an electrophysiological investigation of the effects of coreference on word repetition and synonymy...

An Electrophysiological InAn Electrophysiological Investigation of the Effects ovestigation of the Effects of Coreference on Word Repf Coreference on Word Rep

etition and Synonymyetition and Synonymy

Jane E. Anderson & Phillip J. Jane E. Anderson & Phillip J. HolcombHolcomb

20052005

Presented by Dora Lu for Psych593SGPresented by Dora Lu for Psych593SG

Coherent Speech…Coherent Speech…

How to relate new and old How to relate new and old information?information?

(1a) The truck rolled into a ditch as the driver was flagging down a passing car.

• Noun repetition(2a) The truck had a bad parking brake.

• Synonym(2b) The vehicle had a bad parking brake.

• Anaphors: pronouns(2c) It had a bad parking brake.

Goals of this studyGoals of this study• How the neural system underlying text compr

ehension use ‘noun repetition’ and ‘synonym’ to refer to a previously mentioned instance.

- repetition and semantic priming effect (lexical/semantic memory effects or a discourse factor)

- coreferential effect elicited by definite and indefinite article

Repetition EffectRepetition Effect• Robust in lexical

decision, word identification and naming tasks

-Behavioral: words are processed faster and more accurately when they are preceded by an earlier presentation of the same word

From Scarborough et al. (1977)

Repetition Effect: ERPRepetition Effect: ERPRepeated items:• Attenuation of the N400• The augmentation of a subsequent

late positive component (LPC)

LPC (Rugg 1987)LPC (Rugg 1987)

Semantic Priming EffectSemantic Priming Effect• Behavioral: when a target word is preceded by

a semantically related priming word, RTs are shorter

dog……cat• ERP: - the N400 is attenuated if compared to an unrel

ated prime word preceding the same target word.

dog……cat vs. pan……cat- Semantic priming does not results in an enhan

cement of the subsequent LPC

Priming EffectPriming Effect• Why smaller N400?- Reflect the ease of

integrating the semantic information activated by a primed word (Holcomb 1993)

Priming EffectPriming Effect-The late positive com

ponent (LPC) reflects a larger discrepancy between the baseline familiarity of low frequency words and their high experimental familiarity (Rugg, 1990)

Repetition Effect in longer Repetition Effect in longer textstexts

• Van Petten et al (1991): reading texts from Readers’ Digest -Found ERP repetition effects during text processing.-Opposite results: Larger LPC for not repeated words

N400 and global processingN400 and global processing

• St. George et al. (1989): N400 to content words was larger when the paragraph was not coherent (i.e. paragraph did not have a title)

N400 and global processingN400 and global processing• N400 for discourse anomalies (V

an Berkum et al 1999)

As agreed upon, Jane was to wake her sister and her brother at five o’clock. But the sister had already washed herself and the brother have even got dressed.

a) discourse-coherent: Jane told the brother that he was exceptionally quick.

b) discourse-anomalous: Jane told the brother that he was exceptionally slow.

• The N400 to the discourse anomaly had a similar time course, distribution and morphology compared to the N400 elicited by a local anomaly.

N400 and global processingN400 and global processing• Subsequent definite noun elicited a

more negative-going waveform compared to when there was only one potential referent (Van Berkum et al 1999).

One referent: David had told the boy and the girl to clean up their room before lunch time. But the boy had stayed in bed all morning, and the girl had been on the phone all the time.

Two referents: David had told two girls to clean up their room before lunch time. But one of the girls had stayed in bed all morning, and the other had been on the phone all the time.

David told the girl that there will be some vistors.

• These effect have been replicated in auditory modality as well (Van Berkum et al 2003)

Processing of definite/indefinite Processing of definite/indefinite noun phrases:noun phrases:

• Behavioral:Irwin et al. (1982):-Repeated words were faster than not repeated words-Words preceded by the definite article were responded

even fasterdefinite article provides a cue for old information and

this facilitates its processing

Murphy (1984):-RTs for sentences containing definite article are faster t

han sentences containing indefinite article. Finding the antecedent for a definite reference is easi

er than establishing a new referent.

However, these behavior However, these behavior studies cannot tell us…studies cannot tell us…

• On-line comprehension process.• Lexical decision task may encourage pe

ople to adopt unnatural sentence processing strategies.

• Lexical decision task doesn’t allow people to examine the repetition and coreference effects in longer contexts.

Current StudyCurrent StudyRepetition priming condition:Kathy sat nervously in the cab on her way to the

airport.a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Synonym (semantic) priming condition:Kathy sat nervously in the taxi on her way to the

airport.a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

PredictionsPredictionsIf N400 is also sensitive to coreference (a discour

se factor), then….

• For repetition priming condition:-stronger repetition effects for words preceded b

y the definite article.Greater attenuation of the N400

• For semantic priming condition:-similar as repetition effects but to a lesser degre

e

Kathy sat nervously in the cab on her way to the airport.a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

PredictionsPredictionsIf N400 is primarily sensitive to lexical/sentential process

es, then….

• Equivalent N400 attenuation for words following definite and indefinite articles.

• May have other ERP components that are sensitive to coreference (i.e. LAN).

repeated and synonym noun phrases following definite articles should produce a larger LAN.

the indefinite noun phrases will have a larger LAN, because they are harder to integrate

processing difficulties may be indexed by N400, LAN or other components


PredictionsPredictionsSentence final words…Osterhout & Holcomb (1992): sentence fin

al words from sentences that are semantically difficult to interpret have larger N400.

sentences with indefinite article should have larger negativity.


Summary of Summary of predictions:predictions:

Component

Target Word

N400 LAN Othersdiscourse lexical WM

loadIntegration Processing

difficulties could be

indexed by both

N400 + LANThe cab smaller Same amount of

attenuation

Larger smaller

A cab Larger smaller Larger

Final word

Larger for indefinite sentences


Experiment 1Experiment 1• A control study to verify…

-the differences they found are not due to the inherent (physical/lexical) differences between ‘The’ and ‘A’

-determine the ‘carry-over’ effect

Experiment 1: StimuliExperiment 1: StimuliExperimental (repetition)-Kathy sat nervously in the cab on her way to the airport.a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Experimental (synonym)-Kathy sat nervously in the taxi on her way to the airport.a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Filler:-Joanne had just won her bet at the horse races. She waited in line to get 75 dollars.

Anomaly:-Joshua was riding on his bus to school one morning. A bus was stalled at the butter

Experiment 1: StimuliExperiment 1: StimuliExperimental (120)-Kathy sat nervously in the cab on her way to the airport.a) The cab came very close to hitting a car. (60)b) A cab came very close to hitting a car. (60)

Experimental (synonym)-Kathy sat nervously in the taxi on her way to the airport.a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Filler: (30)-Joanne had just won her bet at the horse races. She waited in line to get 75 dollars.

Anomaly: (30)-Joshua was riding on his bus to school one morning. A bus was stalled at the butter

Experiment 1Experiment 1• Participants: 24• Procedure: -central presentation, one word at a

time-determine sentences are good or

anomalous-A rest break after 30 trials. 4

true/false comprehension questions at each break.

Experiment 1: procedureExperiment 1: procedure+

500ms

The345ms

500ms

cab345ms

Comprehension question

……

70ms

70ms

Respond now

car

70ms

1500ms

Respond now

345ms

Yes or No

2000ms

Yes or No

Experiment 1: Experiment 1: DataData

• Data recording: 13 locations, referenced to left mastoid.

• Data analysis:-time locked to articles-time locked to the critical noun-time windows

onset150ms 300 600450 750 900 1050 1200 1350ms

(P2, N280) (N400, N400-700) (critical word N400, LAN)

(400-700, 700-1100ms for final word)

Experiment 1: ResultsExperiment 1: Resultsa) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Experiment 1: ResultsExperiment 1: Results• If time-locked to article:

• If time-locked to critical noun:Between 300-600ms, words following

definite article were more negative

150-300ms 300-600ms 715-1015ms Final word (400-700, 700-1100)

Indefinite more negative

Indefinite more negative, anterior distribution

No differences

no differences

Experiment 1: discussionExperiment 1: discussion• Both articles elicited N280 and N400-700,

typical pattern for closed class words.• Words following the indefinite article ‘

A’ were more negative over the anterior cites.

not coreference, but due to the lexical function of the articles.

Why greater negativity for Why greater negativity for the indefinite article?the indefinite article?

• The indefinite article reflects the anticipation of ‘new’ information. This might relate to the contingent negative variation (CNV). (Van Petten and Kutas 1991)

Contingent negative Contingent negative variation (CNV)variation (CNV)

• Chronometric paradigm: paired-stimulus. • CNV: a slow negative component that develops

between a warning stimulus and a subsequent imperative stimulus.

• Usually observed when subjects performed a task requiring motor responses. Reflecting the anticipation or preparation for incoming information.

Warning stimulus

Imperative stimulus

foreperiod

respond

Why greater negativity for Why greater negativity for the indefinite article?the indefinite article?

• There is a preference for the definite article at the beginning of sentences and for the indefinite article in the object position (Yekovich et al. 1979)

• The difference is due to the physical attributes of the articles. Word length is a predictor of negativity (Osterhout et al 2002).

• Word length and CNV: indefinite article was accessed in less time, given more time to anticipate the next word, which results in an enhanced CNV.

Experiment 1: discussionExperiment 1: discussion• Time locked to article, no differences

in the ERPS to critical nouns following the articles no carry over

• Conditions do not differ in final word article differences in the beginning of the sentence do not affect sentence wrap up effect

Experiment 2: StimuliExperiment 2: StimuliExperimental (repetition) (60)-Kathy sat nervously in the cab on her way to the airport.a) The cab came very close to hitting a car. (30)b) A cab came very close to hitting a car. (30)

Experimental (synonym) (60)-Kathy sat nervously in the taxi on her way to the airport.a) The cab came very close to hitting a car. (30)b) A cab came very close to hitting a car. (30)

Filler: (30)-Joanne had just won her bet at the horse races. She waited in line to get 75 dollars.

Anomaly: (30)-Joshua was riding on his bus to school one morning. A bus was stalled at the butter

Experiment 2: procedureExperiment 2: procedure+

500ms

345ms

500ms

345ms

70ms

70ms

70ms

370ms345ms

1500ms

Yes or No

(SOA:715ms)

The

cab

……

carNextword

(SOA:415ms)

……Lastword

Respond now

Experiment 2 results: article effects (150-300ms)Experiment 2 results: article effects (150-300ms)


Experiment 2 results: article effects (300-600ms)Experiment 2 results: article effects (300-600ms)Kathy sat nervously in the cab on her way to the airport.

a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Experiment 2 results: article effects (715-1015ms)Experiment 2 results: article effects (715-1015ms)


Experiment 2 results: article effects (715-1015ms)Experiment 2 results: article effects (715-1015ms)Kathy sat nervously in the cab on her way to the airport.

a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Experiment 2: priming effectExperiment 2: priming effect

• Effects of repetition and semantic priming: repeated words are less negative.

Kathy sat nervously in the cab on her way to the airport. (repetition)Kathy sat nervously in the taxi on her way to the airport. (synonym)

A/The cab came very close to hitting a car.

Experiment 2: priming effectExperiment 2: priming effectKathy sat nervously in the cab on her way to the airport. (antecedent)Kathy sat nervously in the taxi on her way to the airport. (antecedent)

a) The cab came very close to hitting a car. (repetition)b) A cab came very close to hitting a car. (synonym)

Experiment 2: ResultsExperiment 2: Results• The N400 amplitude of content words declines

with increasing sentence position, reflecting the build-up of contextual constraints. (Van Petten & Kutas 1990)

• The declination has not been found with longer texts (Van Petten 1995)

• So, what does the smaller N400 for repeated and synonym words mean? Larger build-up of context?

Experiment 2: priming effectExperiment 2: priming effectJoanne had just won her bet at the horse races. (filler)

a) The cab came very close to hitting a car. (repetition)b) A cab came very close to hitting a car. (synonym)

Experiment 2: resultsExperiment 2: results

• The priming effect was not modulate by coreferential status.

Experiment 2: resultsExperiment 2: results• Final word: negative-going component onset at about 300ms. Wa

veforms start diverging around 400ms and last throughout.• In 400-700ms window, main effect of coreferential status. Indefin

ite sentences more negative. Larger effect at central and posterior sites.

Discussion: comparison of Discussion: comparison of exp1 and exp2exp1 and exp2

• Indefinite article ‘A’ elicited a greater N400-700 than the definite article ‘The’ with (exp2) or without (exp1) context. processing differences even when the definite article ‘the’ does not explicitly refer to given information.

• The greater negativity of indefinite article could be reflecting the anticipation of the upcoming noun. But not sure if this is due to discourse factors, word length or other factors.

• No P2 found in exp2. This could be a carry-over effect in exp1, or this is an exogenous component related to word size. Subjects read a lead-in sentence in exp2.

• Found repetition/semantic priming effects (N400 attenuation) across sentence boundary.

DiscussionDiscussion• Priming effects were not modulated by the coreferen

tial status. Why?-the priming effects are so strong that they obscure the weaker coreference effect.

• Coreferential effect: different than N400 in:1) distribution. Greater negativity over left anterior and

temporal sites to coreferential words (definite).2) Opposite polarity. Coreferential items have larger ne

gativities. Coreferential effects elicited LAN.

LANLAN• Elicited by syntactic violations (Osterhout & Holcomb 1992)But coreference is not a syntactic anomaly.

• Elicited by the increasing demands on working memory. (King & Kutas 1995)• LAN to verbs in object relative sentences. Thematic role assignm

ent is a harder process in object relative clauses. The head noun must be reactivated to be assigned and which increases working memory load.

The reporter who the senator harshly attacked admitted the error.The reporter who harshly attacked the senator admitted the error.

• For the definite article, the referential assignment causes an increase in the working memory load.

Correferential effects: LAN in exp2Correferential effects: LAN in exp2a) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Final word effectsFinal word effectsa) The cab came very close to hitting a car.b) A cab came very close to hitting a car.

Final word effectFinal word effect• Non-coreferential sentences are more negativ

e.• Not shown on the critical noun, but could be a

delayed effect, because they have similar distribution to the N400 (central-parietal).

• This effect could reflect difficulty in integrating the meaning of sentences that began with indefinite article. Coreferential trials are more coherent than the non-coreferential ones.

LPCLPC• No LPC found. Why?-words in this study were not low in freque

ncy-rapid presentation rate in this study precl

uded the presence of late positivity.

Summary:Summary:

Component

Target Word

N400 LAN Repetition effect

discourse lexical WM load

Integration Larger N400 for repeated words, and this effect

extended to a discourse

level.The cab smaller Same amount of

attenuation

Larger smaller

A cab Larger smaller Larger

Final word

Larger for indefinite sentences


Thank you!Thank you!

Questions to Susan or me?

Comments?

QuestionsQuestions• Compare the repetition and synonym with the

first content word of the fillers. No fixed position and word classes?

• The ‘antecedents’ in the first sentence always preceded by the definite article. It somehow makes the indefinite NP in the beginning of the second sentence less preferable. Would it be better to manipulate the articles in the first sentence too?

an electrophysiological investigation of the effects of coreference on word repetition and synonymy...

Documents

word repetition

target word

related priming word

word identification

title n400

discourse anomaly

lunch time

erp repetition effects