Hemispheric asymmetries and joke comprehension Coulson, S., & Williams, R. F. (2005) Neuropsychologia, 43,

Background Joke comprehension seems to include 2 parts: surprise and updating (frame-shifting) “I asked the bartender for something cold and full of rum, and he recommended …” a daiquiri = expected; fits context of bar and drinks his wife = unexpected; requires reevaluation of sentence context (cold + rum = bartender’s wife)

ERPS & Joke Comprehenison Coulson & Kutas, 2000 Are there 2 separate stages? Recorded ERPs while participants read RSVP sentences that ended with either a joke or non-joke word (wife/daiquiri) Why ERPs?  temporally precise: can examine timecourse of joke comprehension, specifically when surprise and updating stages occur, or if they are even separate

ERPS & Joke Comprehenison Coulson & Kutas, 2000 Stimuli  Jokes and non-joke controls were identical until final word  Joke and non-joke endings were matched on cloze probability (~3%)  They were further divided by the constraint of the sentence, or cloze probability of the most popular response High constraint (> 40% cloze prob.) “She read so much about the bad effects of smoking that she decided she’d have to give up reading/the habit.” Low constraint (< 40% cloze. Prob.) “Statistics indicate that Americans spend 80 million a year on games of chance, mostly weddings/dice.”

ERPS & Joke Comprehenison Coulson & Kutas, 2000 Procedure  200ms per word; 500ms for last word  Sentence followed with true/false comprehension question, to ensure correct interpretation of joke e.g., “The bartender suggested a frozen drink” “The bartender’s wife was a frigid lush” Responses were used to divide good comprehenders (avg. 83% correct) and bad comprehenders (avg. 64% correct) All but one subject scored above 83% on non-jokes, so comprehension problems were only with jokes

ERPS & Joke Comprehenison Coulson & Kutas, 2000 Enhanced N400 for joke endings  Negative-going wave, peaking ~400ms  Distribution: broad, slightly right- lateralized, stronger over centro- parietal areas  Enhanced N400s typically associated with difficulty of lexical processing/ integration LAN (left anterior negativity / sustained negativity)  Associated with WM demands and updating sentences

ERPS & Joke Comprehenison Coulson & Kutas, 2000 Effects varied with comprehension and constraint groupings N400  Broader N400 distribution for poor comprehenders (distribution for good comprehenders more canonical)  N400 effects only significant for high constraint sentences LAN  Only present for good comprehenders, regardless of constraint

ERPS & Joke Comprehenison Coulson & Kutas, 2000 Conclusions Joke endings produced an N400 effect only in constraining sentence contexts  This seems to represent the surprise element of the joke ending  But the distribution varied, and the effect was stronger for poor comprehenders Good comprehenders also showed a LAN  Seems to represent updating the sentence context However, authors conclude that these 2 components do not support the 2-stage theory, because of temporal overlap

Evidence for hemispheric asymmetries? Studies on unilateral brain damage have shown different deficits in joke comprehension  LHD (left hemisphere brain damage) => problems with recognizing the initial disruption  RHD (right hemisphere brain damage) => problems with updating the sentence context appropriately Neuroimaging studies (fMRI) have shown increased activation in the RH (right hemisphere) during joke comprehension

Visual Half-field Paradigm Stimuli presented in one hemifield are received by contralateral hemisphere RVF (right visual field)  LH (left hemisphere) LVF (left visual field)  RH (right hemisphere) Subjects fixate centrally; stimuli are then presented to the left (left visual field: LVF) or to the right (right visual field: RVF) of fixation

Coulson & Williams, 2005: Design Stimuli  Same as 2000 study, but now sentence-final joke word is presented to left or right of fixation  Also included expected filler items for comparison Procedure  Read sentence word-by-word  When prompted, name final word (only correctly named words were included in analysis)  Answer comprehension question (>90%)

Coulson & Williams, 2005: Results Predictability effects  Enhanced N400s for joke and non-joke endings, relative to fillers Joke effects  For rvf/LH presentation, larger N400 for jokes than non-jokes  For lvf/RH presentation, no N400 differences

Coulson & Williams, 2005: Results Jokes elicited a LAN – both VFs  Only present at one channel (F7) Jokes elicited frontal positivity – both VFs

Coulson & Williams, 2005: Conclusions Clear differences in how each hemisphere processes jokes  LH showed N400 differences, reflecting difficulty integrating joke ending  RH showed no difference, suggesting that it has no problem understanding jokes Consistent with:  Coarse-coding RH activates a broader array of semantic associates – more prepared for deviation from expected LH has more fine-grained activation – more disrupted by deviation  Prediction / integration RH builds a flexible context – able to accept unexpected items if they still make sense LH rapidly builds context and tries to predict upcoming items – thrown off by contrasting items

DISCUSSION Why are they not getting P600 effects?  Process of joke comprehension seems similar to garden-path processing – why are there differences If N400 effect reflects recognition that the joke is inconsistent with current interpretation, why does it not show up for the RH at all?  If the LAN represents reevaluation, this must have been signaled by inconsistency

DISCUSSION Given that level of constraint and comprehenders’ status was so important in previous study, why not divide into these groups again?