CoCo-CoLa: Evaluating and Improving Language Adherence in Multilingual LLMs

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Hauptverfasser: Rahmati, Elnaz, Ziabari, Alireza S., Dehghani, Morteza
Format: Preprint
Veröffentlicht: 2025
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author Rahmati, Elnaz
Ziabari, Alireza S.
Dehghani, Morteza
author_facet Rahmati, Elnaz
Ziabari, Alireza S.
Dehghani, Morteza
contents Multilingual Large Language Models (LLMs) develop cross-lingual abilities despite being trained on limited parallel data. However, they often struggle to generate responses in the intended language, favoring high-resource languages such as English. In this work, we introduce CoCo-CoLa (Correct Concept - Correct Language), a novel metric to evaluate language adherence in multilingual LLMs. Using fine-tuning experiments on a closed-book QA task across seven languages, we analyze how training in one language affects others' performance. Our findings reveal that multilingual models share task knowledge across languages but exhibit biases in the selection of output language. We identify language-specific layers, showing that final layers play a crucial role in determining output language. Accordingly, we propose a partial training strategy that selectively fine-tunes key layers, improving language adherence while significantly reducing computational cost. Our method achieves comparable or superior performance to full fine-tuning, particularly for low-resource languages, offering a more efficient multilingual adaptation.
format Preprint
id arxiv_https___arxiv_org_abs_2502_12476
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle CoCo-CoLa: Evaluating and Improving Language Adherence in Multilingual LLMs
Rahmati, Elnaz
Ziabari, Alireza S.
Dehghani, Morteza
Computation and Language
Multilingual Large Language Models (LLMs) develop cross-lingual abilities despite being trained on limited parallel data. However, they often struggle to generate responses in the intended language, favoring high-resource languages such as English. In this work, we introduce CoCo-CoLa (Correct Concept - Correct Language), a novel metric to evaluate language adherence in multilingual LLMs. Using fine-tuning experiments on a closed-book QA task across seven languages, we analyze how training in one language affects others' performance. Our findings reveal that multilingual models share task knowledge across languages but exhibit biases in the selection of output language. We identify language-specific layers, showing that final layers play a crucial role in determining output language. Accordingly, we propose a partial training strategy that selectively fine-tunes key layers, improving language adherence while significantly reducing computational cost. Our method achieves comparable or superior performance to full fine-tuning, particularly for low-resource languages, offering a more efficient multilingual adaptation.
title CoCo-CoLa: Evaluating and Improving Language Adherence in Multilingual LLMs
topic Computation and Language
url https://arxiv.org/abs/2502.12476