Transcript Slide 1

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Optimality-Theoretic Pragmatics
Meets Experimental Pragmatics
Experimental Pragmatics Conference,
Humboldt University, Berlin, December 14-16, 2007
Reinhard Blutner
http://www.blutner.de
[email protected]
Institute for Logic,
Language and Computation
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0 Introduction
“With four parameters I can fit an elephant, and with
five I can make him wiggle his trunk”
(John von Neumann)
as quoted by Freeman Dyson in "A meeting with Enrico Fermi"
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Grice and His Followers
NeoGricean
Theories
OT-Pragmatics
Relevance Theory
(Horn, Atlas)
Presumptive Meanings
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Experimental Pragmatics
“Properly devised experimental evidence can be
highly pertinent to the discussion of pragmatic issues,
and pragmatics might greatly benefit from becoming
familiar with relevant experimental work and from
contributing to it ”
(Noveck & Sperber 2007, p. 210)
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Optimality Theoretic Pragmatics
› Like generally in OT: no artificial boundary
between competence and performance
› Bidirectional grammar (constraint-based)
› NL comprehension as interpretive optimization
› NL production as expressive optimization
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Open Issues
› Are the two optimization processes integrated
with each other (bidirectional optimization)?
› How to explain the asymmetries between
comprehension and production?
› The role of fossilization/conventionalization?
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The Idea of Fossilization
› ‘Invited Inferences’ (Geis & Zwicky 1971). Mechanism
of conventionalization for implicatures
› Short-circuited implicatures (Morgan 1978; Horn &
Bayer 1984)
› Lexicalization (Cole 1975)
› Traugott (1989…2005) applied the idea to explain
language change
› Levinson (2000) und Mattausch (2004) used the
idea for explaining the development of binding.
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Outline
1.
Pronouns/Reflexives with children and adults
2.
R-expressions/Pronouns
elderly adults
3.
All/Some (Scalar Implicatures) with children
and adults
4.
Conclusions
with
young
and
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1 Pronouns/Reflexives
In an important recent article Hendriks and
Spenader (2004) give a new interpretation of
children‘s delay of the comprehension of
pronouns. I discuss the validity of this
interpretation and present an alternative
account in terms of iterated learning
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Children’s comprehension of reflexives*
› Here is an elephant and an alligator. The elephant is
hitting himself.
› Question: Does the sentence match the picture?
› Children from age 4 on: Yes
* I thank Petra Hendriks for allowing me to use her slides
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The pronoun interpretation problem
› Here is an elephant and an alligator. The elephant is
hitting him.
E.g., Chien & Wexler, 1990; Grimshaw
& Rosen, 1990; Jakubowicz, 1984;
Koster, 1993; McDaniel, Smith Cairns,
& Hsu, 1990; McDaniel & Maxfield,
1992; McKee, 1992.; Spenader, Smits &
Hendriks, subm.
› Question: Does the sentence match the picture?
› Children until at least the age of 6 or 7: Yes
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Children’s production of pronouns
› Task: Describe what you see on the picture.
Cf. De Villiers, Cahillane, & Altreuter, 2006;
Spenader, Smits, & Hendriks, subm.
The elephant is hitting him.
› Children between 4;6 and 7:
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Children’s production of reflexives
› Task: Describe what you see on the picture.
The elephant is hitting himself
› Children between 4;6 and 7:
*The elephant is hitting him
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Production/comprehension asymmetry
› Production results show that very young children
have competence of binding principles
› But if this is true, then why don’t they use this
knowledge in comprehension?
› Usually, comprehension of a given form precedes
production of this form (Bates, Dale and Thal 1995; Benedict 1979; Clark
1993; Fraser, Bellugi and Brown 1963; Goldin-Meadow, Seligman and Gelman 1976)
› How do we reconcile children’s poor performance on
comprehension tasks with their near-perfect
production data?
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1.1 Hendriks & Spenader‘s
Account
Hendriks’ and Spenader’s (2004) model
accounting for children‘s delay of the
comprehension of pronouns. The model
assumes delayed bidirection.
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Optimality Theory as a Framework
Input
Generator
Candidates
Contraint-Hierarchy:
C1 >> C2 >> C3
1
2
3
Evaluator
Output
4
5
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Unidirectional OT
› Consider two directions of optimization (Heareroriented, Speaker-oriented)
› Use the same set of constraints and the same
ranking for both perspectives
› Hence, the evaluator evaluates pairs of
representations (e.g. form-meaning pairs)
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Constraints
›
›
(slidely modifying Burzio 1998)
PRINCIPLE A: A reflexive must be bound locally
REFERENTIAL ECONOMY:
Avoid R-expressions >> Avoid pronouns >> Avoid reflexives
pro
pro
self
self
disj
conj
PRINCIPLE A
disj
conj
REFERENTIAL ECONOMY
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Assuming a Ranking
pro
self
disj
conj
pro
disj
self
conj
› PRINCIPLE A >> REFERENTIAL ECONOMY
› Hearer‘s perspective: one optimal interpretation for
self but two optimal interpretations for pro.
› Speaker‘s perspective: correct unique form for each
interpretation.
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Bidirectional OT
Strong bidirection = Consider both directions of
optimization simultaneously
pro
self
disj
conj
pro
disj
self
conj
When hearing a pronoun, a bidirectional actor reasons about what other non-expressed
forms the speaker could have used, compare the interpretation associated with the pronoun
and realize that a coreferential meaning is better expressed with a reflexive. Then, by a
process of elimination, she must realize the pronoun should be interpreted as disjoint.
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Delayed Bidirection
› The proposal is that children begin with unidirectional
optimization, and only later acquire the ability to
optimize bidirectionally.
› Optimizing bidirectionally inherently involves reasoning
about alternatives not present in the current situation,
which may be a skill acquired very late, thus explaining
the lag in acquisition.
› Optimizing bidirectionally requires more processing
resources than unidirectional optimization
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Advantages
› The authors are able to derive Principle B effects
from Principle A alone, through bidirectional
optimization.
› The analysis clearly distinguishes the task of a
speaker from the task of a hearer. As a result the
analysis is able to model different results for
production and comprehension.
› Besides the stipulation of the constraints and their
ranking no other stipulations are required
› The approach nicely combines a pragmatic
explanation with a processing account (lack of
processing resourses)
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Disadvantages
› The constraints are partly stipulated - no constraint
grounding
› Theory of Mind (Perner, Leekam and Wimmer 1987)
requires awareness of other conversation
participant’s choices. Hence, theory of mind is based
on controlled reflection rather than automatic
processing. However, the effects of pronoun
processing are nearly automatic. There is no explicit
hint for mind reading capacities in such tasks.
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1.2 A Model in Terms of
Learning/ Fossilization
Rather than stipulating a change from unidirectional to bidirectional processing I
account for the effects of bidirection by a
mechanism
of
learning/automatization
(changing the constraint ranking)
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Learning as Utility Optimization
› Learning consists in improving the value of expected
utility (measuring the success of communication)
› In OT-learning theories the ranking of a given system of
constraints is (stepwise) changed
› Learning leads to a stable outcome if the relevant EU(s)
reach its maximum value
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A Very Simple Learning Algorithm
m
Speaker
f
Hearer
m’
m = m’ ?
If yes, nothing happens
If no, adjustment:
All constraints that favour (f, m) over (f, m’) are promoted
All constraints that favour (f, m’) over (f, m) are demoted
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Application: Fossilization
pro
self
disj
›
conj
›
›
disj
conj
pro
disj
self
conj
Speaker
Hearer
Principle A: self
 conjoint
self
conj nothing happens
Referential Economy: self >> pro
Hearer
Speaker
Principle B: pro  disjoint; …. nothing happens
disj
pro
conj constraint B strengthened
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Conclusion: Two models
› Processing account (unidirectional versus
bidirectional processing)
› Fossilization account (applying OT learning
theory). This view is related to an instance
theory of automatization (Logan 1988)
› Conceptual advantage of the fossilization
account: no mind reading capacities are required
for the processing tasks
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Two kinds of fossilization
› Individual fossilization via learning/automatication
on an ontogenetic time scales (seconds-years)
› Cultural fossilization via iterated learning/cultural
evolution on a historical time scale (years-centuries)
Meanings are partly conventionalized within speech
communities and partly negotiated anew during
each individual interaction (Traugott & Dasher 2002)
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2 R-Expressions/Pronouns
Hendriks, Englert, Wubs & Hoeks (to appear):
Age differences in adults’ use of referring
expression
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Sentence Elicitation Study
A woman hold-ing
an ice cream cone
is walking past a
road sign.
Topic shift
The girl is eating
from the ice
cream cone.
The woman
comes across a
girl.
She gives the girl
an ice cream cone.
Target Picture
Well, theshe
woman
passes again an
ice cream van.
The woman buys
another ice cream
come.
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Results
› Elderly adults produce (non-recoverable) pronouns
significantly more often than young adults when referring to the old topic in the presence of a new topic.
› With respect to the comprehension task, no significant
differences were found between elderly and young
adults.
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Bidirectional Processing Account
› Speakers optimize bidirectionally and take
hearers into account when selecting a referring
expression.
› If the use of a pronoun will lead to an unintended
interpretation by the hearer, the speaker will use
an unambiguous definite noun phrase instead.
› Because elderly adults are more limited in their
processing capacities as speakers they will not
always be able to reason about the hearer’s
choices.
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Discussion
› Fits nicely with the earlier approach for pro/self
› Right prediction for elicitation studies: elderly
adults behave similar to children
› Wrong
prediction
for
pronoun/reflexive
interpretation studies: elderly adults should behave
similar to children
› Elderly (or stressed) people have no problems with
understanding pronouns; the problems are in
production only: it is complex to use an
unambiguous definite noun phrase instead of a
pronoun in certain situations
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The Fossilization Account
› The fossilization account is also able to describe the
difference between children and adults
› Learning leads to strengthening of PRO  TOPIC
› Unfortunately, it predicts that elderly adults behave
similarly to younger adults in case of Rexpressions/pronouns (there is no de-fossilization!)
› Wrong prediction! They should behave like children.
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Emergence of Bidirection or Fossilization?
› According to the bidirectional processing account the
crucial
developmental
stages
should
appear
synchronously for the different domains
› According to the fossilization solution (iterated
learning) the time course of the development is not
necessarily synchronized but may crucially depends on
factors of frequency and other factors of use
› Investigate different domains of structural similar
tasks!
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3 All/Some (Scalar
Implicatures)
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Some and all
10-11
›
›
Adults
Experimental Pragmatics: Noveck u.a.
• Some elephants live in the zoo (appropriate)
yes 90% 99%
• All elephants live in the zoo (inappropriate)
no 99% 99%
• Some elephants have trunks (inappropriate)
yes 85% 41%
• All elephants have trunks (appropriate)
yes 99% 96%
• Some elephants have wings (absurd)
no 99% 98%
• All elephants have wings (absurd)
no 99% 99%
Why do children sometimes think more logical than adults?
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Potential Answers
›
RT (finding relevant enrichments is somewhat
effortful – children’s processing resources are
rather limited; see Noveck & Sperber)
›
OT pragmatics has two potential answers
(1) Metalinguistic ability for perspective changing
(bidirectional reasoning) not yet developed
(2) Fossilization not yet progressed
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7 years
old
pro
pro
self
disj
self
conj
12 years
old
some
all
some
all
disj
conj
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Conclusions
› The existence of domain-dependencies is a strong
argument for the fossilization view
› Fossilization is a graded mechanism. In some cases it
can lead to full automatization (corresponding to
Levinson‘s GCI); in most cases it will not
› It is difficult to see how the bidirectional processing
account (and the RT processing account) can model
domain-dependencies without assuming an extra
automatization mechanism.
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4 General Conclusions
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Final Scores: Comprehension/Production
Bidir. Processing
(Hendriks et al.)
OT with
Fossilization
+/+
+/+
−/+
+/+
+/+
+/+
Children
Young adults
Elderly adults
+/+
+/+
+/+
+/+
+/+
+/−
Children
Young adults
Elderly adults
+/+
+/+
?
+/+
+/+
?
Pronouns & Refl
Children
Young adults
Elderly adults
R-Exp & Pron
All & Some
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Conclusions
› Production/comprehension asymmetries arise as a
result of a mismatch between the result of
unidirectional optimization and the result of
bidirectional optimization
› The asymetries can disappear
- when the language user is able to optimize bidirectionally
- when fossilization has taken place
› Both the bidirectional processing view and the
fossilization view are not really sufficient if taken per
se
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Towards a Solution
›
Combining the idea of Fossilization with
asymmetric OT
›
In asymmetric OT the speaker takes the listener
into account but not vice versa
›
We need independent motivation for that. At
the moment it’s a data fitting only!
With four parameters I can fit an elephant, and
with five I can make him wiggle his trunk