Information Status.

Presentation on theme: "Information Status."— Presentation transcript:

1 Information Status

2 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.

3 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

4 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?

5 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….

6 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

7 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

8 Non-containing I bought a carton of eggs. One of them was broken.
A bus pulled up beside me. The driver was a monkey.

9 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

10 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

11 Hearer status of discourse entities in 1? 2?
(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? (2a) B: Why do you want to see the president? (2b) B: Have you talked to his secretary?

12 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

13 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. 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.

14 A rule-based approach: Stem the content words in the discourse
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

15 Boston Directions Corpus (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 & Sidner Given/new (Prince ’92), grammatical function, p.o.s.,…

16 Boston Directions Corpus: Describe how to get to MIT from Harvard
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

17 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

18 Hearer and Discourse Given/New Labeling
first enter <HG/DN the Harvard Square T stop> and buy <HI/DN a token> then proceed to get on <HI/DN the inbound um Red Line uh subway> and take <HG/DG the subway> from <HG/DG Harvard Square> to <HG/DN Central Square> and then to <HG/DN Kendall Square> then get off <HG/DG the T>

19 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?

20 Does Given/New Status Predict Deaccenting?
NPa HG HI HN DG DN Deaccented 37.1% 53.9% 26.2% 43.3% 38.8% Total 1009 406 130 596 950

21 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

22 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

23 Triangle Rectangle Cylinder Diamond Octagon

24 Context 1 Rectangle Triangle Cylinder Diamond Octagon

25 Context 2 Triangle Rectangle Cylinder Diamond Octagon

26 Context 3 Triangle Rectangle Cylinder Octagon Diamond

27 Target(A) Triangle Rectangle Cylinder Diamond Octagon

28 Target(B) Triangle Rectangle Cylinder Diamond Octagon

29 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

30 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

31 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)

32 Grammatical Role/Surface Position Accenting
CONTEXT TARGET GIVEN Subj D-obj Pp-obj 2.1 3.6 3.2 3.3 0.6 1.6 3.0 1.4 0.7 NEW 3.7 3.8 --

33 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

34 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

35 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

36 Will this help us predict deaccenting more accurately? Stay tuned…..
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….. NLP: FLC and BLC should be defined not only in terms of prior mention, but in terms of the thematic role entities play in prior mentions Linguistics: more straightforward

37 Next Class