LLM Reasoning for Machine Translation: Synthetic Data Generation over Thinking Tokens

Fuente: arXiv
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Auteurs principaux: Zebaze, Armel, Bawden, Rachel, Sagot, Benoît
Format: Preprint
Publié: 2025
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author Zebaze, Armel
Bawden, Rachel
Sagot, Benoît
author_facet Zebaze, Armel
Bawden, Rachel
Sagot, Benoît
contents Large reasoning models (LRMs) have led to new possibilities in terms of problem-solving, through the devising of a natural language thought process prior to answering a query. While their capabilities are well known across mathematics and coding tasks, their impact on the task of machine translation (MT) remains underexplored. In this work, we explore the benefits of the generation of intermediate tokens when performing MT across multiple language pairs of different levels of resourcedness and multiple setups. We find that "thinking tokens" do not help LRMs better perform MT. This result generalizes to models fine-tuned to reason before translating using distilled chain of thought (CoT) inspired by human translators' practices. Specifically, fine-tuning a model with synthetic CoT explanations detailing how to translate step-by-step does not outperform standard input-output fine-tuning. However, constructing the intermediate tokens by combining the outputs of modular translation-specific prompting strategies results in improvements. Our findings underscore that the contribution of intermediate tokens during fine-tuning highly depends on the presence of translation attempts within them. More broadly, our results suggest that using a teacher to refine target translations or to expand parallel corpora is more impactful than distilling their CoT explanations into "thinking" MT models.
format Preprint
id arxiv_https___arxiv_org_abs_2510_11919
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle LLM Reasoning for Machine Translation: Synthetic Data Generation over Thinking Tokens
Zebaze, Armel
Bawden, Rachel
Sagot, Benoît
Computation and Language
Large reasoning models (LRMs) have led to new possibilities in terms of problem-solving, through the devising of a natural language thought process prior to answering a query. While their capabilities are well known across mathematics and coding tasks, their impact on the task of machine translation (MT) remains underexplored. In this work, we explore the benefits of the generation of intermediate tokens when performing MT across multiple language pairs of different levels of resourcedness and multiple setups. We find that "thinking tokens" do not help LRMs better perform MT. This result generalizes to models fine-tuned to reason before translating using distilled chain of thought (CoT) inspired by human translators' practices. Specifically, fine-tuning a model with synthetic CoT explanations detailing how to translate step-by-step does not outperform standard input-output fine-tuning. However, constructing the intermediate tokens by combining the outputs of modular translation-specific prompting strategies results in improvements. Our findings underscore that the contribution of intermediate tokens during fine-tuning highly depends on the presence of translation attempts within them. More broadly, our results suggest that using a teacher to refine target translations or to expand parallel corpora is more impactful than distilling their CoT explanations into "thinking" MT models.
title LLM Reasoning for Machine Translation: Synthetic Data Generation over Thinking Tokens
topic Computation and Language
url https://arxiv.org/abs/2510.11919