Apples to Apples? Towards Comparable Crosslingual Language Model Evaluation

Xiulin Yang, Ethan Gotlieb Wilcox, Catherine Arnett


Abstract
Crosslingual evaluation of language models that enables fair comparisons remains a fundamental challenge in multilingual NLP. Existing studies adopt a variety of downstream tasks and intrinsic metrics with different theoretical justifications, yet there has been little empirical investigation into whether these approaches yield meaningful crosslingual conclusions. We systematically examine crosslingual evaluation approaches using controlled monolingual language models trained on parallel data with varying tokenizer vocabulary sizes and model sizes, and further validate our findings on multilingual LLMs. We further discuss challenges in achieving comparable downstream evaluation across languages. Our results show that several widely used normalized metrics introduce crosslinguistic biases rooted in tokenization, encoding, and orthographic differences. In contrast, sentence-level negative log-likelihood computed over semantically equivalent sequences provides more meaningful and consistent crosslingual comparisons.
Anthology ID:
2026.emnlp-main.1724
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
39332–39351
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1724/
DOI:
Bibkey:
Cite (ACL):
Xiulin Yang, Ethan Gotlieb Wilcox, and Catherine Arnett. 2026. Apples to Apples? Towards Comparable Crosslingual Language Model Evaluation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 39332–39351, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Apples to Apples? Towards Comparable Crosslingual Language Model Evaluation (Yang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1724.pdf