Unravelling the effects of language sequence and proficiency on intra-sentential multiple code-switching among Chinese-English-Japanese trilinguals: ERP evidence from n-2 language repetition costs

The current study represents the first attempt to investigate n-2 language repetition costs in sentence comprehension, adopting event-related potentials (ERPs) to examine the neural mechanisms underlying intra-sentential multiple code-switching among Chinese-English-Japanese trilinguals. Specifically, the study explores the impact of language sequence (ABA, CBA) and language proficiency (L1, L2, L3) on intra-sentential multiple code-switching processing. The study finds that Chinese-English-Japanese trilinguals experience n-2 language repetition costs when processing intra-sentential multiple code-switching, as evidenced by significant ERP component changes. Furthermore, the results show that differences in neural mechanisms arise based on language sequences, with CBA sequences eliciting larger P200 and ABA sequences producing more negative N400 effects, indicating the influence of language sequence on comprehension. Language proficiency modulated these effects, with L2 and L3 stimuli eliciting larger P200 and Late Positive Component (LPC) amplitudes compared to L1, suggesting that less proficient languages demand higher cognitive load during comprehension. This study provides evidence that n-2 language repetition costs are involved in intra-sentential code-switching processing, with both language sequence and language proficiency modulating the cognitive demands of code-switching.