It is well established that L2 acquisition is faster when the L2 is more closely related to the learner’s L1. In the current study we investigated whether language similarity has a comparable facilitative effect in early simultaneous bilingual children. The similarity between each bilingual child’s two languages was determined using phonological and typological scales. We compared the vocabulary size of bilingual toddlers learning different pairs of languages. Results show that the vocabulary size of bilingual children is indeed influenced by similarity: the more similar the languages, the larger the children’s vocabulary.

中文翻译：

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语言相似性是否影响早期同时双语习得？

众所周知，当 L2 与学习者的 L1 更密切相关时，L2 习得更快。在目前的研究中，我们调查了语言相似性是否对早期同时使用双语的儿童具有类似的促进作用。每个双语儿童的两种语言之间的相似性是使用语音和类型量表来确定的。我们比较了学习不同语言对的双语幼儿的词汇量。结果表明，双语儿童的词汇量确实受到相似性的影响：语言越相似，儿童的词汇量就越大。