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Date 15.08.2008
Bidirectional OT and language acquisition
Petra Hendriks
ESSLLI 2008 course “Bidirectional OT in natural language”Hamburg, August 15, 2008
Date 15.08.2008
>The elephant is hitting himself.Children: NO
>The elephant is hitting him.Children: YES
>Here is an elephant and an alligator.
>The elephant is hitting himself.Children: YES
>The elephant is hitting him.Children: YES
Comprehension
Date 15.08.2008
Production/comprehension asymmetry:
>Pronoun Interpretation Problem (e.g., Jakubowicz, 1984; Chien & Wexler, 1990; Grimshaw & Rosen, 1990, for English; Deutsch, Koster & Koster, 1986; Koster, 1993; Philip & Coopmans, 1986, for Dutch)
The elephanti is hitting himi/j
Until 6-7 years old
>However, children’s production is adult-like from age 4 on!(de Villiers, Cahillane & Altreuter, 2006, for English; Spenader, Smits & Hendriks, in press, for Dutch)
Puzzle
Date 15.08.2008
>Children: The elephant is hitting him/the alligator.
>Cf. adults
>Children: The elephant is hitting himself.
>Cf. adults
(Spenader, Smits & Hendriks, in press)
Production
Date 15.08.2008
Binding Theory (Chomsky, 1981):>Principle A: A reflexive must be bound in its
local domain.>Principle B: A pronoun must be free in its
local domain.
How can comprehension of pronouns be delayed, while production of pronouns is adult-like?
Binding Theory
Date 15.08.2008
Explanations of PIP: Children possess the linguistic knowledge, but make errors due to:
>Lack of relevant pragmatic knowledge(e.g., Chien & Wexler, 1990; Thornton & Wexler, 1999)
>Interference of task factors(e.g., Bloom, Barss, Nicol & Conway, 1994; Grimshaw & Rosen, 1990)
>Lack of sufficient processing resources(e.g., Avrutin, 1999; Reinhart, 2006)
Explanations
Date 15.08.2008
If the Pronoun Interpretation Problem lies outside the grammar:
>Why is production unaffected?>Why does the PIP not arise in all languages?>Why does the PIP not arise in all constructions
in a language?
Aim of this talk: Investigate the hypothesis that the PIP (and other asymmetries) can be explained from the grammar itself.
Aim
Date 15.08.2008
Outline: The grammar: Optimality Theory Constraint reranking OT is a direction-sensitive grammar Production/comprehension asymmetries Bidirectional OT results in a symmetric
system Predicting further asymmetries in acquisition
(e.g., PIP, subject anaphora)
Outline
Date 15.08.2008
Markedness constraints, e.g.: NoCoda: No syllables with a coda. *Dors: No dorsal segments.
Faithfulness constraints, e.g.: Parse: No unparsed underlying material. Fill: No insertion of new material.
Optimality Theory
Date 15.08.2008
Input:
/kæt/
FAITH
(Parse, Fill)
MARK
(NoCoda, *Dors)
[kæt] *
[ta] *!
Tableau 1Adults’ grammar:FAITH >> MARK
Input:
/kæt/
MARK
(NoCoda, *Dors)
FAITH
(Parse, Fill)
[kæt] *!
[ta] *
Tableau 2Children’s grammar:MARK >> FAITH
Language acquisition involves constraint reranking:
Constraint reranking
Date 15.08.2008
Input:
/kæt/
MARK
(NoCoda, *Dors)
FAITH
(Parse, Fill)
[kæt] *!
[ta] *
Tableau 2Children’s grammar:Production
Input:
[kæt]
MARK
(NoCoda, *Dors)
FAITH
(Parse, Fill)
/kæt/
/hæt/ *!
Tableau 3Children’s grammar:Comprehension
Production and comprehension yield different results:
Smolensky (1996)
Date 15.08.2008
>Optimality Theory is output-oriented: Markedness constraints penalize outputs Faithfulness constraints penalize input-output
mappings
>If the direction of optimization is reversed, this affects the application of markedness constraints (but not faithfulness constraints).
Output-oriented
Date 15.08.2008
>Production: Meaning form Faithfulness constraints Markedness constraints on form
>Comprehension: Form meaning Faithfulness constraints Markedness constraints on meaning
>Because different constraints apply in the two directions of optimization, OT is direction-sensitive.
Direction-sensitive
Date 15.08.2008
So there is evidence for early delays in production. Do we find similar delays in comprehension?
Yes, if Chapman & Miller (1975) are right in that production precedes comprehension w.r.t. early word order.
>The car is pulling the cow.
Comprehension delay?
Date 15.08.2008
>Q: Does the adult constraint ranking always result in the same pairing of form and meaning in production and comprehension?
>A: This depends on the constraints. Particular combinations of constraints give rise to a different pairing in production and comprehension.
Example: Object pronouns
(A)symmetry
Date 15.08.2008
>Principle A (FAITH):No reflexives with a locally disjoint meaning.
>Referential Economy (MARK):No full NPs >> No pronouns >> No reflexives
(Principle B need not be assumed, but rather is a derived effect)
Pronouns
Date 15.08.2008
Input:
coref.
FAITH
Principle A
MARK
Ref Econ
reflexive
pronoun *!
Tableau 4Production of coreferential meaning
Input:
disjoint
FAITH
Principle A
MARK
Ref Econ
reflexive *!
pronoun *
Tableau 5Production of disjoint meaning
Production yields the adult forms:
Production
Date 15.08.2008
Input:
reflexive
FAITH
Principle A
MARK
Ref Econ
coref.
disjoint *!
Tableau 6Comprehension of reflexive
Input:
pronoun
FAITH
Principle A
MARK
Ref Econ
coref.
disjoint
Tableau 7Comprehension of pronoun
But comprehension results in a non-adult pattern:
Comprehension
Date 15.08.2008
This is exactly children’s pattern w.r.t. the Pronoun Interpretation Problem.
>Q: But why aren’t pronouns ambiguous for adults?
>A: Because adults optimize bidirectionally, whereas children are not yet able to do so. (de Hoop & Krämer, 2005/6; Hendriks & Spenader, 2005/6; Hendriks et al., Conflicts in interpretation)
Ambiguity
Date 15.08.2008
Bidirectional optimization (Blutner, 2000):
A form-meaning pair <f,m> is bidirectionally optimal iff:
a.there is no other bidirectionally optimal pair <f’,m> such that <f’,m> is more harmonic than <f,m>.
b.there is no other bidirectionally optimal pair <f,m’> such that <f,m’> is more harmonic than <f,m>.
Blutner (2000)
Date 15.08.2008
FAITH
Principle A
MARK
Ref Econ
<reflexive, coref.>
<reflexive, disjoint> *
<pronoun, coref.> *
<pronoun, disjoint> *
Tableau 8Bidirectional optimization of anaphoric objects
Principle B
A symmetric system arises through bidirectional optimization:
Bidirectional OT
Date 15.08.2008
Language acquisition in bidirectional OT:
>Initial constraint ranking (presumably MARK >> FAITH)
>Error-driven constraint reranking (e.g., Tesar & Smolensky, 1998; Boersma & Hayes, 2001)
>Adult constraint ranking>From unidirectional to bidirectional
optimization
Language acquisition
Date 15.08.2008
How can we decide between biOT explanation and alternative accounts?
>Alternative accounts predict that production in general is relatively easy.
Example: Subject pronouns
Bidirectional OT
Date 15.08.2008
Him
Ladies and gentlemen, we got him!
Paul Bremer at press conference in Baghdad, 14 Dec. 2003
Date 15.08.2008
Pronouns refer to very salient referents, usually mentioned in the linguistic discourse.
>ProTop (FAITH): No pronouns that refer to a non-topic.
Topic
Date 15.08.2008
MARK
Ref Econ
FAITH
Pro Top
<pronoun, +topic>
<pronoun, -topic> *
<full NP, +topic> *
<full NP, -topic> *
Tableau 9Bidirectional optimization of anaphoric subjects
The adult pattern can be modeled by bidirectional optimization:
Recoverability
Date 15.08.2008
Input:
+topic
MARK
Ref Econ
FAITH
Pro Top
pronoun
full NP *!
Tableau 10Production of topical referent
Input:
-topic
MARK
Ref Econ
FAITH
Pro Top
pronoun *
full NP *!
Tableau 11Production of non-topical referent
Predictions with respect to production:
Predictions
Date 15.08.2008
Input:
pronoun
MARK
Ref Econ
FAITH
Pro Top
+topic
-topic *!
Tableau 12Comprehension of pronoun
Input:
full NP
MARK
Ref Econ
FAITH
Pro Top
+topic
-topic
Tableau 13Comprehension of full NP
Predictions with respect to comprehension:
Predictions
Date 15.08.2008
>If children are unable to optimize bidirectionally, it is predicted that: They overuse pronouns to refer to non-
topics. They fail to interpret full NPs as marking a
topic shift.>This was tested in a production/
comprehension experiment with 4- to 6-year-old Dutch children. (Wubs, Hendriks, Hoeks & Koster, to be presented at GALANA 3)
Experiment
Date 15.08.2008
Date 15.08.2008
A pirate is walking with a ball.
He kicks away the ball.
But then the ball falls into the water and he starts to cry.
A knight arrives with a fishing net.
He scoops the ball out of the water.
And then the pirate has his ball back again.
Date 15.08.2008
4
37
59
0
20
40
60
80
100
Pronoun Full NP Other
0
97
3
0
20
40
60
80
100
Pronoun Full NP Other% p
rod
uce
d f
orm
s
Children (4-6 y.o.) Adults
Production of referring expression to refer to old topic after topic shift
Results
Date 15.08.2008
Adults: >And then the pirate has his ball back again.
Many children: >And then he has his ball back again.
By using a non-recoverable pronoun, children as speakers do not take into account the hearer.
This suggests lack of bidirectional optimization.
Egocentric
Date 15.08.2008
Input:
pronoun
FAITH
Principle A
MARK
Ref Econ
FAITH
Pro Top
coref. &-topic
*!
disjoint & +topic
Tableau 14Comprehension of pronoun
Prediction: Pronoun Interpretation Problem disappears if there is a clearly established topic.
Another prediction
PIP dissolves entirely in single topic context:
“Here is an alligator. The elephant is hitting him”
Spenader, Smits & Hendriks, in press
Date 15.08.2008
Young children(<4 years old)
Older children(>4 years old)
Delay in production
First words Anaphoric subjects
Delay in comprehension
Early word order?
Pronoun Interpretation Problem
Asymmetries
Bidirectional OT predicts four types of asymmetries:
Date 15.08.2008
How does bidirectional optimization develop?
>Blutner & Zeevat (2004): Pragmatic reasoning about form-meaning pairs that can become conventionalized
>Hendriks, van Rijn & Valkenier (2007): Online mechanism, dependent on processing resources: Form meaning form Meaning form meaning
Development
Date 15.08.2008
Do processing resources matter? YES>Also overuse of subject pronouns by elderly
adults (>60 years old).(Hendriks, Englert, Wubs & Hoeks, 2008)
>Overuse of subject pronouns appears to be related to working memory capacity.(Wubs, Hendriks, Hoeks & Koster, to be presented at GALANA 3)
>Children’s comprehension of object pronouns improves when speech is slowed down.(Van Rij-Tange, Hendriks, Spenader & Van Rijn, to be presented at GALANA 3 & BUCLD 33)
Processing
Date 15.08.2008
Can the data also be explained by extra-grammatical factors?
>Pragmatic knowledge: Separate explanation required for each phenomenon
>Task factors: Methodological pessimism>Processing limitations: May account for late
asymmetries, but weaker explanation
Other explanations
Date 15.08.2008
Testing theories
Date 15.08.2008
Because OT is direction-sensitive, it allows for a straightforward explanation of production/comprehension asymmetries in language acquisition:
>Early asymmetries can be explained as the result of a non-adult constraint ranking.
>Late asymmetries can be explained as the result of the inability to optimize bidirectionally.
Conclusions
