An Electrophysiological
Investigation of the
Effects of Coreference
on Word Repetition
and Synonymy
Jane E. Anderson & Phillip J.
Holcomb
2005
Presented by Dora Lu for Psych593SG
Coherent Speech…
How to relate new and old
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 study
• How the neural system underlying text
comprehension 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 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: ERP
Repeated items:
• Attenuation of the N400
• The augmentation of a subsequent
late positive component (LPC)
LPC (Rugg 1987)
Semantic 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
unrelated prime word preceding the same
target word.
dog……cat vs. pan……cat
- Semantic priming does not results in an
enhancement of the subsequent LPC
Priming Effect
• Why smaller N400?
- Reflect the ease of
integrating the
semantic
information
activated by a
primed word
(Holcomb 1993)
Priming Effect
-The late positive
component (LPC)
reflects a larger
discrepancy
between the
baseline familiarity
of low frequency
words and their
high experimental
familiarity (Rugg,
1990)
Repetition Effect in longer
texts
• 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 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 processing
• N400 for discourse anomalies
(Van 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 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
noun phrases:
• Behavioral:
Irwin et al. (1982):
-Repeated words were faster than not repeated
words
-Words preceded by the definite article were
responded even faster
definite article provides a cue for old information
and this facilitates its processing
Murphy (1984):
-RTs for sentences containing definite article are
faster than sentences containing indefinite article.
 Finding the antecedent for a definite reference is
easier than establishing a new referent.
However, these behavior
studies cannot tell us…
• On-line comprehension process.
• Lexical decision task may encourage
people to adopt unnatural sentence
processing strategies.
• Lexical decision task doesn’t allow
people to examine the repetition and
coreference effects in longer contexts.
Current Study
Repetition 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.
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.
Predictions
If N400 is also sensitive to coreference (a
discourse factor), then….
• For repetition priming condition:
-stronger repetition effects for words
preceded by the definite article.
Greater attenuation of the N400
• For semantic priming condition:
-similar as repetition effects but to a lesser
degree
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.
Predictions
If N400 is primarily sensitive to lexical/sentential
processes, 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
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.
Predictions
Sentence final words…
Osterhout & Holcomb (1992):
sentence final words from sentences
that are semantically difficult to
interpret have larger N400.
sentences with indefinite article
should have larger negativity.
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.
Summary of
predictions:
Component
Target
Word
The cab
N400
discourse
smaller
A cab
Larger
Final
word
Larger
lexical
LAN
WM
load
Same
Larger
amount of
attenuation
for indefinite
sentences
smaller
Integration
smaller
Larger
Others
Processing
difficulties
could be
indexed by
both
N400 + LAN
Experiment 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: Stimuli
Experimental (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: Stimuli
Experimental (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 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: procedure
500ms
500ms
+
345ms
70ms
The
345ms
70ms
cab
70ms
……
1500ms
345ms
car
Yes or No
Respond
now
Comprehension
question
2000ms
Respond now
Yes or No
Experiment 1:
Data
• Data recording: 13 locations, referenced to
left mastoid.
• Data analysis:
-time locked to articles
-time locked to the critical noun
-time windows
(P2, N280)(N400, N400-700)
onset
(critical word N400, LAN)
150ms 300 450 600 750
900 1050 1200 1350ms
(400-700, 700-1100ms for final word)
Experiment 1: Results
a) The cab came very close to hitting a car.
b) A cab came very close to hitting a car.
Experiment 1: Results
a) The cab came very close to hitting a car.
b) A cab came very close to hitting a car.
Experiment 1: Results
a) The cab came very close to hitting a car.
b) A cab came very close to hitting a car.
Experiment 1: Results
a) The cab came very close to hitting a car.
b) A cab came very close to hitting a car.
Experiment 1: Results
• If time-locked to article:
150-300ms
300-600ms
Indefinite
Indefinite more
more negative negative, anterior
distribution
7151015ms
Final word
(400-700,
700-1100)
No
differences
no
differences
• If time-locked to critical noun:
Between 300-600ms, words following
definite article were more negative
Experiment 1: discussion
• Both articles elicited N280 and N400700, 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
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
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.
foreperiod
Warning
stimulus
Imperative stimulus
respond
Why greater negativity for
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: 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: Stimuli
Experimental (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: procedure
500ms
+
500ms
345ms
70ms
The
345ms
(SOA:415ms)
70ms
cab
345ms
70ms
……
370ms
car
Next
word
(SOA:715ms)
……
Last
word
Yes or No
1500ms
Respond now
Experiment 2 results: article effects (150-300ms)
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 (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)
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)
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 effect
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.
• Effects of repetition
and semantic
priming: repeated
words are less
negative.
Experiment 2: priming effect
Kathy 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: 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 effect
Joanne 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: results
• The priming effect was not modulate
by coreferential status.
Experiment 2: results
• Final word: negative-going component onset at about
300ms. Waveforms start diverging around 400ms and last
throughout.
• In 400-700ms window, main effect of coreferential status.
Indefinite sentences more negative. Larger effect at central
and posterior sites.
Discussion: comparison of
exp1 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.
Discussion
• Priming effects were not modulated by the
coreferential 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
negativities.
 Coreferential effects elicited LAN.
LAN
• 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
assignment 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 exp2
a) The cab came very close to hitting a car.
b) A cab came very close to hitting a car.
Final word effects
a) The cab came very close to hitting a car.
b) A cab came very close to hitting a car.
Final word effect
• Non-coreferential sentences are more
negative.
• Not shown on the critical noun, but could
be a delayed effect, because they have
similar distribution to the N400 (centralparietal).
• This effect could reflect difficulty in
integrating the meaning of sentences that
began with indefinite article. Coreferential
trials are more coherent than the noncoreferential ones.
LPC
• No LPC found. Why?
-words in this study were not low in
frequency
-rapid presentation rate in this study
precluded the presence of late
positivity.
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.
Summary:
Component
Target
Word
The cab
N400
discourse
smaller
A cab
Larger
Final
word
Larger
lexical
LAN
WM
load
Same
Larger
amount of
attenuation
for indefinite
sentences
smaller
Repetition
effect
Integration Larger N400
smaller
Larger
for repeated
words, and
this effect
extended to
a discourse
level.
Thank you!
Questions to
Susan or me?
Comments?
Questions
• 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?