Cross-Lingual Alignment Without Joint Training: Do Monolingual Language Models Converge on Universal Representations?

Ej Zhou, Suchir Salhan, Catherine Arnett, Anna Korhonen


Abstract
Cross-lingual alignment in multilingual language models is typically attributed to joint training: shared parameters, mixed-language batches, or explicit alignment objectives. We ask whether monolingual models trained on non-parallel data learn alignable representations without joint training. By testing on strictly monolingual language models, such as the Goldfish model families and independently developed models from different research labs, we find three results. Correlation: these models develop alignable representational geometry across layers, with alignment strengthening as data scale, model scale, or linguistic proximity increases. Construction: a single Procrustes rotation fit on parallel sentences maps hidden states between models. Causation: the same rotation transfers functional content; patching a rotated English residual into a German model on a factual cloze flips the prediction to the donor’s capital in most cases. We confirm that cross-lingual alignment can emerge from the structure of language and the information it carries rather than from joint training, and this points to practical future directions including model stitching, merging, and modular multilingual systems built from monolingual components.
Anthology ID:
2026.emnlp-main.947
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:
21811–21837
Language:
URL:
https://aclanthology.org/2026.emnlp-main.947/
DOI:
Bibkey:
Cite (ACL):
Ej Zhou, Suchir Salhan, Catherine Arnett, and Anna Korhonen. 2026. Cross-Lingual Alignment Without Joint Training: Do Monolingual Language Models Converge on Universal Representations?. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 21811–21837, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Cross-Lingual Alignment Without Joint Training: Do Monolingual Language Models Converge on Universal Representations? (Zhou et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.947.pdf