CAR-Transformer: Cross-Attention Reinforcement Transformer for Cross-Lingual Summarization

Cross-Lingual Summarization (CLS) involves generating a summary for a given document in another language. Most of the existing approaches adopt multi-task training and knowledge distillation, which increases the training cost and improves the performance of CLS tasks intuitively but unexplainably. In this work, we propose Cross-Attention Reinforcement (CAR) module and incorporate the module into the transformer backbone to formulate the CAR-Transformer. The CAR module formulates a pseudo summarization policy parameterized by the cross-attention weights reinforced by the ground-truth monolingual summary without introducing extra model parameters. Our approach demonstrates more consistent improvement across CLS tasks compared to traditional multi-task training methods and outperforms the fine-tuned vanilla mBART by 3.67 and the best-performing multi-task training approach by 1.48 in ROUGE-L F1 score on the WikiLingua Korean-to-English CLS task.