Do Multilingual Language Models Think Better in English?
Julen Etxaniz, Gorka Azkune, Aitor Soroa, Oier Lopez de Lacalle, Mikel Artetxe
TL;DR
This work probes whether translate-test improvements for multilingual language models arise from external translation resources or from the models' inherent multilingual capabilities. It introduces self-translate, a prompting-based approach that uses the model to translate inputs into English before solving tasks in English, thereby removing the need for an external MT system. Across five tasks and multiple model families, self-translate consistently outperforms direct non-English prompting, with larger gains for high-resource languages and bigger models; while external MT can still beat self-translate, the gap narrows as model scale increases. The study highlights a fundamental limitation in exploiting multilingual potential through prompting alone and suggests that scaling and instruction-tuning may further reduce reliance on intermediate translation steps, enhancing practical multilingual reasoning capabilities.
Abstract
Translate-test is a popular technique to improve the performance of multilingual language models. This approach works by translating the input into English using an external machine translation system, and running inference over the translated input. However, these improvements can be attributed to the use of a separate translation system, which is typically trained on large amounts of parallel data not seen by the language model. In this work, we introduce a new approach called self-translate, which overcomes the need of an external translation system by leveraging the few-shot translation capabilities of multilingual language models. Experiments over 5 tasks show that self-translate consistently outperforms direct inference, demonstrating that language models are unable to leverage their full multilingual potential when prompted in non-English languages. Our code is available at https://github.com/juletx/self-translate.
