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Sentence Comprehension. Where are we? Levels of processing in language processing –Speech/letter perception –Word recognition Lexical access vs. lexical.

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Presentation on theme: "Sentence Comprehension. Where are we? Levels of processing in language processing –Speech/letter perception –Word recognition Lexical access vs. lexical."— Presentation transcript:

1 Sentence Comprehension

2 Where are we? Levels of processing in language processing –Speech/letter perception –Word recognition Lexical access vs. lexical selection –Sentence comprehension Syntactic (is this a module?) Semantic analysis –Discourse/Message level Pragmatics

3 Word Recognition and Sentence Comprehension  Word recognition is an essential input to sentence comprehension.  What does this mean?  In both reading and listening, we begin to develop syntactic & semantic representations of the sentence as soon as we hear the first words (recall Marslen-Wilson, 1973). The professor explained… The horse raced…

4 Garden Path Sentences The horse raced past the barn. [ NP ] [ VP ] The horse raced past the barn fell. [ NP [ relative clause ] ] [ VP ]  We build sentence-level structures and interpretations incrementally.  There is a lot of temporary ambiguity.  Sometimes we choose the wrong alternative.

5 Incremental Parsing & Interpretation Garden path sentences (Bever, 1970) –The horse raced past the barn fell. (Main Clause/Relative Clause ambiguity) GP depends upon whether first NP is a good agent/experiencer, and on frequency of past participle form of verb (Trueswell, 1996). –The thief (who was) searched by the police had weapons. [good agent, infreq participle] –The award (that was) accepted by the man was impressive. [poor agent, freq participle] Support for Constraint-based Lexicalist Account of syntactic processing (parsing)

6 Two critical components of Sentence Comprehension Syntactic Analysis Semantic Interpretation Within a language, syntactic structure largely determines meaning (or vice versa) Put the ball in the box on the table.  Can semantic interpretation guide syntactic analysis in a top-down manner?  Constraint-based lexicalist – YES  Frazier’s Garden Path model -- NO

7 Sentence Comprehension difficulty is not always related to ambiguity/garden path! The paper that the pencil that the chalk touched marked burned. Even without ambiguity, it is difficult to identify the hierarchical structure. Once you figure out the structure, the meaning becomes clear... The paper burned. that the pencil marked __ that the chalk touched __

8 Do semantic cues help? The water that the boy that the bee stung carried spilled. The water spilled. that the boy carried __ that the bee stung __

9 Frequently, processing difficulty is caused by a structural ambiguity. The cotton shirts are made from grows in Georgia. –(The cotton shirts) (are made from...) –(The cotton (shirts are made from)) (grows in...) Two syntactic structures are possible. If you select the wrong one, you “garden path.” But ambiguity doesn’t necessarily cause processing difficulty; we’re usually unaware of structural ambiguities.

10 Theories of sentence comprehension should be able to predict processing difficulty in both ambiguous and unambiguous sentences. Structurally ambiguous sentences have been especially important in testing theories, because an important distinction among theories is the role of top-down contextual information in syntactic ambiguity resolution.

11 Frazier’s Garden Path Theory 1.As you recognize each word, syntactic category is input to “parsing module”. 2.Syn cat inputs trigger operation of PS rules. When input is consistent with multiple PS rules… a)Add new constituent using minimal number of nodes. “MAS” b)Given 2 equally minimal options, attach to current constituent. “LC” 3.Pass structure to semantic interpreter. Is this the Minimal Attachment?

12 Predictions Processing difficulty at point of disambiguation whenever minimal attachment (or late closure) turns out to be wrong.  Potential Problem: A lot hinges on how you draw the trees (i.e., exactly what are the PS rules?)

13 A well-specified (but very specific) Constraint- based model The horse raced by… This model predicts local difficulty at the verb in a reduced relative/main clause ambiguity.

14 Using multiple constraints to resolve syntactic ambiguities Frazier’s approach ignores relevant information in the interests of reducing processing load Constraint-based approaches assume that we have the capacity to use constraints from any level of representation immediately –The horse raced past the barn fell. –The guests invited to the party arrived.  Is initial NP a better subject or direct object of first verb?  Is there a unique referent for the NP in the discourse, or do you need a modifier to tell you which horse/guest?  Is the past tense or the participle more frequent, for this verb?

15 How do we get from the words to a sentence-level representation? Word could trigger rules in a phrase structure grammar, which generate hierarchical structure (as in Frazier’s Minimal Attachment approach) : The = Det; Det + N = NP Horse = N Raced = V; V = VP, V + NP = VP The lexicon might actually encode structure, so that pieces of PS trees are accessed during word recognition and simply pieced together at matching nodes. (See Figure 3 of F&B,2004)

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17 Most words are associated with multiple “trees” I like math. friends like mine eat like a pig

18 John ate an apple like... Which one do you use? Syntactic ambiguity resolution as lexical ambiguity resolution.

19 John ate an apple like...

20 Sentence understanding so far… Syntactic and semantic representations built up incrementally –Garden path sentences –Difficult, but unambiguous structures Frazier’s parser is automatic & dumb –Ignoring context/semantics, build simplest structure allowed by PS rules Constraint-based lexicalist parser is interactive and smart –Use any relevant knowledge to choose best structure at point of ambiguity

21 Do Chinese readers use verb transitivity bias to immediately interpret EC? Judge help ___ rob… … and steal. (Judge help PRO rob and steal) …de poor people. (Judge help [__ i rob RC] people i ) At “rob”, you must posit an EC, but “help” allows for either PRO (implausible) or trace. Transitivity bias of “help” is cue for analyzing EC –Intransitive/Subject Control reading = PRO –Transitive reading = Trace Hsieh & Boland, in progress

22 Manipulate transitivity of 1 st Verb PRO Ambig (Intransitive-biased) 那個法官幫忙搶劫和偷竊 The judge help ? rob and steal “The judge helps to rob and steal.” PRO Unambig (Oblig Intransitive) 那個法官打算搶劫和偷竊 The judge intend PRO rob and steal “The judge intends to rob and steal.” Trace Ambig (Transitive-biased) 那個法官記得搶劫的窮人 The judge remember ? rob RC poor people “The judge remembers the poor people who robbed.” Trace Unambig (Oblig Transitive) 那個法官同情搶劫的窮人 The judge sympathize-with __ rob RC poor people “The judge sympathizes with the poor people who robbed.” Anomaly No Anomaly PRO: transitivity bias; immediate interp Trace: plausibility PRO: immediate interp Trace: transitivity bias; plausibility

23 Results Transitivity Bias guides analysis of EC

24 Implications As in English (e.g., subject/object ambiguity), verb transitivity bias is used to guide parsing. –Verb transitivity cue outweighed plausibility cue Because it was more rapidly available? Possible that both alternatives were considered in ambiguous conditions

25 Syntactic Parallelism Debate Lexical & semantic knowledge guide selection of best analysis at syntactic ambiguity. –Trueswell (1996) The award accepted… vs. The thief searched… Processing costs (garden path) observed if structure is later disambiguated in another manner. Support for the hypothesis that ONE syntactic structure selected & maintained [Serial Account]? –Such findings do rule out full parallelism/delayed interpretation

26 Syntactic Parallelism Debate Serial accounts must explain why some re-analyses are costly and some are not. –The horse raced past the barn… fell. –Ron believes Rex …is a threat. [Pritchett, 1992] –Reanalysis costs linked to similarity of potential analyses or informativeness of disambiguating cue [Abney, 1989; Fodor & Inoue, 1994; Konieczny, 1996; Lewis,1998, Pritchett, 1992] Ranked parallelism w/costs for re-ranking [Gibson, 1991; Gorrell, 1987; Hickok, 1993; Tabor & Hutchins, 2004] –Re-ranking costs predicted by… Relative support for each analysis “Digging in” effects (Tabor & Hutchins, 2004) Distinguish between Serial+Reanalysis accounts & Limited, Ranked Parallel accounts

27 Hsieh et al. Paper Sharon & Lucy

28 Hagoort (2008) Is brain imaging of use for cognitive theory? –Fodor: does not help to know it happens somewhere north of the neck –Critics focus on fmri Cog Neuro toolkit includes ERP & MEG, TMS Should we be interested in the machinery that instantiates human language, or just cognitive architecture? How does ERP research support the Immediacy Assumption (all types of info brought to bear immediately)?

29 Syntactic & Semantic Processing Structure and Interpretation co-vary: –Put (the book) (in the box on the table). –Put (the book in the box) (on the table). Does structural analysis necessarily license interpretation?

30 Syntactic & Semantic Processing in Tandem Constraint-based Lexicalist models (e.g., MacDonald et al., 1994) Boland’s Concurrent model (1997) Kuperberg (2007) The thief (who was) searched by the police had weapons. [good agent, infreq participle] The award (that was) accepted by the man was impressive. [poor agent, freq participle] Initial attachment of verb to PS tree is influenced by thematic fit and frequency of alternative verb forms

31 Boland’s Concurrent Theory award -Theme accepted Agent accepted … Theme accepted … (by…) Accepted –active, past Accepted –passive, participle The award accepted…

32 Syntactic Primacy Theories Frazier’s Garden Path model (1978 & later) Friederici’s 3-Stage Model (e.g., 2002) 1.Attach each new constituent to developing phrase structure tree 2.Lexico-semantic processing & thematic role assignment 3.Syntactic integration & revision Trueswell’s ‘good agent/freq participle’ condition would have an advantage here

33 Testing Parsing Theories To what extent does semantic interpretation depend upon successful syntactic analysis?

34 Primacy of Syntactic Processing Friederici & Weissenborn (2007, p. 54) “ semantic integration of words does not take place for words which are not syntactically licensed (have wrong word category). ” Investigate with ERP ’ s, because different components elicited by syntactic & semantic anomalies. A syntactic category violation … Der Priester wurde vom *gebaut … The priest was by-the *built … [read German/French sentence, then judge acceptability] … elicits a LAN, followed by a P600, but no N400 effects (Friederici et al., 1999, 2004; Hahne & Friederici, 2002, Experiment 1; Hahne & Jescheniak, 2001; Isel et al., 2007)

35 Boland’s Concurrent Theory Der Priester wurde vom *gebaut The priest was by-the * built … vom [Agent]

36 Counter-evidence ? Ainsworth-Darnell, Shulman, & Boland (1998) entrusted: Control:Jill entrusted the recipe to friends… Syntactic Anomaly:Jill entrusted the recipe friends… P600 Semantic Anomaly:Jill entrusted the recipe to platforms… N400 Double Anomaly:Jill entrusted the recipe platforms… N400 + P600

37 Is Syntactic Primacy Universal? Zhang, Yu, & Boland (under revision) In German, syntactic category is well-marked (nouns capitalized, case- markings on determiners and adjectives, verb tense affixes, agreement morphology, etc.) Der Priester wurde vom Arbeiter. (expected N) Der Priester wurde vom gebaut. (ungrammatical V) N400 observed if told to focus on meaning of sentence In Chinese, syntactic category is not marked by morphology on the words themselves 李薇把新鲜的鸭梨慢慢地削了两个。 (expected V “ peeled ” ) 李薇把新鲜的鸭梨慢慢地刀子了两个。 (ungrammatical N “ knife ” ) Some theories assume syntactic primacy (e.g., Frazier, 1978, Friederici, 2002), others do not (e.g., Boland, 1997; Kuperberg, 2007; MacDonald et al., 1994).

38 Could Syntactic Primacy be a LG-specific strategy? Strongest evidence for Syntactic Primacy comes from German. In German, syntactic category is well-marked (nouns capitalized, case- markings on determiners and adjectives, verb tense affixes, agreement morphology, etc.) Der Priester wurde vom Arbeiter … (expected N) Der Priester wurde vom gebaut … (ungrammatical V)  N400 is observed if told to focus on meaning of sentence Zhang, Yu, & Boland (under revision) In Chinese, syntactic category is not marked by inflectional morphology on the words themselves 李薇把新鲜的鸭梨慢慢地削了两个。 (expected V “ peel ” ) 李薇把新鲜的鸭梨慢慢地刀子了两个。 (ungram N “ knife ” )

39 Stimuli & Results Correct 女孩 / 买 / 了 / 裙子 / 和 / 手套。 The girl/ bought/ le (PERF)/ skirt/ and/ glove. (The girl bought a skirt and a glove.) Syntactic violation LAN + P600 女孩 / 买 / 了 / 很 / 裙子 / 和 / 手套。 The girl/ bought/ le (PERF)/ very/ skirt/ and/ glove. (The girl bought a very skirt and a glove.) Semantic violation N400 女孩 / 吃 / 了 / 裙子 / 和 / 手套。 The girl/ ate/ le (PERF)/ skirt/ and/ glove. (The girl ate a skirt and a glove.) Syntactic & Semantic violation LAN + P600 & N400 女孩 / 吃 / 了 / 很 / 裙子 / 和 / 手套。 The girl/ ate/ le (PERF)/ very / skirt/ and/ glove. (The girl ate a very skirt and a glove.) PERF = perfective marker Critical word in bold. Suggests that syntactic & semantic processing go on in parallel

40 Manipulate degree of Semantic violation at syntactic anomaly Larger N400 for strong semantic violation compared to weak semantic violation, despite syntactic anomaly

41 Difference Map Showing the Scalp Distributions of the Strong-Weak Effects View of top of head; the anterior is on top

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44 Ye, Luo, Friederici, & Zhou (2006) N400 sustained anterior negativity (no P600) + “N400-like effect” “ba” construction; auditory

45 Summary Across LGs English evidence is mostly consistent with syntactic & semantic processing in tandem French & German readers switch between “syntactic primacy” mode & “interpret anyway” mode, depending on instructions. Chinese stay in “interpret anyway” mode. –Can you force Chinese (or English) readers into “syntactic primacy mode”? –Does Chinese lead to a greater reliance on semantic processing than German? No reason to favor sentence processing theories that maintain syntactic primacy.


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