1 Special Electives of Comp.Linguistics: Processing Anaphoric Expressions Eleni Miltsakaki AUTH Fall 2005-Lecture 5

2 Brief review Referential and non-referential pronouns –What are they? Centering –Where is it coming from? –What is it? –What are the basics of the Centering Model? Anaphora resolution algorithms –What is the BFP algorithm? –What is ‘functional centering’? –What is the S-list algorithm?

3 Plan for today Semantic focusing and the relational hypothesis “Interpreting pronouns and connectives: Interactions among focusing, thematic roles and coherence relations” (2000) (R. Stevenson, A. Knott, J. Oberlander and S. McDonald) Still to come –Couple more psycholinguistic studies on anaphora resolution –Linguistic theories of anaphora resolution –Automated systems for anaphora resolution –PROJECTS!

4 The focusing hypothesis Verbs and connectives have focusing properties –The focusing properties of the verb direct attention to the endpoint or consequence of the described event –The focusing properties of the connective depends on its meaning

5 Example with ‘so’ John criticized Bill so he tried to correct the fault. The verb puts Bill, the patient, in focus The connective ‘so’ focuses on consequences and reinforces the focus on Bill

6 Example with ‘because’ John criticized Bill because he failed to correct his faults. Verb brings ‘Bill’ in focus The connective directs attention to the cause, shifts attention from ‘consequence’ to ‘cause’, so less likely to refer to ‘Bill’  The focus of the utterance changes as new input is processed

7 Stevenson et al (1994) 3 types of verbs –Transfer (e.g., pass) –Action (e.g., hit) –State (e.g., impress) Thematic roles –Transfer: Goal-Source –Action: Agent-Patient –State: Experiencer-Stimulus 2 thematic role orders –Goal-Source, Source-Goal –Agent-Patient, Patient-Agent –Experiencer-Stimulus, Stimulus-Experiencer 4 types of connectives –And –So –Full stop –because

8 Sample material for Stevenson et al (1994) John hit Bill/Bill was hit by John so/because/and/. John gave the book to Bill/Bill took the book from John so/because/and/. John liked Bill/Bill pleased John so/because/and/.

9 Results from Stevenson et al 1994

10 Analysis of results Goal and patient always preferred in transfer and action sentences The preferred thematic role in state sentences depends on the connective: Experiencer for ‘so’ and ‘and’, Stimulus for ‘because’ and ‘.’

11 The relational hypothesis The referent of a pronoun is determined by the choice of coherence relation and not what is in focus. RESULT: the thematic role associated with the endpoint of the eventuality, patient PURPOSE: the agent of an event (so this relation is incompatible with states) NARRATIVE: the agent of an event

12 Ambiguity ‘So’ is ambiguous –CONSEQUENCE Bill handed the plate to Bob so he balanced his glass on it. –PURPOSE Bill handed the plate to Bob so he could refill his glass.

13 Experiment 1 3 types of verb –Transfer (e.g., pass) –Action (e.g., hit) –State (e.g., impress) Thematic roles –Transfer: Goal-Source –Action: Agent-Patient –State: Experience-Stimulus 2 connectives –So (RESULT-PURPOSE) –because

14 Sample material from exp. 1 Transfer –Goal-Source: John seized the comic from Bill so/because he… –Source-Goal: John passed the comic to Bill so he… Action –Patient-Agent: Patrick was hit by Joseph so/because he… –Agent-Patient: Joseph hit Patrick so/because he… State –Experiencer-Stimulus: Ken admired Geoff because/so he… –Stimulus-Experience: Ken impressed Geoff so/because he…

15 Results from Exp. 1

16 Analysis of results of Exp. 1 In transfer and action verbs, the preferences fro Goal and Patient were reinforced with ‘so’ and reduced with ‘because’ In state verbs, there was a preference for Experiencer with ‘so’ and for the Stimulus with ‘because’ About relations: –Transfer verbs (pronoun refers to Goal): PURPOSE continuations significantly greater than chance in both thematic orders. RESULT continuations did not differ from chance –Action verbs (pronoun refers to Patient): RESULT continuations were significantly greater than chance in both thematic orders. PUPROSE continuations were significantly less frequent in Patient-Agent, chance for Agent-Patient –State verbs (pronoun refers to Experiencer). RESULT continuations were significantly greater than chance in both thematic orders. PURPOSE continuations significantly lower in Stimulus-Experiencer. No PURPOSE continuations in Experiencer-Stimulus

17 Conclusions from Exp. 1 Focusing hypothesis –Action and transfer: pronoun resolves to Patient-Goal respectively. The focus is maintained when the connective is ‘so’ –State: Connective must be encountered before attention can be directed: Experiencer in state verbs when the connective is ‘so’  Results consistent with the focusing hypothesis Relational hypothesis –Do the preferred pronominal interpretations co-occur with RESULT coherence relations? –YES for actions and states –NO for transfers (PURPOSE predominated in this case) BUT! –A unique coherence relation is consistent with the interpretation of the pronoun within each verb type but not across verbs. PURPOSE in transfer  Goal referents, RESULT in action  Patient referents, RESULT in states  Experiencer referents  Strong view of the relational hypothesis is not supported  Weak view of the relational hypothesis is supported

18 Summary for Exp. 1 Thematic role focusing and coherence relations go together –Action/State: pronoun refers to the focused thematic role associated with the consequence of the event and the relation is RESULT. –Transfer: pronoun refers to the focused thematic role associated with the endpoint of the event and the relation is PURPOSE. –Cf ranking is based on functional information status Participants’ continuations reveal that they selected the meaning of ‘so’ in a way that maximized consistency between the meaning of the verb, the focused entity, the coherence relation and the interpretation of the pronoun.  “Language users strive to keep verb meaning, focusing, coherence relation and pronominal interpretation in alignment.”