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Sentence Processing 1: Encapsulation 4/7/04 BCS 261.

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Presentation on theme: "Sentence Processing 1: Encapsulation 4/7/04 BCS 261."— Presentation transcript:

1 Sentence Processing 1: Encapsulation 4/7/04 BCS 261

2 Themes for today Discuss some basic principles of processing sentences (Tanenhaus) Discuss some evidence for a modular/serial parser (Rayner et al.)

3 Sentence Processing The goal of sentence processing is to understand the representations people form as they understand a sentence (syntax, meaning…).

4 Immediacy Processing is incremental Methods Monitoring tasks (phoneme, word, etc…) Probing and priming tasks Self-paced reading Eye fixations in reading (and in the visual world) ERPs

5 Ambiguity Syntactic ambiguities are the main object of study. The spy saw the cop with telescope. Why?

6 Ambiguities For a dishonest employee Her true ability was deceiving. For a stupid employee I most enthusiastically recommend this candidate with no qualifications whatsoever. For the office drunk He generally found himself loaded with work to do.

7 Structuring Input The horse… The hoarse (singer)… The horse race... The horse raced... The horse raced past the barn… The horse raced past the barn fell. What’s the difference between serial and parallel?

8 Classes of theories Parallel / Modular multiple structures computed using a single source of information Serial / Modular One structure is computed at a time using a single source of information Parallel / Interactionist Multiple structures are computed using multiple sources of information Serial / Interactionist One structure is computed at a time using multiple sources of information Parallel Serial Modular Inter.

9 Classes of theories Modular Models- restricted domain of information plays an initial role in parse (syntax) (Frazier, Rayner, Clifton). Constraint Based Models- information from a variety of domains plays a role in structuring sentence (Tanenhaus, Trueswell, MacDonald, Seidenberg).

10 Constraints Computational resources Lexical constraints The raft floated down the river sank. The salmon released in the stream spawned. Frequency Discourse and Pragmatic Context “The horse raced past the barn fell.” “A horse was raced past a field and another horse raced past a barn. The horse raced past the barn fell.” What are some other possible constraints? How could we test them?

11 Computational Models A computational model is a formal model that could be implemented on a computer and is meant to mimic some aspect of behavior (1) Gibson has an explicit model of processing difficulty (2) Probabilistic models of processing (Jurafsky) (3) SRNs (Elman, Christiansen, Tabor) Very few computational models of sentence processing. Why? Is it a simple problem or a hard one? (anthony) Is it useful to create computational models? Why?

12 Discussion Questions Since humans get garden-pathed, is the parsing system flawed? (nicole) Does it make sense to build a machine that parses exactly the way a human does? What would be some advantages? Disadvantages? Marslen-wilson claims that the modality of the stimulus affects processing. Can we assume that models of reading and listening are the same? (Jessica, Beth)

13 Rayner, Carlson, & Frazier Central Question: How does pragmatics interact with parsing choices? Interactive view: Marslen-Wilson (1975) Autonomous model: Forster (1979) – rules are in different subsystems, no feedback from semantic or message-level processors to lexical or syntactic analysis

14 Garden Pathing The performer sent the flowers... The phrase sent the flowers is ambiguous.

15 The Debate “The central issue in the debate between autonomy and interaction in processing is not whether all relevant types of information can be exploited at some point in the comprehension of a linguistically conveyed message.” What is the central issue?

16 Integration Rayner and colleagues point out that there is probably integration of information between levels before the complete representation is computed. Why would this integration be helpful? In some cases,integrating information would not be useful.

17 Hypothesis They take an intermediate position between extreme modularity and extreme interactionism: Initial analyses are syntactic but interaction occurs in later stages. Minimal Attachment Weak Semantic Principle

18 Distinguishing Theories Minimal Attachment and Weak Semantic Principle- in ambiguous sentences, people prefer the interpretation with the fewest syntactic nodes. Crain and Coker -Crain and Coker: is it rejecting semantic anomaly or preferring pragmatic plausibility?

19 Crain and Coker a) The florist sent the flowers b) The performer sent the flowers. Reduced Relative interpretation 16% in (a) 42% in (b) Is this pattern problematic for Minimal Attachment? Why aren’t Rayner et al. convinced by this data?

20 On-line Reading Experiments Experiment 1 - pragmatics does not play a role in initial structuring (syntax). Experiment 2 - pragmatic and semantic information eventually effects a parse.

21 Experiment 1 (a) The florist sent the flowers was very pleased (reduced implausible). (b) The performer sent the flowers was very pleased (reduced plausible). (c) The performer who was sent the flowers was very pleased (unreduced plausible). (d) The performer sent the flowers and was very pleased with herself (active implausible). What are the predictions? Is (a) really implausible? (beth, nicole) What are some better ways to create implausible stimuli?

22 Eye tracking and reading Garden Path- elevated reading times and looks to previous word on the disambiguating region: Ex. The florist sent the flowers was very pleased Disambiguating word

23 Results Paraphrase- More relative clause interpretations in the reduced plausible condition. Reading Data- Reading time was slower in both reduced conditions at disambiguating region. There are also more regressions.

24 Discussion Garden Path effects in both reduced conditions, suggesting syntax only structuring in the initial stages. May have gotten an effect with more extreme plausibility differences. Next Question: What role does pragmatics play in parsing?

25 Pragmatics and Parsing Rayner claims that Experiment 1 shows that not all possible parses of a sentence are computed. Why? Pragmatics can’t be used as a filter. Pragmatics could compute all the relations between elements in a sentence and then match with syntax’s interpretation. Problems?

26 Thematic Selection Hypothesis Get info about thematic structure that’s associated with the verb to constrain the relations that are considered. Jonn slept (experiencer) John saw the lunar eclipse (experiencer, theme) John saw the lunar eclipse with the telescope, (experiencer, theme, instrument) If the most plausible interpretation conflicts with the syntactic analysis, the person has to reanalyze.

27 Experiment 2 Stimuli (a) The spy saw the cop with the binoculars but the cop didn’t see him. (b) The spy saw the cop with the revolver but the cop didn’t see him. What are the predictions? Potential explanation based on frequency? What are the problems with comparing just these two sentences?

28 Results Reading time and fixation duration longer in the non-minimal attachment sentences.

29 Discussion How might an interactionist respond to this data? Are there any alternative explanations? When we hear language, it’s usually in some sort of context. How might this effect these results? What sort of concerns might we have about the claim that eye-tracking is a window into initial processing?

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