Do LLMs Need to Think in One Language? Correlation between Latent Language and Task Performance

Fuente: arXiv
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Autori principali: Ozaki, Shintaro, Hiraoka, Tatsuya, Otake, Hiroto, Ouchi, Hiroki, Isonuma, Masaru, Heinzerling, Benjamin, Inui, Kentaro, Watanabe, Taro, Miyao, Yusuke, Oseki, Yohei, Takagi, Yu
Natura: Preprint
Pubblicazione: 2025
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author Ozaki, Shintaro
Hiraoka, Tatsuya
Otake, Hiroto
Ouchi, Hiroki
Isonuma, Masaru
Heinzerling, Benjamin
Inui, Kentaro
Watanabe, Taro
Miyao, Yusuke
Oseki, Yohei
Takagi, Yu
author_facet Ozaki, Shintaro
Hiraoka, Tatsuya
Otake, Hiroto
Ouchi, Hiroki
Isonuma, Masaru
Heinzerling, Benjamin
Inui, Kentaro
Watanabe, Taro
Miyao, Yusuke
Oseki, Yohei
Takagi, Yu
contents Large Language Models (LLMs) are known to process information using a proficient internal language consistently, referred to as latent language, which may differ from the input or output languages. However, how the discrepancy between the latent language and the input and output language affects downstream task performance remains largely unexplored. While many studies research the latent language of LLMs, few address its importance in influencing task performance. In our study, we hypothesize that thinking in latent language consistently enhances downstream task performance. To validate this, our work varies the input prompt languages across multiple downstream tasks and analyzes the correlation between consistency in latent language and task performance. We create datasets consisting of questions from diverse domains such as translation and geo-culture, which are influenced by the choice of latent language. Experimental results across multiple LLMs on translation and geo-culture tasks, which are sensitive to the choice of language, indicate that maintaining consistency in latent language is not always necessary for optimal downstream task performance. This is because these models adapt their internal representations near the final layers to match the target language, reducing the impact of consistency on overall performance.
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id arxiv_https___arxiv_org_abs_2505_21458
institution arXiv
publishDate 2025
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spellingShingle Do LLMs Need to Think in One Language? Correlation between Latent Language and Task Performance
Ozaki, Shintaro
Hiraoka, Tatsuya
Otake, Hiroto
Ouchi, Hiroki
Isonuma, Masaru
Heinzerling, Benjamin
Inui, Kentaro
Watanabe, Taro
Miyao, Yusuke
Oseki, Yohei
Takagi, Yu
Computation and Language
Large Language Models (LLMs) are known to process information using a proficient internal language consistently, referred to as latent language, which may differ from the input or output languages. However, how the discrepancy between the latent language and the input and output language affects downstream task performance remains largely unexplored. While many studies research the latent language of LLMs, few address its importance in influencing task performance. In our study, we hypothesize that thinking in latent language consistently enhances downstream task performance. To validate this, our work varies the input prompt languages across multiple downstream tasks and analyzes the correlation between consistency in latent language and task performance. We create datasets consisting of questions from diverse domains such as translation and geo-culture, which are influenced by the choice of latent language. Experimental results across multiple LLMs on translation and geo-culture tasks, which are sensitive to the choice of language, indicate that maintaining consistency in latent language is not always necessary for optimal downstream task performance. This is because these models adapt their internal representations near the final layers to match the target language, reducing the impact of consistency on overall performance.
title Do LLMs Need to Think in One Language? Correlation between Latent Language and Task Performance
topic Computation and Language
url https://arxiv.org/abs/2505.21458