Do bilinguals have a different hemispheric lateralization in visual processing from monolinguals?

Abstract

Previous studies showed reduced hemispheric asymmetry in non-verbal tasks such as face perception for alphabetic bilinguals compared to alphabetic monolinguals (Hausmann et al., 2004). Nevertheless, it remains unclear whether this effect can also be observed in bilinguals of a logographic language (such as Chinese) and an alphabetic language. Since logographic language and alphabetic languages are dramatically different in their orthography and how orthographic components are mapped to pronunciations and meanings, bilinguals of a logographic and an alphabetic language may have different visual experience than bilinguals and monolinguals of alphabetic languages. In this study, we aimed to examine whether reduced hemispheric asymmetry in non-verbal tasks can also be observed in Chinese-English bilinguals. We compared results of Chinese-English bilinguals and English monolinguals in three tachistoscopic identification tasks: Chinese character sequential matching task, English word sequential matching task, and intact-altered face recognition task. In the reaction time data, we found faster response times for both Chinese character and English word targets presented in the right visual field than in the left visual field (i.e. left hemisphere advantage) in bilingual participants; in contrast, faster response times in the right visual field were only observed for English word targets in monolingual participants. In the discrimination sensitivity measures (D-prime), we found that both monolinguals and bilinguals exhibited a left visual field/right hemisphere advantage for Chinese character matching and a right visual field/left hemisphere advantage for English word matching; in addition, there was more lateralization for bilinguals than monolinguals. In contrast to the results of Hausmann et al. (2004), we failed to observe a difference in lateralization in the intact-altered face recognition task between English monolinguals and Chinese-English bilinguals. Our results suggest that different kinds of language experience may have different influences on hemispheric lateralization in visual processing.