Semantic Pivots Enable Cross-Lingual Transfer in Large Language Models

Large language models (LLMs) demonstrate remarkable ability in cross-lingual tasks. Understanding how LLMs acquire this ability is crucial for their interpretability. To quantify the cross-lingual ability of LLMs accurately, we propose a Word-Level Cross-Lingual Translation Task. To find how LLMs learn cross-lingual ability, we trace the outputs of LLMs' intermediate layers in the word translation task. We identify and distinguish two distinct behaviors in the forward pass of LLMs: co-occurrence behavior and semantic pivot behavior. We attribute LLMs' two distinct behaviors to the co-occurrence frequency of words and find the semantic pivot from the pre-training dataset. Finally, to apply our findings to improve the cross-lingual ability of LLMs, we reconstruct a semantic pivot-aware pre-training dataset using documents with a high proportion of semantic pivots. Our experiments validate the effectiveness of our approach in enhancing cross-lingual ability. Our research contributes insights into the interpretability of LLMs and offers a method for improving LLMs' cross-lingual ability.

@article{he2025_2505.16385,
  title={ Semantic Pivots Enable Cross-Lingual Transfer in Large Language Models },
  author={ Kaiyu He and Tong Zhou and Yubo Chen and Delai Qiu and Shengping Liu and Kang Liu and Jun Zhao },
  journal={arXiv preprint arXiv:2505.16385},
  year={ 2025 }
}