Cross-lingual transfer, where a high-resource transfer language is used to improve the accuracy of a low-resource task language, is now an invaluable tool for improving performance of natural language processing (NLP) on low-resource languages. However, given a particular task language, it is not clear which language to transfer from, and the standard strategy is to select languages based on ad hoc criteria, usually the intuition of the experimenter. Since a large number of features contribute to the success of cross-lingual transfer (including phylogenetic similarity, typological properties, lexical overlap, or size of available data), even the most enlightened experimenter rarely considers all these factors for the particular task at hand. In this paper, we consider this task of automatically selecting optimal transfer languages as a ranking problem, and build models that consider the aforementioned features to perform this prediction. In experiments on representative NLP tasks, we demonstrate that our model predicts good transfer languages much better than ad hoc baselines considering single features in isolation, and glean insights on what features are most informative for each different NLP tasks, which may inform future ad hoc selection even without use of our method. Code, data, and pre-trained models are available at https://github.com/neulab/langrank

该论文探讨了如何自动选择最佳转移语言作为排名问题，建立模型考虑诸如语言相似性，类型学特性，词汇重叠或可用数据大小等因素以执行这种预测。在代表性NLP任务的实验中，我们证明了我们的模型比单一特征的单独考虑的基准线更好地预测良好的转移语言，并了解了哪些特征对每种不同的NLP任务是最有信息量的，这可能会为未来的专家选择提供帮助。

跨语言学习中的转移语言选择