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arXiv 2601.20009cs.CLcs.AIcs.LG
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LinguaMap:哪些LLM层说你的语言以及如何调节它们?

LinguaMap: Which Layers of LLMs Speak Your Language and How to Tune Them?

Georgia Institute of Technology(佐治亚理工学院);Amazon(亚马逊)

J. Ben Tamo, Daniel Carlander-Reuterfelt, Jonathan Rubin, Dezhi Hong, Mingxian Wang, Oleg Poliannikov

AI总结:

本文提出LinguaMap方法,通过分析LLM各层的语言控制机制,发现语言一致性瓶颈并提出选择性微调策略,实现多语言适应的高效优化。

摘要:

尽管多语言预训练,大型语言模型在非英语任务中往往在语言控制上表现不佳,特别是在能够以预期语言响应的能力上。我们识别并表征了两种关键失败模式:多语言转移瓶颈(正确语言,错误任务响应)和语言一致性瓶颈(正确任务响应,错误语言)。为了系统地揭示这些问题,我们设计了一个涵盖MMLU、MGSM和XQuAD基准的四场景评估协议。为了用可解释性来探测这些问题,我们扩展了logit lens分析,以逐层跟踪语言概率并计算隐藏状态的跨语言语义相似性。结果揭示了内部的三个阶段结构:早期层将输入对齐到共享的语义空间,中间层执行任务推理,晚期层驱动语言特定的生成。受这些见解的启发,我们引入了仅微调负责语言控制的最终层的有选择性微调。在Qwen-3-32B和Bloom-7.1B上,该方法在六种语言中实现了超过98%的语言一致性,仅微调3-5%的参数,而不牺牲任务准确性。重要的是,这一结果几乎与全范围微调的结果相同(例如,在所有提示场景中,两种方法的98%以上语言一致性),但使用了极少的计算资源。到目前为止,这可能是第一个利用语言控制的层局部化来实现高效多语言适应的方法。

英文摘要:

Despite multilingual pretraining, large language models often struggle with non-English tasks, particularly in language control, the ability to respond in the intended language. We identify and characterize two key failure modes: the multilingual transfer bottleneck (correct language, incorrect task response) and the language consistency bottleneck (correct task response, wrong language). To systematically surface these issues, we design a four-scenario evaluation protocol spanning MMLU, MGSM, and XQuAD benchmarks. To probe these issues with interpretability, we extend logit lens analysis to track language probabilities layer by layer and compute cross-lingual semantic similarity of hidden states. The results reveal a three-phase internal structure: early layers align inputs into a shared semantic space, middle layers perform task reasoning, and late layers drive language-specific generation. Guided by these insights, we introduce selective fine-tuning of only the final layers responsible for language control. On Qwen-3-32B and Bloom-7.1B, this method achieves over 98 percent language consistency across six languages while fine-tuning only 3-5 percent of parameters, without sacrificing task accuracy. Importantly, this result is nearly identical to that of full-scope fine-tuning (for example, above 98 percent language consistency for both methods across all prompt scenarios) but uses a fraction of the computational resources. To the best of our knowledge, this is the first approach to leverage layer-localization of language control for efficient multilingual adaptation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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