Abstract The experience of speaking two languages, particularly the age of second language acquisition (L2AoA), has been robustly associated with differences in metrics indicative of white matter structure. However, bilingual language experience is complex, described not only by acquisition but also functional language usage and proficiency. We examined whether the onset age of the second most proficient language (pL2AoA) would indeed be a sensitive measure that incorporates onset age of second language acquisition and self-reported L2 proficiency and correlates with variation in fractional anisotropy in white matter. Thirty-one multilingual young adults with a range of L2AoA and pL2AoA from an English-dominant community participated. After accounting for age, gender, nonverbal IQ, and parental education, both L2AoA and pL2AoA were significantly correlated with fractional anisotropy in the corpus callosum. Furthermore, we show that a larger and more extensive cluster in the corpus callosum was correlated with pL2AoA as compared to the conventional L2AoA.

中文翻译：

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多语种年轻人第二语言习得的开始年龄和各向异性分数变异

摘要 说两种语言的经历，尤其是第二语言习得年龄 (L2AoA)，与指示白质结构的指标差异密切相关。然而，双语语言体验是复杂的，不仅可以通过习得来描述，还可以通过功能性语言使用和熟练程度来描述。我们检查了第二熟练语言 (pL2AoA) 的开始年龄是否确实是一个敏感的衡量标准，它结合了第二语言习得的开始年龄和自我报告的 L2 熟练程度，并与白质各向异性分数的变化相关联。来自以英语为主导的社区的 31 名具有多种 L2AoA 和 pL2AoA 的多语种年轻人参加了此次会议。在考虑了年龄、性别、非语言智商和父母教育后，L2AoA 和 pL2AoA 均与胼胝体的各向异性分数显着相关。此外，我们表明，与传统的 L2AoA 相比，胼胝体中更大、更广泛的集群与 pL2AoA 相关。