Mind the Gap... or Not? How Translation Errors and Evaluation Details Skew Multilingual Results
Summary
The paper asks whether the language gap that LLMs show on multilingual math benchmarks is real or a byproduct of flawed evaluation. The authors tested open models (Gemma 3, DeepSeek V3) and proprietary ones (Gemini, Claude, GPT) on MGSM, using the standard Kaggle prompt and its answer-extraction method. English accuracy was in the high 90s, but other languages fell behind, including high-resource French. This would normally suggest weak cross-lingual transfer.
Closer inspection showed two problems. First, the human translations contained subtle errors that changed the meaning of some problems. Second, extraction ignored local number formats, such as dot or space thousand separators and Bengali digits. The authors propose a semi-automatic quality-assurance procedure that uses strong models to flag suspicious items, and they recommend language-aware answer parsing. After both fixes, the gap mostly vanishes for the strongest models, which reverses the original conclusion. The work warns that benchmark quality and evaluation details can distort multilingual findings, especially when benchmarks approach saturation.
Key points
- MGSM consists of 250 grade-school problems drawn from GSM8K, which professional translators rendered into 10 typologically diverse languages: Bengali (bn), German (de), Spanish (es), French (fr), Japanese (ja), Russian (ru), Swahili (sw), Telugu (te), Thai (th) and Chinese (zh).
- With the original data, French showed large drops: 15.2% for Gemini 2.5 Pro and 17.6% for GPT5. These losses sometimes exceeded those for Swahili or Telugu, and the pattern was consistent across models.
- In one example error, a German translation turned "every second glass" into "each additional glass." This changes the correct numerical answer.
- The model setups were identical before and after the fixes; only the data and the answer extraction changed. The corrected dataset is released as MGSM-Rev2 on GitHub (google-research-datasets).
- The authors note several caveats:
- Gemini was used to translate and verify the corrections.
- The English source wording was slightly refined, so scores are not directly comparable with older MGSM results.
- Contamination of GSM8K remains possible.
- MGSM now looks saturated, so benchmarks with more headroom may still reveal real gaps.
Cite
@inproceedings{peter2026mind,
title = {{Mind the Gap... or Not? How Translation Errors and Evaluation Details Skew Multilingual Results}},
author = {Peter, Jan-Thorsten and Vilar, David and Domhan, Tobias and Malkin, Dan and Freitag, Markus},
booktitle = {Proceedings of the Fifth Workshop on Generation, Evaluation and Metrics (GEM)},
year = {2026},
doi = {10.18653/v1/2026.gem-main.22},
url = {https://doi.org/10.18653/v1/2026.gem-main.22}
}References
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