Information Status

Varieties of Information Status –Contrast John wanted a poodle but Becky preferred a corgi. –Topic/comment The corgi they bought turned out to have fleas. –Theme/rheme The corgi they bought turned out to have fleas. –Focus/presupposition It was Becky who took him to the vet. –Given/new Some wildcats bite, but this wildcat turned out to be a sweetheart.

Today: Given/New Why do we care about Given/New? Defining Given/New: why is this hard? –Hearer-based and Discourse-based models Uses of Given/New information in NLP Identifying Given/New information automatically –Rule-based –Corpus-based –The Boston Directions Corpus –Laboratory studies suggest new directions

Why do we care about the given/new distinction? Building a model of the discourse –What do S and H believe to be true? –What is in their consciousness now? –What is ‘grounded’? Speech technologies –TTS: Given information is often deaccented while new information is usually accented –ASR?

Defining Given/New Halliday ‘67: –Given: Recoverable from some form of context –New: Not recoverable Chafe ’74 ’76: –Given: what S believes is in H’s consciousness –New: what S believes is not… –“Chafe-givenness” Yesterday I had my class disrupted by a bulldog/dog. I’m beginning to dislike dogs/bulldogs. But not vice versa….

Prince ’81: A Given/New Taxonomy Text as set of instructions from S to H on how to construct a discourse model –Model includes discourse entities, attributes, and links between entities –Discourse entities: individuals, classes, exemplars, substances, concepts (NPs) –Entities as ‘hooks’ on which to hang attributes (Webber ’78) Entities when first introduced are new

–Brand-new (H must create a new entity) I saw a dinosaur today. –Unused (H already knows of this entity) I saw your mother today. Evoked entities are old -- already in the discourse –Textually evoked The dinosaur was scaley and gray. –Situationally evoked The light was red when you went through it. Inferrables –Containing

I bought [a carton of eggs]. One of them was broken. [The door of the Bastille] was painted purple. –Non-containing A bus pulled up beside me. The driver was a monkey.

Given/New and Definiteness/Indefiniteness –Definiteness: subject NPs tend to be syntactically definite and old –Indefiniteness: object NPs tend to be indefinite and new I saw a black cat yesterday. The cat looked hungry. Definite articles, demonstratives, possessives, personal pronouns, proper nouns, quantifiers like all, every signal definiteness…but… There were the usual suspects at the bar. Indefinite articles, quantifiers like some, any, one signal indefiniteness…but…. This guy came into the room

What’s wrong with a simple Hearer-centric model of given/new? Hearer-centric information status: –Given: what S believes H has in his/her consciousness –New: what S believes H does not have in his/her consciousness But discourse entities may also be given and new wrt the current discourse –Discourse-old: already evoked in the discourse –Discourse-new: not evoked

(1) A: I’ve decided to make an appointment with Lee Bollinger. (2) B: Why do you want to see Bollinger? Hearer status of discourse entities in 1? 2? –If B is your roommate? your mother? a guy on the subway? Discourse status of discourse entities in 1? 2? What would be the hearer/discourse status of discourse entities in this version? (1) A: I’ve decided to make an appointment with Lee Bollinger. (2a) B: Why do you want to see the president? (2b) B: Have you talked to his secretary?

What does this new Hearer/Discourse given/new distinction provide? A way to separate what is explicit in the discourse model from what is believed to be in speaker/hearer cognitive model A way to explain given/new in more complex terms –To identify coreference relations –To explain deaccenting in ASR and TTS

Gross Oversimplification: Given Items Tend to be Deaccented Accenting and deaccenting: making items intonationally prominent or not Critical to get this distinction ‘right’ in TTS –Accenting everything makes it hard for people to understand anything, e.g.e.g. I like my cat and my cat adores me. One potato, two potato, three potato,… If a discourse entity is given for one speaker then it may or may not be given for another speaker.

How can we determine automatically whether a discourse entity is given or new? A rule-based approach: –Stem the content words in the discourse –Select a window within which incoming items with the same stem as a previous entity and within this window will be labeled ‘given’ Other items are ‘new’ Is this hearer-based? Discourse-based? How well does it work? –65-75% accurate (precision) depending on genre, domain

Boston Directions Corpus (Hirschberg & Nakatani ’96)Hirschberg & Nakatani ’96 Experimental Design 12 speakers: 4 used Spontaneous and read versions of 9 direction-giving tasks Corpus: 50m read; 67m spon Labeling –Prosodic: ToBI intonational labeling –Discourse: Grosz & SidnerDiscourse –Given/new (Prince ’92), grammatical function, p.o.s.,…

d1: dsp1: step 1: enter and get token first enter the Harvard Square T stop and buy a token d2: dsp2: inbound on red line then proceed to get on the inbound um Red Line uh subway Boston Directions Corpus: Describe how to get to MIT from Harvard

dp3 dsp3: take subway from hs, to cs to ks and take the subway from Harvard Square to Central Square and then to Kendall Square dp4: dsp4: get off T. then get off the T

Hearer and Discourse Given/New Labeling first enter and buy then proceed to get on <HI/DN the inbound um Red Line uh subway> and take from to and then to then get off

What could we do with this labeled data? Can we predict given/new? Can we predict what will be accented and what will be deaccented?

Does Given/New Status Predict Deaccenting? NPaHGHIHNDGDN Deaccented37.1%53.9%26.2%43.3%38.8% Total

What else might be at work? Given/new and grammatical function Hypothesis: how discourse entities are evoked in a discourse influences how ‘given’ they are E.g., How might grammatical function and surface position interact with the accentuation of ‘given’ items? Cases: –X has not been mentioned in the prior context –X has been mentioned, with the same grammatical function/surface position –X has been mentioned but with a different grammatical function/surface position

Experimental Design Major problem: –How to elicit ‘spontaneous’ productions while varying desired phenomena systematically? –Key: simple variations and actions can capitalize upon natural tendency to associate grammatical functions with particular thematic roles for a given set of verbs

Triangle Cylinder Diamond Rectangle Octagon

Triangle Cylinder Diamond Rectangle Octagon Context 1

Triangle Cylinder Diamond Rectangle Octagon Context 2

Triangle Cylinder Diamond Rectangle Octagon Context 3

Triangle Cylinder Diamond Rectangle Octagon Target(A)

Triangle Cylinder Diamond Rectangle Octagon Target(B)

Materials 9 objects in visual display 3 event types: –X covers Y (subject, object) –X pushes Y against Z (subject, object, pp-object) –X touches Y (subject, object) 75 scenarios of 4 sequences of actions each –3 “context” turns (all containing the same given item) –1 “target” turn (always containing the same given item) –3x3 design (given item is subj, direct object or pp-obj in context and same or not in target) with 5 scenarios per cell –2 controls: all new, all given objects (15 scenarios each) –Presented in random order

Experimental Conditions 10 native speakers of standard American English Subject and experimenter in soundproof booth Subject told to describe scenes to confederate outside the booth, visible but with providing no feedback 10 practice scenarios ~20 minutes per subject

Prosodic Analysis Target turns excised and analyzed by two judges independently for location of pitch accents for each referring expression: accented (2), unsure (1), deaccented (0)  accentedness score from 0-4 (81% agreement for 0 and 2 scores)

Grammatical Role/Surface Position Accenting CONTEXTTARGET GIVENSubjD-objPp-obj Subj D-obj Pp-obj NEW

Findings In general –Items that differ from context to target in grammatical function or surface position tend to be accented –Items that share grammatical function and surface position tend to be deaccented But –Subjects tend to be accented more often than objects, even if previously mentioned in the same role –Direct objects and pp-objects tend to be more distinguished from subjects than from one another

How can we explain these observations? Consider our examples, e.g. subj  D.O. The TRIANGLE touches the CYLINDER. The triangle touches the DIAMOND. The triangle touches the OCTAGON. The RECTANGLE touches the TRIANGLE. An entity may be ‘given’ or ‘new’ wrt the role it plays in the discourse

Given/New Sensitive to the Role the Discourse Entity Plays E.g., a discourse entity may retain a given or take on a new thematic role –By the time the target is uttered, ‘triangle’ is established both as a ‘given’ discourse entity and as the discourse topic (or BLC in centering theory) –But this status has been established for ‘triangle’ as agent –What is new, and, perhaps, focused in the target is ‘triangle’s’ new thematic role as patient – the players are the same but the roles are different

Consequences for NLP –Identification of given/new status must be sensitive to more complex model of context (grammatical function/thematic role) –Will this help us predict deaccenting more accurately? –Stay tuned…..

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