Dec 11, Human Parsing Do people use probabilities for parsing?! Sentence processing Study of Human Parsing

Dec 11, Sentence Processing Issues in Sentence Processing: Word ambiguity  The pitcher (ball player/container) threw the ball (sphere/dance) Syntactic ambiguity  The bus driver hit the fireman.  The bus driver was hit by the fireman. Ambiguous thematic roles  The teacher ate the spaghetti with the bus driver.  The teacher ate the spaghetti with the red sauce. Appropriate interpretation of a sentence usually requires semantic and contextual information.

Dec 11, Approaches Approaches to Sentence Processing Simple Parsing Heuristics Two-stage serial - “Garden Path” Initial parsing and Filtering (confirming or disconfirming the structurally-determined parse) Constraint-based or expectation-driven Probabilistic and context-sensitive aspects of sentence processing

Dec 11, Theories Ford et al (1982) Lexical sub-categorization preference The woman kept the dogs on the beach  The woman kept the dogs which were on the beach 5%  The woman kept them (the dogs) on the beach 95% “On the beach” refer to noun phrase or verb phrase Keep has categorization preference for VP with 3 constituents Discuss has categorization preference for VP with 2 constituents

Dec 11, Theories Bever (1970) Garden Path  Temporarily ambiguous sentences  One parse tree is more preferable than the other  The dispreferred parse is the correct one

Dec 11, Theories Bever (1970) Garden Path

Dec 11, Theories Trueswell (1993) Subcategorization preference: Forget prefers direct object rather than sentential complement

Dec 11, Theories Trueswell (1993) Garden Path Can be measured by increased time of reading  One word or phrase at a time  Eye tracking  Subjects spend more time on was for verb forget  Not for a verb than prefers sentential complement: hope

Dec 11, Theories Other types of preferences Jurafsky (1996) Part of speech  The complex houses married and single students and their families  Houses more likely to be noun than verb MacDonald (1993) Verb to be head or non head of a constituent Mitchell et al. (1995) Combination of lexical and phrase structure frequency

Dec 11, Theories Factors affecting Human Parsing Resource constraints (memory,…) Thematic structure (verb expecting semantic agent or patient) Semantic and contextual constraints

Dec 11, Theories Time Course of knowledge use?! Modularist Fraizer and Clifton (1996) Initial interpretation uses only syntactic knowledge Semantic, Thematic and Discourse knowledge come later

Dec 11, Theories Time Course of knowledge use?! Interactionist MacDonald (1994) Trueswell and Tanenhaus (1994) Tabor et al. (1997) Multiple knowledge sources interactively constrain the process of interpretation MacDonald (1994) These constraints are fundamentally probabilistic

Dec 11, Theories Jurafsky (1996) and Narayanan (1996) A probabilistic model: PCFG probabilities Syntactic and thematic subcategorization probabilities Could account for Garden-path examples!