Implicature Presupposition and Speech Acts CS 4705 A

Implicature, Presupposition, and Speech Acts CS 4705

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

• Cooperative responses – Correcting misconceptions U: When does the 5 o’clock train leave from Newark? S (thinks): U believes there is a 5 o’clock train from Newark. S: There is no 5 o’clock train from Newark; there is a 5: 20 tho. – Providing more information than is asked for U: Do I have the $500 minimum in that account? S 1: Yes. S 2: You have $739.

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

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, …)

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

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? U 1: Boston. (reply) U 2: Boston? (request for information) S: Do you want to go to Boston? U 1: Boston. (confirmation) U 2: Boston? (question)

– 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)

Using Prosodic Information for DA Identification Nöth et al ’ 99: prosodic information improves DA identification – Prosodic phrase boundaries signal potential DA boundaries – Id’ing 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)

Presupposition • That which is taken for granted, given some linguistic expression X The King of France is bald. All of Herman’s 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 Herman’s children are bright. Are any of Herman’s children bright?

Linguistic Cues to Presupposition • Factives: It’s 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

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 Herman’s children are bright, though he has no children. All of Herman’s children are bright, if he indeed has children.

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) I’ll take the red-eye (S believes there is a red-eye) I’m upset about being charged for a call to Ethiopia (S was charged for a call to Ethiopia) I’m a bachelor. (S is an unmarried male person)

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

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

• 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….

• 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 I’m Queen Marie of Rumania. A. Where did you go? B. Out.

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

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

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

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

For Next Class • Read Ch 4. 7