Parent report data on 82 preschool children with complex neurodevelopmental disabilities including Down syndrome, dyspraxia, autism, and global developmental delay suggests communicative language use must reach a threshold level before vocabulary size becomes the best predictor of word combining. Using the Language Use Inventory and the MacArthur-Bates CDI (with sign vocabulary option), statistical modelling using regression trees and random forests suggests that, despite high linear correlations between variables, (1) pragmatic ability, particularly children's emerging ability to talk about things, themselves and others is a significantly better predictor of the earliest word combining than vocabulary size; and (2) vocabulary size becomes a better predictor of later word combining, once this pragmatic base has been established.

中文翻译：

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语言使用和词汇量在复杂神经发育障碍儿童单词组合出现中的作用

家长报告的 82 名患有复杂神经发育障碍（包括唐氏综合症、运动障碍、自闭症和全球发育迟缓）的学龄前儿童的数据表明，在词汇量成为单词组合的最佳预测指标之前，交际语言的使用必须达到阈值水平。使用语言使用量表和 MacArthur-Bates CDI（带有符号词汇选项），使用回归树和随机森林的统计建模表明，尽管变量之间存在高度线性相关性，（1）语用能力，特别是儿童谈论事物的新兴能力，他们自己和其他人比词汇量更能预测最早的单词组合；(2) 一旦建立了这个语用基础，词汇量就可以更好地预测以后的单词组合。