pucc.bitnet CSNET: harnad%princeton.edu@relay.cs.net (609)-921-7771