Cross-linguistic influences of L1 on L2 morphosyntactic processing: An fNIRS study

This study examined how the morphological typology of second language (L2) learners' first language (L1) affected neural processing of L2 morphosyntactic knowledge. We used functional near infrared spectroscopy (fNIRS) to examine adult L2 learners' processing of English SubjectVerb number agreement (e.g., duck swims, ducks swim) during a picture-sentence matching task. Two English learner groups with contrasting L1s, Spanish (with rich inflectional morphology, n = 16) and Mandarin (with a lexical morphology, n = 18), were compared to native English speakers (n = 19). Both L2-learner groups demonstrated comparable accuracy on the picture-sentence matching task. However, neural results revealed L1 influence on L2 morphosyntactic processing. Mandarin-speaking English L2 learners showed greater neural activity in the left middle temporal gyrus (L-MTG) for singular (e.g., the duck swims) versus plural sentences (e. g., the ducks swim). Mandarin relies on semantic, rather than inflectional, information to infer number and L-MTG is involved in lexical-semantic processing, suggesting L1 influence on L2 inflectional processing. Spanish-speaking English L2 learners showed greater neural activity in areas including the right MTG and prefrontal cortex for the plural versus singular sentences whereas native English speakers showed greater activity for singular versus plural sentences. The plural form is morphologically marked in Spanish and greater neural activation for the plural rather than singular form suggests L1 influence. Importantly, cross-linguistic influences were only observed at the neural level, revealing that different neural activation patterns underpin similar behavioral results. Both L2-learner groups showed different patterns of neural activation corresponding to the specific linguistic features of their L1, indicating that L2 processing is affected by L1 characteristics in linguistically principled ways. This study advances our understanding of how morphosyntactically-distinct languages are organized and processed in adult L2 learners.