This paper describes our system developed for the SemEval-2023 Task 12 "Sentiment Analysis for Low-resource African Languages using Twitter Dataset". Sentiment analysis is one of the most widely studied applications in natural language processing. However, most prior work still focuses on a small number of high-resource languages. Building reliable sentiment analysis systems for low-resource languages remains challenging, due to the limited training data in this task. In this work, we propose to leverage language-adaptive and task-adaptive pretraining on African texts and study transfer learning with source language selection on top of an African language-centric pretrained language model. Our key findings are: (1) Adapting the pretrained model to the target language and task using a small yet relevant corpus improves performance remarkably by more than 10 F1 score points. (2) Selecting source languages with positive transfer gains during training can avoid harmful interference from dissimilar languages, leading to better results in multilingual and cross-lingual settings. In the shared task, our system wins 8 out of 15 tracks and, in particular, performs best in the multilingual evaluation.

通过利用语言自适应和任务自适应的预训练模型，本文针对非洲语言低资源性情感分析问题的特点，研究了基于预训练的语言模型的迁移学习方法，并发现将预训练模型适应到目标语言和任务上可以显著提高模型表现，选择具有积极转移增益的源语言可以避免干扰，这在多语言和跨语言设置中可以取得更好的结果。

NLNDE at SemEval-2023 Task 12: 低资源多语言情感分析的自适应预训练和源语言选择