Hemispheric differences in grammatical class: A hemifield investigation

Although a number of studies have examined lexical asymmetries in hemispheric processing, few have systematically investigated differences between nouns and verbs. Lateralization effects of grammatical class were examined by presenting nouns and verbs of both high and low frequencies to either the right or left visual field. Results from a noun/verb categorization task revealed a significant visual field by grammatical class interaction: Verbs were processed faster in the left compared to the right hemisphere, while there was no hemispheric advantage for the processing of nouns.

The present study provides new evidence for the role of grammatical class in lexical processing. These behavioral results, in combination with imaging data from fMRI (Pugh et aI., 1997), suggest that lexical knowledge is organized so that representations of different grammatical categories are processed by different brain mechanisms.