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Where to next? Pronoun interpretation as a side effect of discourse direction

Where to next? Pronoun interpretation as a side effect of discourse direction. Hannah Rohde, Andy Kehler, & Jeff Elman UC San Diego. CUNY Conference on Human Sentence Processing, March 29-31 2007. Bill. He. John. He. Transfer Verb. Goal (to-phrase). Ambiguous Pronoun Prompt.

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Where to next? Pronoun interpretation as a side effect of discourse direction

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  1. Where to next? Pronoun interpretation as a side effect of discourse direction Hannah Rohde, Andy Kehler, & Jeff Elman UC San Diego CUNY Conference on Human Sentence Processing, March 29-31 2007

  2. Bill He John He Transfer Verb Goal (to-phrase) Ambiguous Pronoun Prompt Source (subject) Transfer of possession (Stevenson et al. 1994) handed a book to . ______________. John Bill He recommended it thanked John • 50/50: Goal continuations / Source continuations • No subject preference or grammatical parallelism • Two explanations considered: • Thematic Role Preference • Event Structure Bias

  3. Outline • Background: Rohde et al. 2006 • Test Thematic-Role and Event-Structure biases • Alternative account: Discourse Coherence • Experiments 1 & 2: test predictions of a coherence- based model using story continuations • Preliminary results: discourse effects in relative clause attachment

  4. handed a book to . ______ . JohnSOURCE BillGOAL He was handing a book to . ___ . JohnSOURCE BillGOAL He Explaining salience of Goal (Rohde et al. 2006) • Thematic role preference or event structure bias? Equivalent thematic roles but different event structure Effect of aspect F(1,48)=50.622 p<0.0001 • Goal bias ~ side effect of Event Structure

  5. Matt He Matt passed a sandwich to David. He said thanks. Matt passed a sandwich to David. He didn’t wantDavid to starve. [Explanation: Q  P] David He [Result: P  Q] Effects of coherence (Rohdeet al. 2006) • Establishing coherence: infer a relationship between the meanings expressed by two sentences (P&Q below) (Hobbs 1979, Kehler 2002) • Causal relations (Explanation, Result, Violated Expectation)

  6. Matt passed a sandwich to David. He ate it up. Matt He Matt passed a sandwich to David.Hedidsocarefully. [Elaboration: infer P from both S1 and S2] He David [Occasion: infer initial state of event described in S2 to be final state of event described in S1] Coherence cont. • Similarity relations (Parallel, Elaboration) • Contiguity relations (Occasion)

  7. Discourse coherence effects(Rohde et al.) • Goal bias following perfective context sentences limited to Occasion & Result (see Arnold 2001) • Interpretation as side effect of coherence distribution

  8. Shift coherence  shift interpretation • Test predictions of a coherence-driven model • More Occasion/Result  more Goal resolutions • More Explanation/Elaboration/Violated-Exp  more Source

  9. Experiment 1: objects-of-transfer • Proposal: elicit different continuations with different objects • Stimuli: normal and bizarre objects John handed a book to Bill. He ___________ . John handed a bloody meat cleaver to Bill. He __ . • Predictions: • If… Abnormal objects  more Explanations and Explanations  Source bias • More Source continuations for (9) than (8)

  10. Methodology • Subjects: 69 monolingual English speakers • Task: write 50 continuations, just like Rohde et al. • Stimuli: 21 transfer-of-possession like Rohde et al. (+ bizarre objects) • Evaluation: judges assess coherence/interpretation • Analysis: • Effect of within-subject factor of Object Type on • Coherence (Elab/Expl/Occ/Par/Res/Viol-Exp) • Pronoun interpretation (Source/Goal) • Mixed-effects logistic regression • Controls for random effects of Subject and Item

  11. Consistent prob(Source|coh) Coherence Rohde et al. Exp 1 Source Source Explanation 0.75 0.82 Elaboration 0.99 0.99 Violated-expectation 0.87 0.81 Occasion 0.20 0.17 } } Result 0.16 0.05 Goal Goal Parallel 0.45 0.71 Results Coherence varies by object p<0.0001

  12. Results • No effect of object type on pronoun interpretation Subjects: F(1,68)= 0.052 p<0.820 Items: F(1,20)=0.111 p<0.743

  13. John handed a book to Bill. He ___________ . Experiment 2: ‘What next?’ or ‘Why?’ • Stimuli & Design: identical to Rohde et al. 2006 • Instructions: write continuations answering either “What happened next?” or “Why?” • Predictions: • “What next?”  more Occasions  Goal bias • “Why?”  more Explanations  Source bias

  14. Methodology • Subjects: 42 monolingual English speakers • Task: identical to Rohde et al. 2006 (w/instructions) • Stimuli: identical to Rohde et al. 2006 • Evaluation: judges assess coherence/interpretation • Analysis: • Effect of between-subject factor of Instruction Typeon coherence distribution & pronoun interpretation

  15. Consistent prob(Source|coh) Coherence Rohde et al. Exp 2 Explanation 0.75 0.81 Elaboration 0.99 1.00 Violated-expectation 0.87 0.81 Occasion 0.20 0.28 Result 0.16 0.11 Goal Parallel 0.45 0.46 Source Results Coherence varies w/instruction (p<0.0001)

  16. Results • Effect of Instruction type on pronoun interpretation F(1,20)=52.672 p<0.0001

  17. Predicting pronoun interpretation • Predict % Source Resolutions in Exp 2 using: • Exp2 coherence breakdown • Exp1 conditional probabilities Coherence p(Source) Explanation 0.82 Elaboration 0.99 V-E 0.81 Occasion 0.17 Result 0.05 Parallel 0.45

  18. Capturing subject variation “What next” “Why” linear regression R2=0.604 F(1,40)=61.097, p<0.0001

  19. Consistency of biases across conditions R2 value/ANOVA Conditional Probability Estimator Exp1: perf, normal objects R2=0.606, F(1,40)=61.612* Exp1: imp, normal objects R2=0.627, F(1,40)=67.371* Exp1: perf, abnormal objects R2=0.561, F(1,40)=51.165* Exp1: imp, abnormal objects R2=0.586, F(1,40)=51.165* Exp1: average across verbal aspects & object types R2=0.604, F(1,40)=61.097* * Indicates p<0.0001

  20. Summary • Shift coherence  Shift pronoun interpretation No model relying only on surface-level cues can account for observed variation, since stimuli were near-identical (Exp 1) or identical (Exp 2) • Need richer models incorporating discourse-level factors (see Wolf et al. 2004; Kertz et al. 2006)

  21. high low the musician plays the children are at the club downtown. musical prodigies themselves. • Function of a relative clause John despises the employee who is always late. Implicit Causality (NP2 IC) verbs attribute cause to direct object What else can discourse do for you? • Relative clause attachment ambiguity Beth babysits the children of the musician who ____ • Proposal: try to shift RC attachment using verbs that require Explanations and that attribute cause to the referent occupying higher NP

  22. the musician plays  low at the club downtown. the children scream and yell during rehearsals.  high F(1,51)=31.082 p<0.0001 p<0.0001 Predictions & results nonIC: Beth babysits the children of the musician who _____ IC: Beth despises the children of the musician who ______ Further evidence that discourse influences interpretation

  23. References Arnold, J. E. (2001) The effects of thematic roles on pronoun use and frequency of reference. Discourse Processes, 31(2): 137-162. Chambers, G. C. & Smyth, R. (1998) Structural parallelism and discourse coherence: A test of Centering Theory. Journal of Memory and Language, 39: 593-608. Crawley, R., Stevenson, R., & Kleinman, D. (1990) The use of heuristic strategies in the interpretation of pronouns. Journal of Psycholinguistic Research, 4: 245–264. Kameyama, M. (1996) Indefeasible semantics and defeasible pragmatics. In M. Kanazawa, C. Pinon, and H. de Swart, editors, Quantifiers, Deduction, and Context. CSLI Stanford, pp. 111-138. Hobbs, J. R. (1979) Coherence and coreference, Cognitive Science, 3:67-90. Hobbs, J. R. (1990) Literature and Cognition. CSLI Lecture Notes 21. Stanford, CA. Kehler, A. (2002) Coherence, reference, and the theory of grammar. CSLI Publications, Stanford, CA. Kertz, L., Kehler, A., & Elman, J. (2006) Grammatical and Coherence-Based Factors in Pronoun Interpretation. 28th Annual Conference of the Cognitive Science Society, Vancouver, July 2006. Moens, M. & Steedman, M. (1988) Temporal ontology and temporal reference. Computational Linguistics 14(2):15-28. Smyth, R. H. (1994) Grammatical determinants of ambiguous pronoun resolution. Journal of Psycholinguistic Research, 23: 197-229. Stevenson, R., Crawley R., & Kleinman D. (1994) Thematic roles, focusing and the representation of events. Language and Cognitive Processes, 9:519–548. Wolf, F., Gibson, E. & Desmet, T. (2004) Coherence and pronoun resolution. Language and Cognitive Processes, 19(6): 665-675

  24. Interpretation (instr x aspect interaction p<0.0001) Coherence (instr x aspect interaction p<0.0001) …“What happened next?” John gave a book to Bill. He ___________ . John was giving a book to Bill. He ___________ . Variation by instruction and aspect

  25. Discourse coherence effects

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