Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!ames!ptsfa!ihnp4!homxb!houxm!houdi!marty1 From: marty1@houdi.UUCP Newsgroups: comp.ai,comp.cog-eng Subject: Re: The symbol grounding problem Message-ID: <1164@houdi.UUCP> Date: Sun, 14-Jun-87 10:15:55 EDT Article-I.D.: houdi.1164 Posted: Sun Jun 14 10:15:55 1987 Date-Received: Sun, 14-Jun-87 23:36:18 EDT References: <764@mind.UUCP> <768@mind.UUCP> <770@mind.UUCP> <6174@diamond.BBN.COM> <835@mind.UUCP> Organization: AT&T Bell Laboratories, Holmdel Lines: 113 Keywords: icons, categories, symbols, grounding, modularity, cognition Xref: utgpu comp.ai:480 comp.cog-eng:112 Summary: There's more than just firing frequency. In article <835@mind.UUCP>, harnad@mind.UUCP (Stevan Harnad) writes: > marty1@houdi.UUCP (M.BRILLIANT) of AT&T Bell Laboratories, Holmdel writes: > > > Human visual processing is neither analog nor invertible. > > Nor understood nearly well enough to draw the former two conclusions, > it seems to me. If you are taking the discreteness of neurons, the > all-or-none nature of the action potential, and the transformation of > stimulus intensity to firing frequency as your basis for concluding > that visual processing is "digital," the basis is weak, and the > analogy with electronic transduction strained. No, I'm taking more than that as the basis. I don't have any names handy, and I'm not a professional in neurobiology, but I've seen many articles in Science and Scientific American (including a classic paper titled something like "What the frog's eye tells the frog's brain") that describe the flow of visual information through the layers of the retina, and through the layers of the visual cortex, with motion detection, edge detection, orientation detection, etc., all going on in specific neurons. Maybe a neurobiologist can give a good account of what all that means, so we can guess whether computer image processing could emulate it. > > what is the intrinsic meaning of "intrinsically meaningful"? > > The Turing test is an objectively verifiable criterion. How can > > we objectively verify intrinsic meaningfulness? > > We cannot objectively verify intrinsic meaningfulness. The Turing test > is the only available criterion. Yet we can make inferences... I think that substantiates Weinstein's position: we're back to the behavior-generating problem. > ....: We > know the difference between looking up a meaning in an English/English > dictionary versus a Chinese/Chinese dictionary (if we are nonspeakers > of Chinese): The former symbols are meaningful and the latter are > not. Not relevant. Intrinsically, words in both languages are equally meaningful. > > Using "analog" to mean "invertible" invites misunderstanding, > > which invites irrelevant criticism. > > ..... I have acknowledged all > along that the physically invertible/noninvertible distinction may > turn out to be independent of the A/D distinction, although the > overlap looks significant. And I'm doing my best to sort out the > misunderstandings and irrelevant criticism... Then please stop using the terms analog and digital. > > > Human (in general, vertebrate) visual processing is a dedicated > > hardwired digital system. It employs data reduction to abstract such > > features as motion, edges, and orientation of edges. It then forms a > > map in which position is crudely analog to the visual plane, but > > quantized. This map is sufficiently similar to maps used in image > > processing machines so that I can almost imagine how symbols could be > > generated from it. > > I am surprised that you state this with such confidence. In > particular, do you really think that vertebrate vision is well enough > understood functionally to draw such conclusions? ... Yes. See above. > ... And are you sure > that the current hardware and signal-analytic concepts from electrical > engineering are adequate to apply to what we do know of visual > neurobiology, rather than being prima facie metaphors? Not the hardware concepts. But I think some principles of information theory are independent of the medium. > > By the time it gets to perception, it is not invertible, except with > > respect to what is perceived. Noninvertibility is demonstrated in > > experiments in the identification of suspects. Witnesses can report > > what they perceive, but they don't always perceive enough to invert > > the perceived image and identify the object that gave rise to the > > perception.... > > .... If I am right, human intelligence itself relies on neither > > analog nor invertible symbol grounding, and therefore artificial > > intelligence does not require it. > > I cannot follow your argument at all. Inability to categorize and identify > is indeed evidence of a form of noninvertibility. But my theory never laid > claim to complete invertibility throughout..... First "analog" doesn't mean analog, and now "invertibility" doesn't mean complete invertibility. These arguments are getting too slippery for me. > .... Categorization and identification > itself *requires* selective non-invertibility: within-category differences > must be ignored and diminished, while between-category differences must > be selected and enhanced. Well, that's the point I've been making. If non-invertibility is essential to the way we process information, you can't say non-invertibility would prevent a machine from emulating us. Anybody can do hand-waving. To be convincing, abstract reasoning must be rigidly self-consistent. Harnad's is not. I haven't made any assertions as to what is possible. All I'm saying is that Harnad has come nowhere near proving his assertions, or even making clear what his assertions are. M. B. Brilliant Marty AT&T-BL HO 3D-520 (201)-949-1858 Holmdel, NJ 07733 ihnp4!houdi!marty1