Lexical class and explicitness as neural modulators of metaphor comprehension
Dr. Gwenda Schmidt, Hope College
Inconsistent results due to poorly controlled stimulus sets have pervaded research on the neural basis of metaphor. Previous studies have not often considered the part of speech of the metaphorical word or the explicitness of the metaphorical phrase. Most previous work has focused on metaphors that are nominal (use a noun metaphorically) and explicit (state a clear metaphorical comparison that is directly mapped). Because nouns and verbs possess different neural bases, it may be that nominal and predicate metaphors also have different neural substrates. Research has begun to explore predicate metaphors (where verbs are used in a metaphorical sense) which by nature are implicit (a metaphorical comparison that is indirect or implied). A highly controlled stimulus set was used in an event related potential (ERP) study. ERPs are derived from electroencephalographic (EEG) data collected at the scalp. Stimuli were nominal explicit metaphors (The unexpected divorce was an earthquake) nominal implicit metaphors (The relationship could not withstand the earthquake) or implicit predicate metaphors (Over the canvas the paint danced). Literal sentences (There was chaos in the city after the earthquake) and anomalous sentences (He sloppily taped the picture to the earthquake) served as controls. Brain activity was recorded from 64 electrodes on the scalp of right-handed native English speakers (n=18). Participants decided whether each randomly ordered sentence was literal, anomalous or metaphor. Metaphors elicited a larger N400 (an ERP index of semantic processing difficulty) than literal sentences for both predicate and nominal conditions The difference in N400 between literal and metaphor supports unique neural mechanisms of figurativeness which is not modulated by part of speech. For nominal sentences, the scalp distribution of the N400 was marginally different for implicit and explicit sentences. It is possible that the explicitness of the metaphorical comparison modulates neural processing.
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