Path: utzoo!attcan!uunet!husc6!bloom-beacon!doc.ic.ac.UK!sme From: sme@doc.ic.ac.UK Newsgroups: comp.ai.digest Subject: Re: Generality in Artificial Intelligence Message-ID: <19880718040717.9.NICK@HOWARD-JOHNSONS.LCS.MIT.EDU> Date: 18 Jul 88 04:07:00 GMT Sender: daemon@bloom-beacon.MIT.EDU Organization: The Internet Lines: 128 Approved: ailist@ai.ai.mit.edu From: mcvax!doc.ic.ac.uk!sme@uunet.UU.NET Date: Thu, 14 Jul 88 10:06 EDT To: AIList@ai.ai.mit.edu Newsgroups: comp.ai.digest Subject: Re: Generality in Artificial Intelligence Summary: Expires: References: <19880712044954.9.NICK@HOWARD-JOHNSONS.LCS.MIT.EDU> Sender: Reply-To: Steve M Easterbrook Followup-To: Distribution: Organization: Dept. of Computing, Imperial College, London, UK. Keywords: In a previous article, YLIKOSKI@FINFUN.BITNET writes: >> "In my opinion, getting a language for expressing general >> commonsense knowledge for inclusion in a general database is the key >> problem of generality in AI." >... >Here follows an example where commonsense knowledge plays its part. A >human parses the sentence > >"Christine put the candle onto the wooden table, lit a match and lit >it." > >The difficulty which humans overcome with commonsense knowledge but >which is hard to a program is to determine whether the last word, the >pronoun "it" refers to the candle or to the table. After all, you can >burn a wooden table. > >Probably a human would reason, within less than a second, like this. > >"Assume Christine is sane. The event might have taken place at a >party or during her rendezvous with her boyfriend. People who do >things such as taking part in parties most often are sane. > >People who are sane are more likely to burn candles than tables. > >Therefore, Christine lit the candle, not the table." Aren't you overcomplicating it a wee bit? My brain would simply tell me that in my experience, candles are burnt much more often than tables. QED. This to me, is very revealing. The concept of commonsense knowledge that McCarthy talks of is simply a huge base of experience built up over a lifetime. If a computer program was switched on for long enough, with a set of sensors similar to those provided by the human body, and a basic abililty to go out and do things, to observe and experiment, and to interact with people, it would be able to gather a similar set of experiences to those possessed by humans. The question is then whether the program can store and index those experiences, in their totality, in some huge episodic memory, and whether it has the appropriate mechanisms to fire useful episodic recalls at useful moments, and apply those recalls to the present situation, whether by analogy or otherwise. From this, it seems to me that the most important task that AI can address itself to at the present is the study of episodic memory: how it can be organised, how it can be accessed, and how analogies with past situations can be developed. This should lead to a theory of experience, ready for when robotics and memory capacities are advanced enough for the kind of exeriment I descibed above. With all due respect to McCarthy et al, attempts to hand code the wealth of experience of the real world that adult human beings have accumulated are going to prove futile. Human intelligence doesn't gather this commonsense by being explicitly programmed with rules (formal OR informal), and neither will artificial intelligences. >It seems to me that the inferences are not so demanding but the >inferencer utilizes a large amount of background knowledge and a good >associative access mechanism. Yes. Work on the associative access, and let the background knowledge evolve itself. >... >What kind of formalism should we use for expressing the commonsense >knowledge? Try asking what kind of formalism should we use for expressing episodic memories? Later on you suggest natural language. Is this suitable? Do people remember things by describing them in words to themselves? Or do they just create private "symbols", or brain activation patterns, which only need to be translated into words when being communicated to others? Note: I am not saying people don't think in natural language, only that they don't store memories as natural language accounts. I don't think this kind of experience can be expressed in any formalism, nor do I think it can be captured by natural language. It needs to evolve as a private set of informal symbols, of which the brain (human or computer) does not need to consciously realise are there. All it needs to do is associate the right thought with the symbols when they are retrieved, i.e. to interpret the memories. Again I think this kind of ability evolves with experience: at first, symbols (brain activity patterns) would be triggered which the brain would be unable to interpret. If this is beginning to sound like an advocation of neural nets/connectionist learning, then so be it. I feel that a conventional AI system coupled to a connectionist net for its episodic memory might be a very sensible achitecture. There are probably other ways of achieving the same behaviour, I don't know. One final note. Read the first chapter of the Dreyfus and Dreyfus book "Mind over Machine", for a thought-provoking account of how experts perform, using "intuition". Logic is only used in hindsight to support an intuitive choice. Hence "heuristics is compiled hindsight". Being arch-critics of AI, the Dreyfuses conclude that the intuition that experts develop is intrinsically human and can never be reproduced by machine. Being an AI enthusiast, I conclude that intuition is really the unconscious application of experience, and all that's needed to reproduce it is the necessary mechanisms for storing and retrieving episodic memories by association. >In my opinion, it is possible that an attempt to express commonsense >knowledge with a formalism is analogous to an attempt to fit a whale >into a tin sardine can. ... I agree. How did you generate this analogy? Is it because you had a vast amount of common sense knowledge about whales and sardines, and tins, (whether expressed in natural language (vast!), or some formal system) through which you had to wade to realise that sardines will fit in small tins but whales will not, and eventually synthesis this particular concept, or did you just try to recall (holistically) an image that matched the concept of forcing a huge thing into a rigid container? Steve Easterbrook.