How does bilingual experience modulate visual processing?

Abstract

Previous bilingual studies showed reduced hemispheric asymmetry in visual tasks such as face perception in bilinguals compared with monolinguals, which suggested that hemispheric asymmetry in visual tasks could be modulated by experience in reading one or two languages. Here I examined whether differences in hemispheric asymmetry in visual tasks can also be observed in bilinguals who have different language backgrounds. I compared the behavior of three language groups: (1) English monolinguals, who acquire only one alphabetic language, (2) European-English bilinguals, who know two alphabetic languages, and (3) Chinese-English bilinguals, who master an alphabetic language and a logographic language; in three tachistoscopic tasks: (1) English word sequential matching task, (2) Intact-altered face judgment task, and (3) face sequential matching task. The results showed that European-English bilinguals had a stronger right visual field (RVF)/ left hemispheric (LH) advantage in the English word sequential matching task than English monolinguals and Chinese-English bilinguals, suggesting that different language learning experiences can influence how visual words are processed in the brain. However, the results showed no group difference between the left visual field (LVF)/ right hemisphere (RH) advantage in the intact-altered face judgment task and the face sequential matching task. These results suggested a modulation of language experience on visual word processing but not on face processing. In addition, I showed that the hemispheric asymmetry in visual word processing could be accounted for by a computational model that implements a theory of hemispheric asymmetry in perception (i.e. the Double Filtering by Frequency theory, Ivry & Robertson, 1998); the modeling data suggested that this lateralization difference in visual word processing may be due to both the difference in participants’ vocabulary size and the difference in word-to-sound mapping between alphabetic and logographic languages.