The logical problem of language acquisition

1. The logical problemof language acquisition Brian MacWhinney CMU

2. Three views Socialization Theory Language is learned from interactions Connectionist Theory Language is learned from cues Nativist Theory Language is innate

3. The “facts” Child: Nobody don’t like me. Mother: No, say “Nobody likes me.” Child: Nobody don’t like me. Mother: No, say “Nobody likes me.” Child: Nobody don’t like me. Mother: No, say “Nobody likes me.” Child: Nobody don’t like me. [dialogue repeated five more times] Mother: Now listen carefully, say “Nobody likes me.” Child: Oh! Nobody don’t likeS me. (McNeill, 1966)

4. Brown and Hanlon (1970) parents correct for meaning not form when present, correction was not picked up

5. The intuitive problem The child makes an error. The adult may correct or identify the error. But the child ignores these corrections. So, how does the child learn to stop making the error?

6. Recovery from Overgeneralization u-shaped curve: went - goed - went child must stop saying: “goed” “unsqueeze” “deliver the library the book”

7. Noisy input Incomplete input Ignoring correction Not enough feedback Unclear referentially (Quine’s Problem) LPLA #1: Argument from Poverty of Stimulus

8. The Gold Proof

9. An overly general grammar

11. How to get the wrong grammar FG1 generates: ABD, AC (2) Provide ACD as positive data

12. 3. Adding an arc yields FG2

13. If we only have plain and simpleFINITE grammars like FG1 and FG2, information presentation is enough.

14. But, if the possible human languages include NONFINITE grammars like NFG1

15. NFG1 also generates *ACBD And ACBD is ungrammatical. But Informant presentation doesn’t tell us this. So… we will never be able to give up NFG1 and go back to FG1 or FG2. So…We will never learn the correct language without corrective feedback.

16. Input must be really consistent

17. d-prime maximizes this ratio:____hits____false alarms p (Error|Signal) must be close to 1.0.p (Correct|Signal) must be close to 0.0.

18. But, sometimes adults say “no” when a sentence is correct. This means that p(Correct|Signal) is not close enough to 0.0to learn on a few examples.SO, child will need LOTS of examples if he tries to learn through Signal Detection.

19. But ….If a parent were to provide true negative evidence of the type specified by Gold, interactions would look like this: Child: me want more. Father: ungrammatical. Child: want more milk. Father: ungrammatical. Child: more milk ! Father: ungrammatical. Child: cries Father: ungrammatical

20. Contrast with this interaction: Child: me want more. Father: You want more? More what? Child: want more milk. Father: You want more milk? Child: more milk ! Father: Sure, honey, I’ll get you some more. Child: cries Father: Now, don’t cry, daddy is getting you some.

21. Snow, Bohannon, Farrar, Hirsh-Pasek, Cross, Sokolov, MacWhinney, Keith Nelson, and many others: 1. Correction is targeted. Only simple, clear errors are corrected. 2. Input is targeted by developmental level. Fine-tuning 3. Pickup may be on the next page of the transcript. 4. Child can process: overt correction, recasts, restatements, clarification questions, “What?” “huh?” continent queries, Some combination of these cues? 5. Experiments have shown that correction works.

22. BUT For the sake of analysis, let us grant thatCorrective feedback is  not available, and if available is not used, and if used is not effectiveThere are 5 potential solutions to LPLA#1

23. 1. Simple Blocking -- Baker

24. 2. Conservatism Conservative child learners only use forms they have heard adults use. Logically, the constraint of conservatism would work, but overgeneralizations prove that learners are not conservative. If children waited until each form were confirmed, they would never say  *goed *unsqueeze *deliver the library the book They would never overgeneralize. But they do and so do L2 learners. Conservatism can explain obedience to principles

27. 3. Indirect negative evidenceLasnik, Chomsky, Braine, Berwick, Siskindaverage frequency of V = frequency of “go”average frequency of V-ed frequency of “goed” x = x’ y y’

28. If x’/y’ > x/y by a large amountand if y is frequentThen Y’ is blocked. do undo tie untie zip unzipsqueeze (unsqueeze)

29. Using Indirect Neg Evidence N in relative = N in complement N extracted N extracted Bill thought the thieves were carrying the loot. What did Bill think the thieves were carrying. The police arrested the thieves who were carrying the loot. * What did the police arrest the thieves who were carrying?

30. 4. ProbabilismHorning (1969) shows that Gold’s Proof fails for probabilistic grammars.These can be identified on positive evidence alone.Labov’s variable rules are a good example of probabilistic grammars.

31. 5. Competition generator -- rules blocker -- constraints generator -- analogic pressure blocker -- episodic support

34. Single trial learning to criterion will not occur when analogic pressure is strong.

36. EPISODES are specific encounters with particular form-function relationsEXTENSIONAL PRESSURE is based on patterns involving multiple exemplars. Morphological extension is to a new stem.Semantic extension is to a new referent.

37. Modeling analogic pressure

38. Recovery from Overgeneralization 1. Rote learning through episodic support Emergence of “went” 2. Growth of generalization through extensional pressure Occasional use of “goed” 3. Competition between pathways “went” competes with “goed” 4. Processing: “went” is slower than “goed” (Kawamoto, 1993) expressive monitoring (MacWhinney, 1978) adaptive resonant connections strengthen “went” (Grossberg, 1987)

39. LPLA #2: Non-occurring errors Chomsky: “recent advances” make the logical problem trivial, since there occuring is so little left to learn Problems: No system of triggers has been identified No rules for the interaction of triggers with data is available No agreement on parameter interactions has been reached For these reasons, few have accepted Chomsky’s analysis.

40. Structural Dependency The man who is first in line is coming. Is the man who __ first in line is coming? Is the man who is first in line ___ coming? This only applies to non-parameterized aspects of language.

41. No need for positive evidence Chomsky: “A person might go through much or all of his life without ever having been exposed to relevant evidence, but he will nevertheless unerringly employ the structure-dependent generalization, on the first relevant occasion.” Hornstein and Lightfoot “People attain knowledge of the structure of their language for which no evidence is available in the data to which they are exposed as children.”

42. Emergentist solution Item-based learning for aux Movement formulated in terms of relations, not position (this is the crucial step) Competition yields construction (not needed initially, but part of general solution) As a result (3) is produced instead of (2)

43. More cases *Who did John believe the man that kissed ___ arrived? Who did John believe __ kissed his buddy? *What did you stand between the wall and __? *What did you see a happy ___?

44. General Issue Conservatism Parsing Competition from Alternative (in situ) Impossible Meaning Universal Constraints