Does Masked Language Model Pre-training with Artificial Data Improve Low-resource Neural Machine Translation?

Pre-training masked language models (MLMs) with artificial data has been proven beneficial for several natural language processing tasks such as natural language understanding and summarization; however, it has been less explored for neural machine translation (NMT). A previous study revealed the benefit of transfer learning for NMT in a limited setup, which differs from MLM. In this study, we prepared two kinds of artificial data and compared the translation performance of NMT when pre-trained with MLM. In addition to the random sequences, we created artificial data mimicking token frequency information from the real world. Our results showed that pre-training the models with artificial data by MLM improves translation performance in low-resource situations. Additionally, we found that pre-training on artificial data created considering token frequency information facilitates improved performance.