Late second language (L2) learners report difficulties in specific linguistic areas such as syntactic processing, presumably because brain plasticity declines with age (following the critical period hypothesis). While there is also evidence that L2 learners can achieve native-like online-processing with sufficient proficiency (following the convergence hypothesis), considering multiple mediating factors and their impact on language processing has proven challenging. We recorded EEG while native (n = 36) and L2-speakers of French (n = 40) read sentences that were either well-formed or contained a syntactic-category error. a lexical-semantic anomaly, or both. Consistent with the critical period hypothesis, group differences revealed that while native speakers elicited a biphasic N400-P600 in response to ungrammatical sentences, L2 learners as a group only elicited an N400. However, individual data modeling using a Random Forests approach revealed that language exposure and proficiency are the most reliable predictors in explaining ERP responses, with N400 and P600 effects becoming larger as exposure to French as well as proficiency increased, as predicted by the convergence hypothesis.

中文翻译：

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不断增长的随机森林表明，暴露和熟练程度最能解释 L2（和 L1）大脑语法和语义潜力的个体差异

后期第二语言 (L2) 学习者报告特定语言领域的困难，例如句法处理，大概是因为大脑可塑性随着年龄的增长而下降（遵循关键期假设）。虽然也有证据表明 L2 学习者可以以足够的熟练程度（遵循收敛假设）​​实现类似母语的在线处理，但考虑到多种中介因素及其对语言处理的影响已被证明具有挑战性。我们记录了 EEG，而母语 (n = 36) 和法语 L2 使用者 (n = 40) 阅读的句子要么格式正确，要么包含句法类别错误。词汇语义异常，或两者兼而有之。与关键时期假设一致，群体差异表明，虽然母语者在回应不合语法的句子时会引出双相 N400-P600，L2 学习者作为一个群体只引出了 N400。然而，使用随机森林方法的个人数据建模表明，语言接触和熟练程度是解释 ERP 反应的最可靠预测因素，随着接触法语和熟练程度的增加，N400 和 P600 的影响变得更大，正如收敛假设所预测的那样。