Although cross-linguistic influence at the level of morphosyntax is one of the most intensively studied topics in child bilingualism, the circumstances under which it occurs remain unclear. In this meta-analysis, we measured the effect size of cross-linguistic influence and systematically assessed its predictors in 750 simultaneous and early sequential bilingual children in 17 unique language combinations across 26 experimental studies. We found a significant small to moderate average effect size of cross-linguistic influence, indicating that cross-linguistic influence is part and parcel of bilingual development. Language dominance, operationalized as societal language, was a significant predictor of cross-linguistic influence, whereas surface overlap, language domain and age were not. Perhaps an even more important finding was that definitions and operationalisations of cross-linguistic influence and its predictors varied considerably between studies. This could explain the absence of a comprehensive theory in the field. To solve this issue, we argue for a more uniform method of studying cross-linguistic influence.

尽管形态句法层面的跨语言影响是儿童双语中研究最深入的主题之一，但其发生的环境仍不清楚。在这项荟萃分析中，我们测量了跨语言影响的影响大小，并系统地评估了 26 项实验研究中 17 种独特语言组合中 750 名同时和早期连续双语儿童的预测因子。我们发现跨语言影响的平均效应大小显着小到中等，表明跨语言影响是双语发展的重要组成部分。作为社会语言运作的语言优势是跨语言影响的重要预测因素，而表面重叠、语言领域和年龄则不是。也许更重要的发现是跨语言影响的定义和操作及其预测因子在研究之间存在很大差异。这可以解释该领域缺乏综合理论的原因。为了解决这个问题，我们主张采用更统一的方法来研究跨语言影响。