mmt@client2.UUCP (Martin Taylor) (09/26/88)
---- Forwarded Message Follows ---- Return-path: <@AI.AI.MIT.EDU:ailist-request@AI.AI.MIT.EDU> Received: from AI.AI.MIT.EDU by ZERMATT.LCS.MIT.EDU via CHAOS with SMTP id 195782; 21 Sep 88 07:04:56 EDT Received: from BLOOM-BEACON.MIT.EDU (TCP 2224000021) by AI.AI.MIT.EDU 21 Sep 88 07:11:45 EDT Received: by BLOOM-BEACON.MIT.EDU with sendmail-5.59/4.7 id <AA03415@BLOOM-BEACON.MIT.EDU>; Wed, 21 Sep 88 06:54:06 EDT Received: from USENET by bloom-beacon.mit.edu with netnews for ailist@ai.ai.mit.edu (ailist@ai.ai.mit.edu) (contact usenet@bloom-beacon.mit.edu if you have questions) Date: 2 Sep 88 22:35:01 GMT From: mnetor!utzoo!dciem!dretor!client2!mmt@uunet.uu.net (Martin Taylor) Organization: D.C.I.E.M., Toronto, Canada Subject: Theft or Honest Toil, (was Re: Pinker & Prince Reply (long version)) Message-Id: <995@client2.DRETOR.UUCP> References: <2816@mind.UUCP>, <2817@mind.UUCP>, <2818@mind.UUCP> Sender: ailist-request@ai.ai.mit.edu To: ailist@ai.ai.mit.edu Harnad characterizes learning rules from a rule-provider as "theft", whereas obtaining them by evaluation of the statistics of input data is "honest toil". But the analogy is perhaps better in a different domain: learning by evaluating the statistics of the environment is like building up amino acids and other nutritious things from inorganic molecules through photosynthesis, whereas obtaining rules from rule-providers is like eating already built nutritious things. One ofthe great advantages of language is that we CAN take advantage of the regularities discovered in the data by other people. The rules they tell us may be wrong, but to use them is easier than to discover our own rules. It is hardly to be taken as an analogy to "theft". If we look at early child learning, the "theft" question becomes: Has evolution provided us with a set of rules that we do not have to obtain from the data, so that we can later obtain more rules from people who did themselves learn from data? Obviously in some sense the answer is "yes" there are SOME innate rules regarding how we interpret sensory input, even if those rules are as low-level as to indicate how to put together a learning net. Obviously, also, there are MANY rules that we have to get from the data and/or from people who learned them from the data. The question then becomes whether the "rules" regarding past-tense formation are of the innate kind, of the data-induced kind, or of the passed-on kind. My understanding of the developmental literature is that children pass through three phases: (i) correct past-tense formation for those verbs for which the child uses the past tense frequently; (ii) false regularization, in which non-regular past tenses (went) are replaced by regularized ones (goed); (iii) more-or-less correct past tense formation, in which exceptions are properly used, AND novel or neologized verbs are given regular past tenses (in some sense of regular). This sequence suggests to me that the pattern does not have any innate rule component. Initially, all words are separate, in the sense that "went" is a different word from "go". Later, relations among words are made (I will not say "noticed"), and the notion of "go" becomes part of the notion of "went". Furthermore, the notion of a root meaning with tense modification becomes part of verbs in general. Again, I will not say that this is connected with any kind of symbolic rule. It may be the development of net nodes that are activated for root parts and for modifer parts of words. It would be overly rash to claim either that rules are involved or that they are not. In the final stage, the rule-like way of obtaining past tenses is well established enough that the exceptions can be clearly distinguished (whether statistically or otherwise is again disputable). One thing that seems perfectly clear is that humans are in general capable of inducing rules in the sense that some people can verbalize those rules. When such a person "teaches" a rule to a "student", the student must, initially at least, apply it AS a rule. But even in this case, it is not clear that skilled use of what has been learned involves continuing to use the rule AS a rule. It may have served to induce new node structures in a net. In "The Psychology of Reading" (Academic Press, 1983), my wife and I discussed such a sequence under the heading of "Three-phased Learning", which we took to be a fairly general pattern in the learning of skilled behaviour (such as reading). Phase 1 is the learning of large-scale unique patterns. Phase 2 is the discovery of consistent sub-patterns and consistent ways in which the sub-patterns relate to each other (induction or acquisition of rules). Phase 3 is the incorporation of these sub-elements and relational patterns into newly structured global patterns--the acquisition of true skill. "Theft," in Harnad's terms, can occur only as part of Phase 2. Both Phase 1 and Phase 3 involve "honest toil." My feeling is that current connectionist models are mainly appropriate to Phase 1, and that symbolic approaches are mainly appropriate to Phase 2, though there is necessarily overlap. There should not be a contention among models using one or other approach, if this is so. They are both correct, but under different circumstances. -- Martin Taylor DCIEM, Box 2000, Downsview, Ontario, Canada M3M 3B9 uunet!mnetor!dciem!client1!mmt or mmt@zorac.arpa (416) 635-2048