Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!ll-xn!husc6!diamond.bbn.com!aweinste From: aweinste@diamond.bbn.com.UUCP Newsgroups: comp.ai,comp.cog-eng Subject: Re: The symbol grounding problem Message-ID: <6453@diamond.BBN.COM> Date: Tue, 9-Jun-87 18:12:32 EDT Article-I.D.: diamond.6453 Posted: Tue Jun 9 18:12:32 1987 Date-Received: Sat, 13-Jun-87 04:27:05 EDT References: <764@mind.UUCP> <768@mind.UUCP> <770@mind.UUCP> <6174@diamond.BBN.COM> <6358@diamond.BBN.COM> <812@mind.UUCP> Reply-To: aweinste@Diamond.BBN.COM (Anders Weinstein) Organization: BBN Laboratories, Inc., Cambridge, MA Lines: 93 Keywords: icons, categories, symbols, grounding, modularity, cognition Xref: utgpu comp.ai:468 comp.cog-eng:108 Summary: There's no grounding problem, just the old behavior-generating problem In article <812@mind.UUCP> Stevan Harnad replies: With regard physical invertibility and the A/D distinction: > >> a *digitized* image -- in your terms... is "analog" in the >> information it preserves and not in the information lost. This >> seems to me to be a very unhappy choice of terminology! > > For the time being, I've acknowledged that >my invertibility criterion is, if not necessarily unhappy, somewhat >surprising in its implications, for it implies (1) that being analog >may be a matter of degree (i.e., degree of invertibility) and (2) even >a classical digital system must be regarded as analog to a degree ... Grumble. These consequences only *seem* surprising if we forget that you've redefined "analog" in a non-standard manner; this is precisely I why I keep harping on your terminology. Compare them with what you're really saying: "physical invertibility is a matter of degree" or "a classical digital system still employs physically invertible representations" -- both quite humdrum. With regard to the symbolic AI approach to the "symbol-grounding problem": > >One proposal, as you note, is that a pure symbol-manipulating system can be >"grounded" by merely hooking it up causally in the "right way" to the outside >world with simple (modular) transducers and effectors. ... I have argued >that [this approach] simply won't succeed in the long run (i.e., as we >attempt to approach an asymptote of total human performance capacity ...) >...In (1) a "toy" case ... the right causal connections could be wired >according to the human encryption/decryption scheme: Inputs and outputs could >be wired into their appropriate symbolic descriptions. ... But none but the >most diehard symbolic functionalist would want to argue that such a simple >toy model was "thinking," ... The reason is that we are capable of >doing *so much more* -- and not by an assemblage of endless independent >modules of essentially the same sort as these toy models, but by some sort of >(2) integrated internal system. Could that "total" system be just an >oversized toy model -- a symbol system with its interpretations "fixed" by a >means analogous to these toy cases? I am conjecturing that it is not. I think your reply may misunderstand the point of my objection. I'm not trying to defend the intentionality of "toy" programs. I'm not even particularly concerned to *defend* the symbolic approach to AI (I personally don't even believe in it). I'm merely trying to determine exactly what your argument against symbolic AI is. I had thought, perhaps wrongly, that you were claiming that the interpretations of systems conceived by symbolic AI system must somehow inevitably fail to be "grounded", and that only a system which employed "analog" processing in the way you suggest would have the causal basis required for fixing an interpretation. In response, I pointed out first that advocates of the symbolic approach already understand that causal commerce with the environment is necessary for intentionality: they envision the use of complex perceptual systems to provide the requisite "grounding". So it's not as though the symbolic approach is indifferent to this issue. And your remarks against "toy" systems and "hard-wiring" the interpretations of the inputs are plain unfair -- the symbolic approach doesn't belittle the importance or complexity of what perceptual systems must be able to do. It is in total agreement with you that a truly intentional system must be capable of complex adaptive performance via the use of its sensory input -- it just hypothesizes that symbolic processing is sufficient to achieve this. And, as I tried to point out, there is just no reason that a modular, all-digital system of the kind envisioned by the symbolic approach could not be entirely "grounded" BY YOUR OWN THEORY OF "GROUNDEDNESS": it could employ "physically inevertible" representations (only they would be digital ones), from these it could induct reliable "feature filters" based on training (only these would use digital rather than analog techniques), etc. I concluded that the symbolic approach appears to handle your so-called "grounding problem" every bit as well as any other method. Now comes the reply that you are merely conjecturing that analog processing may be required to realize the full range of human, as opposed to "toy", performance -- in short, you think the symbolic approach just won't work. But this is a completely different issue! It has nothing to do with some mythical "symbol grounding" problem, at least as I understand it. It's just the same old "intelligent-behavior-generating" problem which everyone in AI, regardless of paradigm, is looking to solve. From this reply, it seems to me that this alleged "symbol-grounding problem" is a real red-herring (it misled me, at least). All you're saying is that you suspect that mainstream AI's symbol system hypothesis is false, based on its lack of conspicuous performance-generating sucesses. Obviously everyone must recognize that this is a possibility -- the premise of symbolic AI is, after all, only a hypothesis. But I find this a much less interesting claim than I originally thought -- conjectures, after all, are cheap. It *would* be interesting if you could show, as, say, the connectionist program is trying to, how analog processing can work wonders that symbol-manipulation can't. But this would require detailed research, not speculation. Until then, it remains a mystery why your proposed approach should be regarded as any more promising than any other. Anders Weinstein BBN Labs