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Implicature, Presupposition, and Speech Acts

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Implicature, Presupposition, and Speech Acts A Goal for Question-Answering Systems Understanding queries S: Are you traveling to La Guardia? U: I m going to New York. – PowerPoint PPT presentation

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Title: Implicature, Presupposition, and Speech Acts


1
  • Implicature, Presupposition, and Speech Acts

2
A Goal for Question-Answering Systems
  • Understanding queries
  • S Are you traveling to La Guardia?
  • U Im going to New York.
  • U When does the 5 oclock train leave from
    Newark?
  • S (thinks) U believes there is a 5 oclock train
    from Newark.
  • S I heard you say New York City?
  • U New York City./?

3
  • Cooperative responses
  • Correcting misconceptions
  • U When does the 5 oclock train leave from
    Newark?
  • S (thinks) U believes there is a 5 oclock train
    from Newark.
  • S There is no 5 oclock train from Newark there
    is a 520 tho.
  • Providing more information than is asked for
  • U Do I have the 500 minimum in that account?
  • S1 Yes.
  • S2 You have 739.

4
Discourse Pragmatics
  • Context-dependent meaning, invited inference,
    intended meaning vs. propositional content
  • Speech Acts and illocutionary force
  • Presupposition
  • Implicature
  • Conversational
  • Conventional

5
Speech Acts (Austin, Searle)
  • Can you tell me the time? Can you open the
    window?
  • Locutionary acts the act of uttering
  • Illocutionary acts the act the utterance is
    intended to perform (question, assertion,
    exclamation)
  • Perlocutionary acts the rhetorical act intended
    by S in performing the illocutionary act (getting
    H to do something, conveying to H that S is
    cold,)

6
Linguistic Cues to Speech Act Identification
  • Performative verbs
  • Can indicate illocutionary force promise, order,
    ask, beseech, deny, apologize, curse
  • But not perlocutionary force (I convince you to
    vote for me for president)
  • Speech acts in NLP often identified with
    illocutionary force
  • Cottage industry in identifying speech acts
    automatically from large labeled corpora using
    lexical and acoustic/prosodic cues

7
Why Does It Matter?
  • S/DA recognition important for
  • Turn recognition (which grammar to use when)
  • Turn disambiguation, e.g.
  • S What city do you want to go to?
  • U1 Boston. (reply)
  • U2 Boston? (request for information)
  • S Do you want to go to Boston?
  • U1 Boston. (confirmation)
  • U2 Boston? (question)

8
  • Same word/phrase -- different speech acts
  • Okay acknowledgment, acceptance, question,
  • Different word/phrase -- same speech act
  • Yes, Right, Okay, Certainly,..
  • Okay
  • Contours distinguish different uses (Hockey 91)
  • Contours context distinguish different uses
    (Kowtko 96)

9
Using Prosodic Information for DA Identification
  • Nöth et al 99 prosodic information improves DA
    identification
  • Prosodic phrase boundaries signal potential DA
    boundaries
  • Iding most frequently accented words in training
    corpus improves key-word selection for
    identifying DAs
  • ACCEPT (ok, all right, marvelous, Friday, free)
  • SUGGEST (Monday, Friday, Thursday, Wednesday,
    Saturday)

10
Presupposition
  • That which is taken for granted, given some
    linguistic expression X
  • The King of France is bald.
  • All of Hermans children are bright. (How many
    children does Herman have?)
  • Test the negation and question presuppose the
    same thing
  • The King of France is not bald. Is the King of
    France bald?
  • None of Hermans children are bright. Are any of
    Hermans children bright?

11
Linguistic Cues to Presupposition
  • Factives
  • Its a shame that X vs It is thought that X
  • I realized that X vs I thought that X
  • He managed to X vs He tried to X
  • She regretted that X vs She feared that X
  • ...
  • Definites
  • The X are Y (The King of France is bald vs. The
    King of France is dead)
  • Lexical presupposition

12
  • John assasinated Bill (Bill died, the killing was
    intentional, the victim had some political
    status)
  • Susan is accused of X (X is bad)
  • Susan was criticized for X (X is bad and Susan
    did X)
  • Merlin is a bachelor (Merlin is an unmarried male
    person)
  • Presuppositions can be suspended but they cannot
    be felicitously denied
  • All of Hermans children are bright, though he
    has no children.
  • All of Hermans children are bright, if he indeed
    has children.

13
Why do we care?
  • Presuppositional information adds facts/beliefs
    to the database for NLP systems
  • Information to store and check for accuracy
  • My wife will also be a driver (S has a spouse)
  • My number is 212-555-1212 (S has a telephone
    account)
  • Ill take the red-eye (S believes there is a
    red-eye)
  • Im upset about being charged for a call to
    Ethiopia (S was charged for a call to Ethiopia)
  • Im a bachelor. (S is an unmarried male person)

14
Conversational Implicature
  • H. Paul Grice conversation is different from
    formal logic
  • and is not , or is not v, some is not
  • George got married and had a baby. Was it a boy
    or a girl? Some people sent baby gifts. Do
    they need clothes or toys? All the grandparents
    came to visit.
  • Cooperative Conversation
  • Make your conversational contribution such as is
    required, at the stage at which it occurs, by the
    accepted purpose or direction of the talk
    exchange in which you are engaged

15
Maxims of Cooperative Conversation
  • Maxim of Quantity
  • 1. Make your contribution as informative as is
    required (for the current purposes of the
    exchange)
  • 2. Do not make your contribution more than is
    required.
  • Maxim of Quality
  • Try to make your contribution one that is true.
  • 1. Do not say what you believe to be false.
  • 2. Do not say that for which you lack adequate
    evidence.
  • Maxim of Relation Be relevant

16
  • Maxim of Manner Be perspicuous
  • 1. Avoid obscurity of expression.
  • 2. Avoid ambiguity.
  • 3. Be brief (avoid unnecessary prolixity).
  • 4. Be orderly.
  • Maxims may be
  • Observed
  • John got into Columbia and won a scholarship.
  • Violated quietly
  • I never said that.
  • Flouted
  • He has excellent handwriting.

17
  • Speakers may not be able to observe all maxims
    simultaneously
  • Implicature interpretation requires both S and H
    to be in sync
  • That which S licenses and H infers via the CP and
    the Maxims
  • A. I got an A on that exam.
  • B. And Im Queen Marie of Rumania.
  • A. Where did you go?
  • B. Out.

18
  • A Where does Arnold live?
  • B Somewhere in southern California.

19
Other Implicatures
  • Generalized Conversational, e.g. indefinites
  • A car ran over Johns foot. (not Johns car)
  • John broke a foot yesterday. (Johns foot)
  • John broke a nose yesterday. (not his own)
  • Conventional
  • George is short but brave.
  • George is short therefore he is brave.

20
Distinguishing among Types of Meaning
  • The King of France is bald but handsome.
  • Propositional content
  • What is asserted (entailed)
  • Presupposition
  • What is taken for granted, even if the
    propositional content is negated or questioned

21
  • What are you getting me for Christmas?
  • The King of France is bald but handsome.
  • Conversational implicature
  • What is implicated
  • Cancelable/defeasible
  • Nondetachable
  • Conventional Implicature
  • What is implicated
  • Not cancelable/defeasible
  • Not nondetachable

22
For Next Class
  • Read Ch 4.7
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