The Logical Problem

1. The Logical Problem • Lecture 8

2. 7 pillars of UG • The Logical Problem • Centrality of recursion - LND • Language organ and modularity • Critical periods • Grammar gene • Sudden evolution of language • Speech is special

3. 7 Pillars of Emergentism • Learning on input (today’s talk) • Emergence of recursion (also today) • Modules are made not born (Rethinking) • L1-L2 competition (TICS article) • Polygenic emergent genome • Gradual evolution (MacWhinney 2004) • Speech relies on mammalian abilities

4. Will they stand?

5. Are packages monoliths? • One pillar could crumble and the building would not fall. • But, the more the pillars the stronger the edifice. • In practice, there are subgroups that subscribe to different collections of pillars. • Research must analyze one pillar at a time.

6. Pillar #1: Chomsky (1980) • The child’s acquisition of language is “hopelessly underdetermined by the fragmentary evidence available.” • Degeneracy of input • Lack of positive evidence • Lack of negative evidence

7. The Input is not Degenerate • Newport, Gleitman, and Gleitman (1977) showed that mothers speak grammatically • Sagae, MacWhinney, and Lavie have shown that the input in the CHILDES database is as parsable as the Wall Street Journal

8. Two Arguments • Argument from Poverty of Negative Evidence (APNE) • Lack of correction • Rejection of correction • Gold’s proof • Recovery from overgeneralization • Argument from Poverty of Positive Evidence (APPE) • Absence of input • Weakness of learning mechanisms • Degeneracy, incommensurability, …

9. No need for positive evidence • Chomsky 1980: “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 1987 “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.” • Crain 1991 “...every child comes to know facts about the language for which there is no decisive evidence from the environment. In some cases, there appears to be no evidence at all….”

10. Motivating UG • It is, for the present, impossible to formulate an assumption about initial, innate structure rich enough to account for the fact that grammatical knowledge is attained on the basis of the evidence available to the learner. Consequently, the empiricist effort to show how the assumptions about a language acquisition device can be reduced to a conceptual minimum is quite misplaced. The real problem is that of developing a hypothesis about initial structure that is sufficiently rich to account for acquisition of language, yet not so rich as to be inconsistent with the known diversity of language. -- Chomsky 1965

11. Power of APPE • No need to discuss negative feedback • Relies simply on facts about input corpus • Constraints can be demonstrated experimentally by providing sentences that were “never heard”

12. Structural Dependency • The man who is next in line is coming. • Is the man who _ next in line is coming? • Is the man who is next in line _ coming? • This only applies to non-parameterized aspects of language, since parameter setting requires positive evidence

13. Graphically S VP NP crazy is the boy who is smoking Graphically • The boy who is smoking is crazy. • Is the boy who smoking is crazy?

14. Constraints • The AUX of the relative clause must move from INFL across the CP and COMP of the relative clause (around “man”) • But the Head Movement Constraint (HMC) blocks this. Ross (1969) • No such barriers exist in the main clause • Also, movement of AUX would leave a gap that violates the Empty Category Principle (ECP) in the relative clause

15. What counts as positive evidence? • Same AUX type • Is the man who is next in line coming? • Different AUX type • Will the man who is next in line _ come? • Item-based or class-based?

16. The Input • Pullum and Scholz (2002) found that 1% of the Wall Street Journal (WSJ) corpus has positive evidence. Most is of the different AUX type. So there is a huge amount of positive input. Or is there?

17. Evidence from CHILDES • A search of the English CHILDES database (3 million utterances) by Lewis and Elman (2001) found only one utterance in the input to Adam. • MacWhinney also found one in the input in the Hall corpus.

18. No evidence, no production • So there is no positive evidence of this type. • But there is also no production, so how can we know that children follow the constraint.

19. Experimental Evidence • Crain and Nakayama (1987): Ask Jabba if the boy who is watching Mickey is happy? • Children (3-5) never moved the AUX of the relative, although they did other strange things • But the procedure gives the children the relative as a frozen unit. • “the boy who is watching Mickey” • There is a fundamental pragmatic fact about relative clause freezing that the structural analyses are ignoring, but … • Still, let us grant that children have some sense of this constraint by age 4. Is there really no input?

20. Two other major sources • Double AUX, Sub, WH • Which is the dog that is clawing at the door? • There are dozens of sentences of this type in the database. • They show the relative clause staying intact. • Elman and Lewis’s parser hates: the dog that clawing • Single AUX, Sub, WH • Where is the dog that you like? • There are hundreds of these. • They also illustrate keeping the subordinate clause frozen

21. The biggest source • You can learn from just main clauses • Is the baby happy? • Lightfoot (1986, 1997) degree-zero learnability • Main clause movement is demonstrated. • Sub clause movement is not illustrated. • Conservatism: If something is not illustrated, it is not legal.

22. Item-based learning • Item-based learning for AUX (will, is, can) • Is the dog coming? is + (NP) + V • Can you come? can + (NP) + V • Item-based learning for COP • Is Billy your friend? Is + (NP) + PredN • Was he your friend? Was + (NP) + PredN • Eventual emergence of class-based patterns • AUX + (NP) + V • COPY + (NP) + NP

23. Yes, it is Structural • Movement formulated in terms of valency relations (GRs), not position (crucial assumption). • Single AUX sentences teach the basic pattern. • Double AUX sentences show that the choice must be based on the AUX - V valency relation. • For WH, the rule is WH - AUX - (NP) - V.

24. Yes, it involves Recursion • MacWhinney (1982, 1987) emphasizes the fact that heads in valency relations (item-based patterns) can themselves be complex clusters. • Word clusters implement recursion. • Here, the whole relative clause is an NP which is not a part of the AUX + (NP) + V pattern that is learned.

25. But, what is Recursion? • Clustering produces embeddings and X-bar • Psychological minimum is • Head clustering (in a buffer or memory) • Repeated application to clustered heads • But, this probably operates in real time from “left to right”

26. Is Recursion Special? • Do we cluster in space? • Getting from Pittsburgh to ACL • Climbing Stenhuten and reversing my path • These use goal stacks and no words • Working on an engine involves hierarchical decomposition of parts without words • Biederman’s geons constitute a hierarchical system

27. Evidence for UG? • The APPE fails -- there is positive evidence. • Learning is item-based and the structure is emergent. • So, yes, parsing depends on structure, but not on UG • So, this half of the pillar does not support UG

28. More on APPE - Kimball 1973 • Kids hear • It rains. • It may rain. • It may have rained. • It may be raining. • But never • It may have been raining. • So, there is no positive evidence

29. But a CHILDES search found • 27 might have been • 5 may have been • 24 could have been • 15 should have been • 70 would have been

30. So ... • We can learn: modal + “have_been” • There is really no shortage of positive evidence on this. • Kimball’s mistake was to only search for “may have been” since there were only 5 of these. • Again, learning mechanisms have to be given a little bit of power. We have to allow for extraction of IBPs and then FBPs, along with clustering.

31. Complex-NP Constraint • Who did John believe __ kissed his buddy? • * Who did John believe the man that kissed __ arrived • * Who did pictures of ___ surprise you? • * What did you see a happy ___ ? • * What did you stand between the wall and ___ ?

32. Data from Seth (3-4) • What am I cooking on a hot __ ? (stove) • What are we gonna look for some __ ? (houses) • What is this a funny __ , Dad? • What are we gonna push number __ ? (9) • Where did you pin this on my __ ? (robe) • What are you shaking all the __ ? (batter and milk) • What is this medicine for my __ ? (cold)

33. Is this error-free learning? • There are definitely errors. • There is definitely positive evidence. • But it is true that errors seem to be relatively scarce. • So, this is “low error” learning. • We will return to this later.

34. Binding conditions • Devilliers, Roeper, and Vainikka 1990 • When did the boy say he hurt himself? • When did the boy say how he hurt himself? • Who did the boy ask what to throw? • Young children can’t understand #3. • Children will associate “when” with “hurt” in #1 more than #2, but this understanding grows with age • Therefore binding seems to be learned.

35. Perhaps … But … • Perhaps De Villiers et al. are saying that what is UG is the ability to identify and utilize the structure. • Perhaps learning is just a matter of identifying triggers (Sakas, Buttery) • But the relevant structural details can be expressed in terms of grammatical relations and IBPs.

36. APNE • Failure of the APPE does not remove the APNE. • APNE provides evidence for a “gyroscope” steering the child away from the shoals of error. • Thus, there could be evidence that language is constrained by UG, even if positive evidence is available.

37. Correction is available • Parents provide targeted correction for identificable errors • Bohannon and Stanowicz, Nelson, Farrar, Cross • Fine-tuning • Sokolov and Snow, Sokolov and MacWhinney • Error feedback may be delayed • Brown and Hanlon

38. But feedback is often ignored • 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)

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

40. An overly general grammar

41. For example

42. Feedback must be consistent High signal detection (d-prime) maximizes p(hit)/p(FA) Hits close to 1.0 and FA close to 0.0

43. But it is not • Sometimes adults say “no” when a sentence is correct • Unless kids have extremely clear ability to distinguish types of “no” they will be confused • So, direct reliance on provision of corrective feedback may not be such a great strategy

44. Grammar may not matter • Brown & Hanlon (1970): • Adults understood 42% of the grammatical sentences. • Adults understood 47% of the ungrammatical ones. • Adults expressed approval after 45% of thegrammatical sentences. • Adults expressed approval after 45% of the ungrammatical sentences.

45. So, let us grant • Corrective feedback is often not available. • If available, it is not consistent. • Even if consistent, it may be ignored. • But there are still five solutions to the APNE form of the logical problem

46. 1. Conservatism • Conservative child learners only use forms they have heard adults use. • Logically, the constraint of conservatism (Subset Principle) would work, but overgeneralizations prove that learners are not conservative. • Item-based learning implements conservativism, but it gives way to pattern-based learning

47. Conservativism (cont.) • Who hit the little girl with the block today? • Who did the little girl hit _ with the block today? • Who did the boy play with _ behind his mother? • Who did the boy read a story about _ ? • Child never hears: Who do the boy read a story that described _ ?

48. Conservativism (cont.) • *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 ___?

49. 2. Indirect Negative Evidence • Lasnik, Chomsky, Braine, Berwick, Siskindaverage frequency of V = frequency of “go”average frequency of V-ed frequency of “goed”x = x’yy’ • If x/y < x’/y’ by a large amount • and if y is frequent, then y’ must be incorrect

50. Indirect Negative Evidence (cont.) • do undo tie untie zip unzipsqueeze (unsqueeze)