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The Logical Problem. Lecture 8. 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. 7 Pillars of Emergentism. Learning on input (today’s talk)

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7 pillars of ug
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
7 pillars of emergentism
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
are packages monoliths
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.
pillar 1 chomsky 1980
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
the input is not degenerate
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
two arguments
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, …
no need for positive evidence
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….”
motivating ug
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
power of appe
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”
structural dependency
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
graphically
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?
constraints
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
what counts as positive evidence
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?
the input
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?
evidence from childes
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.
no evidence no production
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.
experimental evidence
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?
two other major sources
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
the biggest source
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.
item based learning
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
yes it is structural
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.
yes it involves recursion
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.
but what is recursion
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”
is recursion special
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
evidence for ug
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
more on appe kimball 1973
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
but a childes search found
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
slide30
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.
complex np constraint
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 ___ ?
data from seth 3 4
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)
is this error free learning
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.
binding conditions
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.
perhaps but
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.
slide36
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.
correction is available
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
but feedback is often ignored
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)
recovery from overgeneralization
Recovery from Overgeneralization
  • u-shaped curve: went - goed - went
  • child must stop saying:
    • “goed”
    • “unsqueeze”
    • “deliver the library the book”
feedback must be consistent
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

but it is not
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
grammar may not matter
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.
so let us grant
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
1 conservatism
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
conservativism cont
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 _ ?
conservativism cont1
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 ___?
2 indirect negative evidence
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
indirect negative evidence cont
Indirect Negative Evidence (cont.)
  • do undo tie untie zip unzipsqueeze (unsqueeze)
indirect negative evidence cont1
Indirect Negative Evidence (cont.)
  • 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?
3 probabilism
3. Probabilism
  • Horning (1969) shows thatGold’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.
competition
Competition
  • Other names for competition
    • Blocking -- Baker 1970
    • Uniqueness -- Pinker 1984
    • Mutual exclusivity -- Markman 1986
    • Semantic mapping -- Anderson 1978
  • Competition includes conservatism, probabilism, and indirect neg evidence
verb classes and overgeneralization
Verb classes and overgeneralization
  • Pour the water into the tub.
  • Fill the tub with water.
  • *Pour the tub with water.
  • *Fill the water into the tub.
competition definitions
Competition - definitions
  • EPISODES are specific encounters with particular form-function relations
  • EXTENSIONAL PRESSURE is based on patterns involving multiple exemplars.
  • Morphological extension is to a new stem.
  • Semantic extension is to a new referent
competition as the oracle
Competition as the Oracle
  • Competition provides negative evidence. The child internalizes the adult who is now the Oracle.
  • This solves Gold’s Problem, since there is now internal negative evidence.
5 recovery mechanisms
5. Recovery Mechanisms
  • Cue Construction (why you can’t donate the library the book)
  • Monitoring (getting clearer episodic encoding)
  • Paying attention to negative evidence
conclusions
Conclusions
  • The APPE is wrong, but there are low-error constructions.
  • The APNE is wrong, but some overgeneralizations are hard to correct.
  • Language learning is multiply buffered and emergent.
  • Pillar #1 is collapsing.
  • Maybe it is time to look at CHILDES and not (just) the WSJ
slide64
URLs
  • childes.psy.cmu.edu
  • psyling.psy.cmu.edu
  • talkbank.org