The Effects of Onset-Age and Exposure Duration on the L2 as Observed in Brain Activation: an fNIRS Study

This study aims to examine how the age of exposure to L2 English (onset-age or OA) and exposure duration (length of residence or LOR) affect brain activation using the fNIRS machine. Thirty-two Japanese-English bilinguals were divided into four groups according to the level of English proficiency based on their OA and LOR. While wearing the brain cap to monitor brain waves, the participants were individually presented with two tasks a verbal fluency task and a numeral task in two languages, English and Japanese. Behavioural data showed no significant differences among four groups, which proved the task difficulty was equal among the groups. The results firstly demonstrated that the earlier one's initial intensive and extensive exposure to an L2 is, the less the brain activation in both hemispheres is observed, even in those who were exposed to their L2 before the critical period. The second finding revealed that brain activation decreases in both hemispheres as one's L2 proficiency improves. ∗ Professor, Graduate School of Language Education and Information Science ∗∗ Graduate students, Graduate School of Language Education and Information Science TAURA, Hideyuki and NASU, Aoi 20