The Logical Problem

Lecture 8

Logical Problem

7 pillars of UG

1. The Logical Problem2. Centrality of recursion - LND3. Language organ and modularity4. Critical periods5. Grammar gene6. Sudden evolution of language7. Speech is special

Logical Problem

7 Pillars of Emergentism

1. Learning on input (today’s talk)

2. Emergence of recursion (also today)

3. Modules are made not born (Rethinking)

4. L1-L2 competition (TICS article)

5. Polygenic emergent genome

6. Gradual evolution (MacWhinney 2004)

7. Speech relies on mammalian abilities

Logical Problem4

Will they stand?

Logical Problem

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.

Logical Problem

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

Logical Problem

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

Logical Problem

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, …

Logical Problem

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….”

Logical Problem10

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

Logical Problem

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”

Logical Problem

Structural Dependency

1. The man who is next in line is coming.

2. Is the man who _ next in line is coming?

3. Is the man who is next in line _ coming?• This only applies to non-parameterized

aspects of language, since parameter setting requires positive evidence

Logical Problem13

GraphicallyGraphically

• The boy who is smoking is crazy.• Is the boy who smoking is crazy?

S

NP VP

the boy

who is smoking

crazyis

Logical Problem

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

Logical Problem

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?

Logical Problem

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?

Logical Problem

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.

Logical Problem

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.

Logical Problem

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?

Logical Problem

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

Logical Problem21

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.

Logical Problem

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

Logical Problem

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.

Logical Problem

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.

Logical Problem

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”

Logical Problem

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

Logical Problem

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

Logical Problem

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

Logical Problem

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

Logical Problem30

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.

Logical Problem

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 ___ ?

Logical Problem

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)

Logical Problem

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.

Logical Problem

Binding conditions

• Devilliers, Roeper, and Vainikka 19901. When did the boy say he hurt himself?

2. When did the boy say how he hurt himself?

3. 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.

Logical Problem

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.

Logical Problem

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.

Logical Problem

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

Logical Problem

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)

Logical Problem

Recovery from Overgeneralization

• u-shaped curve: went - goed - went• child must stop saying:

“goed” “unsqueeze” “deliver the library the book”

Logical Problem

An overly general grammar

correct grammar overly general

grammar

Logical Problem

For example

went

jumped

goed

runned

falled

wented

Logical Problem

Feedback must be consistent

Feedback No Feedback

Error Hit MissCorrect False

alarmCorrect

rejectionHigh signal detection (d-prime) maximizes p(hit)/p(FA)

Hits close to 1.0 and FA close to 0.0

Logical Problem

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

Logical Problem44

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.

Logical Problem

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

Logical Problem

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

Logical Problem

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 _ ?

Logical Problem

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 ___?

Logical Problem

2. Indirect Negative Evidence

• Lasnik, Chomsky, Braine, Berwick, Siskind

average frequency of V = frequency of “go”average frequency of V-ed frequency of “goed”

x = x’y y’

• If x/y < x’/y’ by a large amount

• and if y is frequent, then y’ must be incorrect

Logical Problem

Indirect Negative Evidence (cont.)

• do undotie untiezip unzip

squeeze (unsqueeze)

Logical Problem

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?

Logical Problem

3. Probabilism

• Horning (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.

Logical Problem

4. Competition

meaning

word word

competition

episodic

support

analogic

pressure

Logical Problem

Competition - example

go + PAST

went go + ed

competition

episodic

support

analogic

pressure

Logical Problem

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

Logical Problem

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.

Logical Problem57

Donating the library the book

Dative Role

to ___competition

“to”

episodic

supportextensional

pressure

V + NP + NP

verb

episodic

support

Logical Problem

Competition - complex

"pour arg1 arg2 arg3 "

"1 pours 2 into 3" "1 pours 3 with 2"

competition

lexical frame group frame:

1 verbs 3 with 2

group frame:

1 verbs 2 into 3

Logical Problem

Competition - semantic

demitassse cupcompetition

episodicsupport

extensionalpressure

Logical Problem

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

Logical Problem

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.

Logical Problem

5. Recovery Mechanisms

• Cue Construction (why you can’t donate the library the book)

• Monitoring (getting clearer episodic encoding)

• Paying attention to negative evidence

Logical Problem

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

Logical Problem

URLs

• childes.psy.cmu.edu• psyling.psy.cmu.edu• talkbank.org