Handedness, hemispheric asymmetries, and joke comprehension

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Handedness, hemispheric
asymmetries, and joke
comprehension
Seana Coulson, Christopher Lovett
Marianna’s question
My questions this week concern the tests administered to the
participants in order to classify them into groups.
First, regarding the handedness assessment test, the authors
mention that the handedness scale ranges from -100 to +100
(completely left-handed to completely right-handed respectively).
Their groups of participants seem to be unbalanced along this scale
(left-handers: -51, right-handers: +71). Is this an important
difference? Could this affect the results in any way? At some point,
in the results discussion, they mention that some of the left-handed
women had left-handed relatives. Is this included in this
handedness assessment test?
I was also interested in knowing more about the semantic relation
test they used to determine participants' verbal ability. What does
this test consist in? Is it a typical test administered to determine
verbal ability scores? Why do women perform so poorly?
Lynn’s question
• The experimenters presented a comprehension
question at the end of each stimuli sentence. They
do not report (or perhaps did not record) the
reaction time it took the participants to answer the
comprehension questions. If they had reported
reaction times to the questions would speed of
processing diffferences been revealed between
right and left handers, or males and females or
between the high and low vocabulary groups? It
would be helpful to see if some kind of behavioral
measure correlated to the ERP results they report.
Albert’s question
• Understanding jokes is as easy as understanding the N400 component.
I quote from page 281-282, "Typical of ERPs to visually presented words,
all stimuli elicited N1, P2, and N400." I might be misunderstanding this
but this seems to say that all words elicit an N400. What I am missing?
Our general understanding of the N400 component is that there is a large
negativity around 300-500 ms in response to a word which is syntactically
appropriate but not semantically appropriate. I think that their stimuli
was trying to elicit the N400 on the Joke set and the Straight set but not
the Expected set of sentences. The graphs seem to indicate that there is a
N400 for most of the Jokes and Straights. The authors seem to be
surprised that the N400 was larger for the Joke set only for subjects with
low verbal ability (Previous research suggested so).
Pawel’s question
•
The authors say that a possible reason for the differences for
handedness and sex are due to unequal corpus callosal areas. Might
a
half-field ERP study be a good way to test this claim? The sentence
final
word that determines if a sentence is a joke or not could be
lateralized and
then the responses for LVF/RH and RVF/LH for each each type of
handedness/sex could be compared to each other. So, could this
flesh out
whether the differences observed were due to inter-hemispheric
transfer or
inherent hemispheric asymmetry?
Israel’s question
•
Hi everyone,
Here are my questions/comments on this week's article:
In the data analysis, the authors say that they rejected artifacts such as ?excessive muscle activity?.
Does this "activity" refer to laughter, since we are dealing with joke comprehension? In the same
line, isn't laughter such a big artifact that it could potentially ruin a large proportion of the trials?
Another issue related to joke comprehension is that there may be variability among participants
regarding what they find funny. That is, they may understand that the sentence they are presented
with is a joke, yet they may not find it funny. Would we expect a different reaction to jokes that are
perceived as funny and those that aren't?
Finally, I had trouble understanding how they decided, from the comprehension questions, whether
people understood the jokes or not. The example they gave is:
??Every time I wear my spring coat in the rain, it damages the springs.??
Comprehension sentence: ??Water isn?t good for my coat.??
Correct response: YES.
I don't see how they need to understand the joke in order to answer this question, they could
simply be relying on general world knowledge (e.g. Rain is not good for coats).
See you on Tuesday!
Israel
Introduction
• Lateralization: despite anatomical similarity,
hemispheres play different roles in language
production and comprehension.
• Evidence from aphasics & experimental studies:
– LH: basic aspects of production and comprehension
– RH: social appropriateness monitoring, tangential
speech, nonverbal cues, overly literal interpretation,
sarcasm, inference in joke comprehension
Handedness and hemispheric asymmetry for
language
•
•
•
•
This pattern presupposes right-handedness (90%)
Broca assumed pattern would be reversed in LH
In reality, LH more likely to display “atypicality”.
Wada test
– RH: 92 – 99% LH dominant for language
– LH: 85% LH, 15% RH/Bilateral
• fMRI
– RH: 96% LH, 4% RH
– LH: 76% LH, 10% RH, 14% Bilateral
• rTMS
– RH: 87.5% LH 4.2% RH, 8.2% Bilateral
– LH: 73.7% LH, 10.5% RH, 15.8 Bilateral
Knecht et al (2000) found near linear relationship between the degree of
handedness (Edinburgh Inventory) and language lateralization (transcranial
Doppler sonography) during a word generation task. RH dominance more likely
in LH, and those with at least one LH parent.
Handedness and ‘right hemisphere’
language processes
• Handedness impacts fundamental processes such as production and
comprehension.
• What about high level language processing?
– Joke processing requires constructing mental model and then “frame-shifting”
to undergo a semantic reanalysis
– Difficulty with joke comprehension associated with RH damage
• Kutas & Coulson (2001) found left lateralized sustained negativity (500-900
ms), N400, and later posterior positivity in people who got most of the
jokes.
– If N400 reflects processing difficulty, why not found in the people who didn’t
get the jokes?
• People with poor comprehension: only right frontal negativity (300-700
ms) to jokes.
ERP effects tended to be lateralized, suggesting contributions of one
hemisphere more important
Present study
• Investigate the consequences of bilateral
language representation in processing of jokes
(thought to recruit right hemisphere in RH)
• Record ERPs as left & right handers read one-line
jokes
• Hypothesis:
– If LH brains are more laterally symmetric than RH
brains, might expect to see less lateral asymmetry in
LH’s brainwaves. If joke comprehension is unrelated
to language lateralization, we might expect similar
ERP effects in both LH and RH subjects.
Participants
32 UCSD Undergrads (16 F)
16 Left-handed (LH) (8 F)
16 Right-handed (RH) (8 F)
Received cash or experimental credit
6 LH participants had a LH immediate family
member (4 F).
Handedness assessed via Edinburgh Inventory
Average Laterality Quotient: LH = -51, RH = 71
Monolingual native English speakers
Normal vision, no history of reading or neurological difficulties
Battery of verbal
ability tests used to
divide participants
into groups of high
and low verbal
ability within each
handedness group
Marianna’s questions:
Familial sinistrality,
Semantic Relations
Test, Laterality
Quotients
Methods
• Each participant read 240 sentences
– 80 jokes (e.g., A replacement player hit a homerun with my girl)
– 80 straights (e.g., “A replacement player hit a homerun with my
ball”)
– 80 expecteds (e.g., “My green car blocked the narrow
driveway”)
– Each participant read 240 sentences
All participants saw the same fillers, but the 160 pairs of
experimental sentences were in 2 different lists, so one group
saw the straight versions of the other group’s jokes and vice
versa.
Published word association norms: joke and straight endings
equally surprising
Sample experimental stimuli
Israel’s questions:
• Excessive muscle activity =
laughter = artifact?
• Variability in sense of
humor – differences in
waveforms?
Procedure
•
•
•
•
•
•
•
•
Electrically shield, sound attenuated chamber
Rapid serial visual presentation (200 ms/word)
Asked to read for comprehension
After each sentence, a comprehension sentence
presented and asked to judge whether (Y/N) consistent
with previous item
Items preceded by fixation cross
Inter-stimulus interval varied as function of worldlength (i.e., 200 ms + 32 ms/character)
Blank screen for 2500 ms between target sentence and
comprehension sentence
Comprehension sentence (4 s), then blank screen (2 s)
before next trial
EEG Recording
• 29 tin electrodes in Electro-Cap
• Referenced to left mastoid
• 10-20 sites: FP1, FPZ, FP2, F7, F3, FZ, F4, F8, FT7, FC3, FCZ, FC4,
FT8, C3, CZ, C4, TP7, CP3, CPZ, CP4, TP8, T5, P3, PZ, P4, T6, O1,
OZ, O2.
• Eye moments monitored via bipolar montage of electrodes
placed at outer canthi
• Blinks monitored via electrode placed on infraorbital ridge of
right eye and referenced to left mastoid
• EEG also recorded at right mastoid, and all data were rereferenced and averaged to the average of the left & right
mastoids.
• Electrode impedances kept below 5kΏ
• EEG processed through SA Instrumentation amplifiefiers set at a
band pass of 0.01-40 Hz, and continuously digitized at 250 Hz.
Data analysis
• Visual inspection, trials rejected when contaminated by
artifacts (excessive eye moments, muscle activity, amplifier
blocking, drift)
• Participants with >40% rejection rates were excluded (4 LH, 3
RH).
• ERPs computed for recording epochs from 100 ms pre-stim
onset baseline to 920 ms post-onset.
• Averages of artificat-free ERP trials calculated for each type
of target word (jokes, straights, expecteds)
• Quantified using mean amplitude of waveforms 300-500,
500-700, and 700-900 ms post onset relative to the baseline.
• RM ANOVA
– Between variables: Handedness, verbal ability, and sex
– Within variables: Ending, hemisphere, and anterior/posterior
scalp site.
– Huhyn-Feldt correction
Percent correct on comprehension questions (standard error)
Trials for which comprehension judgment task incorrectly answered not included
in ERP data analysis.
Israel’s Question
Every time I wear my spring coat in the rain, it
damages the springs.
Comprehension sentence: Water isn’t good
for my coat.
Correct response: YES.
I don't see how they need to understand the
joke in order to answer this question, they
could simply be relying on general world
knowledge (e.g. Rain is not good for coats).
Lynn’s Question
They do not report (or perhaps did not record) the
reaction time it took the participants to answer the
comprehension questions. If they had reported
reaction times to the questions would speed of
processing diffferences been revealed between right
and left handers, or males and females or between
the high and low vocabulary groups? It would be
helpful to see if some kind of behavioral measure
correlated to the ERP results they report
Example may be bad one, but even so, what if comprehension question clarifies
joke to those who didn’t understand initially – difference between initial reaction
and slightly later comprehension
Results
• Sustained negativity 500-900 MS Right Handers (RH)
• ERPs to jokes slightly more negative than to straights on central & parietal endings among
left-handers (C3, C4, P3, P4)
•Left-handers appear more bilaterally symmetrical
• Interaction of ending & anterior-posterior factor:
ERPs to jokes slightly more positive than straights of
prefrontal sites (FP1 and FP2) and more negative than
straights over central & parietal sites. Posterior negativity
thought to reflect the N400.
• N400 best seen low verbal ability, lefthanders P3 & P4 sites.
• Greater bilateral symmetry in left-handers
•Right handers: negative-going ERP effect only
over anterior left lateral sites, distinct from
N400 effect.
Albert’s question:
"Typical of ERPs to visually presented words, all
stimuli elicited N1, P2, and N400."
-Amplitude sensitive to semantic violation?
-Semantic integration
-General wrap up & decision making at end of
sentence
-Not sensitive to negation
• “A robin is a bird” vs. “A robin is a tree”
•“A robin is NOT a bird” vs. “A robin is NOT
a tree”
Late Positivities
• Late positivity broader and
more bilaterally symmetric in LH
females
• Larger corpus callosal areas 
more efficient inter-hemisphere
communication?
•Pawel’s question:
•Inter-hemisphere
communication, or hemisphere
asymmetries?
•Half-field ERP study
• Late positivity in males
Discussion
Negativity: 300 – 500 ms
• Coulson & Kutas (2001): larger amplitude N400 to subset of jokes
Current study
• Only observed in low verbal ability left handers.
• Right handers: negative-going effect only evident only left lateral electrode
sites – distinct from N400.
Absence of strong N400 joke effect:
• Low vs. high constraint jokes
• High: “I asked the hostess if she remembered me from the party last
year, and she said she never forgets a face/dress”
• Low: “My husband took all the money we had been saving to buy a
new car and blew it at the movies/tables”
• 30% joke stimuli  led to a joke “set” that facilitated processing of jokes
that may have reduced N400 effects.
Discussion:
Late Positivity
• Jokes elicited more positive ERPs than straights, but
differed as a function of handedness & sex.
• Left-handed women, expected to have largest corpus
callosal areas, show most laterally symmetric ERPs,
other groups show largest late positivity to jokes over
the right hemisphere.
• Sex confounded by familial sinistrality – 4/8 F had LH
relative; only 2/8 M
• Remote possibility that ERP effects come from skull
thickness, or cranial differences – requires further
examination with electrophysiological & radiological
techniques
Discussion:
Sustained anterior negativity
• Coulson & Kutas (2001): jokes elicited sustained
anterior negativity 500-900 ms over left lateral
electrode sites, argued to index frame-shifting
necessary to get a joke because evident in both
high and low constraint jokes, and absent in ERPs
from poor joke comprehenders.
• Effect found in right handers, but missing from
left-handers despite equivalent comprehension
performance. Instead, waveforms from left and
right anterior sites symmetrical, suggesting
different, bilateral processes in left handers.
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