Connecting the Dots: Finding a Unified Theory of Laterality and Modality in Metaphor Comprehension

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Dr. Gwenda Schmidt, Hope College

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Previous research in the neural processing of language has demonstrated that both the right and left hemispheres are involved in the processing of figurative language such as metaphors, idioms, and even humor. Specifically, it has been suggested that the left hemisphere plays a vital role in the processing of literal or more concrete language, while the right hemisphere specializes in processing and integration of language with multiple meanings. However, little research has been conducted investigating how motion and auditory-based figurative language is processed in each hemisphere. Our study was intended to eliminate confounds evident in previous research by controlling for familiarity, naturalness, and imageability of the stimuli presented. A computer program was used to display sentences to participants to either the left or right visual field. Event-related potentials (ERPs) were measured using an EEG system. The N400, our dependant measure, is a negative waveform component of the ERP, which occurs approximately 400 milliseconds post-stimulus and indexes semantic processing difficulty. Stimuli were divided into literal, metaphoric, and anomalous sentences. In addition, the stimuli were equally divided between auditory and motion modalities. Our results confirmed our hypothesis that there would be greater N400 amplitudes for anomalous and metaphorical sentences. In addition to the N400 differences between conditions, we also found a right hemisphere bias when metaphorical sentences were presented, confirming our hypothesis that there would be an interaction effect between visual field and figurativeness. Further assessment of specific scalp locations showed decreased activation in the parietal region when auditory metaphor sentences were presented to the left hemisphere specifically. This suggests there is a significant modality component to figurative language processing. These results are in accordance with existing theories of right hemisphere language involvement, suggesting there is a hemispheric bias when processing literal and metaphoric language, though not as definitive as previously thought.

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