Hemisphere lateralization is influenced by bilingual status and composition of words

It has been generally accepted that the left hemisphere is more functionally specialized for language than the right hemisphere for right-handed monolinguals. But more and more studies have also demonstrated right hemisphere advantage for some language tasks with certain participants. A recent comprehensive survey has shown that hemisphere lateralization of language depends on the bilingual status of the participants, with bilateral hemispheric involvement for both languages of early bilinguals, who acquired both languages by age of 6, left hemisphere dominance for language of monolinguals, and also left hemisphere dominance for both languages of late bilinguals, who acquired the second language after age of 6. We propose a preliminary model which takes into account both composition of stimulus words and bilingual status of participants to resolve the apparent controversies regarding hemisphere lateralization of various reading experiments in the literature with focus on Chinese characters, and to predict lateralization patterns for future experiments in Chinese word reading. The bilingual status includes early bilingual, late bilingual and monolingual. However, we have tested this model only with late Chinese-English bilingual participants by using a Stroop paradigm in this paper, though the aim of our model is to disentangle the controversies in the lateralization effect of Chinese character reading. We show here with stimuli written in Chinese single characters that the Stroop effect was stronger when the stimuli were presented to the right than to the left visual field, implying that the language information and color identification/naming may interact more strongly in the left hemisphere. Therefore, our experimental results indicate left hemisphere dominance for Chinese character processing, providing evidence for one part of our model.