中英雙語兒童構詞覺識的大腦基礎

Abstract

本研究旨在探討雙語學習對兒童閱讀發展之神經結構的影響，並透過研究雙語兒童的構詞覺識來探索此研究問題。由於中、英文在構詞結構上的差異，構詞處理的神經機制將可以反映跨語言遷移對兒童識字能力發展的影響。為了研究跨語言差異對雙語兒童發展的影響，本研究招募了 39 名中文單語和 53 名中英雙語小學一年級的兒童，並請他們進行聽覺構詞判斷作業，同時利用功能性近紅外光譜（fNIRS）量測其大腦皮質活動。在聽覺構詞判斷作業中，兒童依序聽到三個單詞，並決定後兩個詞中何者與首詞具有相同的構詞詞根或派生詞綴。所有中文刺激皆包含兩個中文字，其中一個字在三個單詞中皆具有相同的發音，而所有英文刺激皆為單個英文單字。單語兒童進行中文聽覺構詞判斷作業，雙語兒童則進行中文和英文聽覺構詞判斷作業。功能性近紅外光譜結果顯示雙語兒童在處理英文和中文構詞時出現不同的神經表徵，展現出語言獨特性效果。此外，相較於中文作業，雙語兒童在英文作業中出現了更強的右腦半球活化，顯示出雙語兒童需要額外的認知資源來協助處理他們的第二語言。更重要的是，本研究結果支持了跨語言遷移效果。相較於中文單語兒童，中英雙語兒童在中文作業中出現了較強的左側後顳上迴/顳中迴活化。此外，具有較高英文讀寫能力的雙語兒童展現了更強的左側後顳上迴/顳中迴活化。這些研究結果顯示，雙語兒童能夠遷移英文的字詞切割和結構分析能力來協助中文的構詞處理。綜合上述研究結果，本研究發現了雙語兒童能夠活化不同的神經網路來處理個別語言，從小同時接觸具不同構詞結構特性的語言，將能夠影響雙語兒童的早期識字能力發展。

This study aims to investigate the influence of bilingualism on children’s neural architecture of reading development. We explore this inquiry by focusing on bilingual children’s morphological awareness. Due to the structural differences in morphology between Chinese and English, the neural substrates of morphological processing could reflect the cross-linguistic transfer effects on children’s literacy development. To examine the influence of cross-linguistic differences on bilingual children’s development, we recruited 39 Chinese monolingual and 53 Chinese-English bilingual first graders to complete an auditory morphological judgment task during the functional Near Infracted Spectroscopy (fNIRS) neuroimaging. During the task, participants heard three spoken words sequentially and were instructed to choose the word (i.e., answer) that shared a morphemic root or derivational affix with the first word (i.e., target), as compared to the phonologically similar word (i.e., distractor). All Chinese stimuli involved two characters, one of which had the same sound across the target, answer, and distractor words, while all English stimuli were single English words. Monolingual participants completed the task in Chinese, and bilingual participants completed the task in both Chinese and English. fNIRS results revealed the language-specific effect, with bilingual children showing different neural representations when processing English and Chinese morphology. Additionally, bilingual children elicited stronger activation over the right hemisphere in the English relative to the Chinese task, suggesting the necessity of additional cognitive resources to process their second language. Critically, the results demonstrated the cross-linguistic transfer effect. Compared to monolinguals, bilingual children showed stronger activation over the left posterior superior/middle temporal gyrus in the Chinese task. Moreover, bilingual children with higher English literacy ability displayed increased engagement in the left posterior superior/middle temporal gyrus. These findings suggest that bilingual children transfer word segmentation and structural analysis in English to support Chinese morphology processing. Collectively, this study indicates that bilingual children employ different neural circuities for processing each language and that exposure to a language with a different structure influences children’s processing strategies for early literacy development.