0217_sentence_2

0217_sentence_2 - Psycholinguistics: Sentence Processing II...

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Psycholinguistics: Sentence Processing II 9.59; 24.905 February 17, 2005 Ted Gibson
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Today’s lecture 1. Parsing 1. Top-down 2. Bottom-up 3. Left-corner 4. (Chart parsing: see reading.) 2. Human sentence comprehension: How to address the question of how sentences are comprehended. 3. Information sources used in sentence comprehension.
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1. What is parsing? 2. Parsing strategies 1. Top-down 2. Bottom-up 3. Left-corner 4. (Chart parsing) Gibson lab, MIT
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What is parsing? (1) The dog bites the man. (2) The man bites the dog. (3) *The dog bites man the. (1) = boring, (2) = interesting, (3) = not English Gibson lab, MIT
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What is parsing? (1), (2), and (3) have the same words BUT: structure different different meaning for (1) and (2) Not every sentence structure is possible: (3) A grammar tells you what are possible sentence structures in a language: S NP VP NP Det N etc. Gibson lab, MIT
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Why is parsing hard? Infinite number of possible sentences We can understand and say sentences we never heard before. Therefore representations of sentences’ meanings cannot be stored in and retrieved from memory. Ambiguity The man saw the woman on the hill with the telescope . Word-level ambiguity: saw Phrase-level ambiguity: PP-attachments Gibson lab, MIT
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What is parsing? Parsing: discover how the words in a sentence can combine, using the rules in a grammar. Gibson lab, MIT
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What is parsing? Parser sentence representation of meaning Generator representation of meaning sentence Gibson lab, MIT
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Parsing strategies - intro Our sentence: The man likes the woman Our grammar: S NP VP NP VP Det Noun Verb NP Det Noun Noun Verb Verb the man woman likes meets Gibson lab, MIT
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Parsing strategies - intro Our grammar is unambiguous: not the case in real life VP Verb I walk VP Verb NP I eat the apple VP VP PP I see you with the telescope Gibson lab, MIT
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Parsing strategies - intro How to deal with ambiguity in grammar: Serial approach: try one rule at a time, then backtrack if necessary need to specify which rule to start with Parallel approach: work on all alternative rules need data structure that can contain set of parse trees Gibson lab, MIT
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Parsing strategies - intro Top-down parsing: Start by looking at the rules in grammar See if the input is compatible with the rules Bottom-up parsing: Start by looking at input See which rules in grammar apply to input Combination of top-down and bottom-up: Only look at rules that are compatible with input Gibson lab, MIT
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Top-down - intro Assume that the input will eventually form a sentence Invoke S-node and all its possible extensions Keep expanding nodes until you find matching input Stack: keep track of what you still need to find in order to get grammatical sentence Gibson lab, MIT
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Top-down - intro Ambiguity terminology (not relevant to our
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This note was uploaded on 11/11/2011 for the course BIO 9.07 taught by Professor Ruthrosenholtz during the Spring '04 term at MIT.

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0217_sentence_2 - Psycholinguistics: Sentence Processing II...

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