On Fri, Oct 10, 2008 at 8:03 PM, Ben Goertzel <[EMAIL PROTECTED]> wrote: > > Yah, according to Bayes rule if one assumes P(bird) = P(swimmer) this would > be the case... > > (Of course, this kind of example is cognitively misleading, because if the > only knowledge > the system has is "Swallows are birds" and "Swallows are NOT swimmers" then > it doesn't > really know that the terms involved are "swallows", "birds", "swimmers" etc. > ... then in > that case they're just almost-meaningless tokens to the system, right?)
Well, it depends on the semantics. According to model-theoretic semantics, if a term has no reference, it has no meaning. According to experience-grounded semantics, every term in experience have meaning --- by the role it plays. Further questions: (1) Don't you intuitively feel that the evidence provided by non-swimming birds says more about "Birds are swimmers" than "Swimmers are birds"? (2) If your answer for (1) is "yes", then think about "Adults are alcohol-drinkers" and "Alcohol-drinkers are adults" --- do they have the same set of counter examples, intuitively speaking? (3) According to your previous explanation, will PLN also take a red apple as negative evidence for "Birds are swimmers" and "Swimmers are birds", because it reduces the "candidate pool" by one? Of course, the probability adjustment may be very small, but qualitatively, isn't it the same as a non-swimming bird? If not, then what the system will do about it? Pei > > On Fri, Oct 10, 2008 at 7:34 PM, Pei Wang <[EMAIL PROTECTED]> wrote: >> >> Ben, >> >> I see your position. >> >> Let's go back to the example. If the only relevant domain knowledge >> PLN has is "Swallows are birds" and "Swallows are >> NOT swimmers", will the system assigns the same lower-than-default >> probability to "Birds are swimmers" and "Swimmers are birds"? Again, >> I only need a qualitative answer. >> >> Pei >> >> On Fri, Oct 10, 2008 at 7:24 PM, Ben Goertzel <[EMAIL PROTECTED]> wrote: >> > >> > Pei, >> > >> > I finally took a moment to actually read your email... >> > >> >> >> >> >> >> However, the negative evidence of one conclusion is no evidence of the >> >> other conclusion. For example, "Swallows are birds" and "Swallows are >> >> NOT swimmers" suggests "Birds are NOT swimmers", but says nothing >> >> about whether "Swimmers are birds". >> >> >> >> Now I wonder if PLN shows a similar asymmetry in induction/abduction >> >> on negative evidence. If it does, then how can that effect come out of >> >> a symmetric truth-function? If it doesn't, how can you justify the >> >> conclusion, which looks counter-intuitive? >> > >> > According to Bayes rule, >> > >> > P(bird | swimmer) P(swimmer) = P(swimmer | bird) P(bird) >> > >> > So, in PLN, evidence for P(bird | swimmer) will also count as evidence >> > for P(swimmer | bird), though potentially with a different weighting >> > attached to each piece of evidence >> > >> > If P(bird) = P(swimmer) is assumed, then each piece of evidence >> > for each of the two conditional probabilities, will count for the other >> > one symmetrically. >> > >> > The intuition here is the standard Bayesian one. >> > Suppose you know there >> > are 10000 things in the universe, and 1000 swimmers. >> > Then if you find out that swallows are not >> > swimmers ... then, unless you think there are zero swallows, >> > this does affect P(bird | swimmer). For instance, suppose >> > you think there are 10 swallows and 100 birds. Then, if you know for >> > sure >> > that swallows are not swimmers, and you have no other >> > info but the above, your estimate of P(bird|swimmer) >> > should decrease... because of the 1000 swimmers, you now know there >> > are only 990 that might be birds ... whereas before you thought >> > there were 1000 that might be birds. >> > >> > And the same sort of reasoning holds for **any** probability >> > distribution you place on the number of things in the universe, >> > the number of swimmers, the number of birds, the number of swallows. >> > It doesn't matter what assumption you make, whether you look at >> > n'th order pdf's or whatever ... the same reasoning works... >> > >> > From what I understand, your philosophical view is that it's somehow >> > wrong for a mind to make some assumption about the pdf underlying >> > the world around it? Is that correct? If so I don't agree with this... >> > I >> > think this kind of assumption is just part of the "inductive bias" with >> > which >> > a mind approaches the world. >> > >> > The human mind may well have particular pdf's for stuff like birds and >> > trees wired into it, as we evolved to deal with these things. But >> > that's >> > not really the point. The inductive bias may be much more abstract -- >> > ultimately, it can just be an "occam bias" that biases the mind to >> > prior distributions (over the space of procedures for generating >> > prior distributions for handling specific cases) >> > that are simplest according to some wired-in >> > simplicity measure.... >> > >> > So again we get back to basic differences in philosophy... >> > >> > -- Ben G >> > >> > >> > >> > >> > >> > >> > ________________________________ >> > agi | Archives | Modify Your Subscription >> >> >> ------------------------------------------- >> agi >> Archives: https://www.listbox.com/member/archive/303/=now >> RSS Feed: https://www.listbox.com/member/archive/rss/303/ >> Modify Your Subscription: https://www.listbox.com/member/?&; >> Powered by Listbox: http://www.listbox.com > > > > -- > Ben Goertzel, PhD > CEO, Novamente LLC and Biomind LLC > Director of Research, SIAI > [EMAIL PROTECTED] > > "Nothing will ever be attempted if all possible objections must be first > overcome " - Dr Samuel Johnson > > > ________________________________ > agi | Archives | Modify Your Subscription ------------------------------------------- agi Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/ Modify Your Subscription: https://www.listbox.com/member/?member_id=8660244&id_secret=114414975-3c8e69 Powered by Listbox: http://www.listbox.com
