Morphological structure and hemispheric functioning: the contribution of the right hemisphere to reading in different languages.

This study examined the relationship between morphological structure of languages and performance asymmetries of native speakers in lateralized tasks. In 2 experiments, native speakers of English (concatenative morphology stem plus affix) and of Hebrew and Arabic (nonconcatenative root plus word-form morphology) were presented with lateralized lexical decision tasks, in which the morphological structure of both words and nonwords was manipulated. In the 1st study, stimuli were presented unilaterally. In the 2nd study, 2 stimuli were presented bilaterally, and participants were cued to respond to 1 of them. Three different indexes of hemispheric integration were tested: processing dissociation, effects of distractor status, and the bilateral effect. Lateralization patterns in the 3 languages revealed both common and language-specific patterns. For English speakers, only the left hemisphere (LH) was sensitive to morphological structure, consistent with the hypothesis that the LH processes right visual field stimuli independently but that the right hemisphere uses LH abilities to process words in the left visual field. In Hebrew and Arabic, both hemispheres are sensitive to morphological structure, and interhemispheric transfer of information may be more symmetrical than in English. The relationship between universal and experience-specific effects on brain organization is discussed.