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Multilingual Language Models Encode Script Over Linguistic Structure

Paper · 2026 · Aastha A K Verma, Anwoy Chatterjee, Mehak Gupta et al.

Summary

Earlier studies found that multilingual LMs contain small groups of neurons that respond selectively to particular languages and can be manipulated to switch the output language. It remained unclear what these units actually capture. This paper asks whether they represent an abstract notion of language or surface cues such as the writing system.

The authors use LAPE, an entropy-based selectivity score, on two kinds of units: MLP neurons and SAE features (SAE-LAPE). They test Llama-3.2-1B, Llama-3-8B, Gemma-2-2B and Gemma-2-9B on languages written in Latin, Cyrillic, Devanagari, Perso-Arabic and logographic scripts. The experiments are:

  • romanizing non-Latin text,
  • shuffling word order,
  • probing units against lang2vec typological features,
  • causal interventions on selected units.

Romanized text activates units almost entirely separate from both the native-script units and the English units, even though the models translate romanized input well. Shuffling barely changes which units are selected. Typological information becomes easier to decode in deeper layers. However, generation relies most on units that stay stable under surface changes.

These results suggest that transliteration alone is a weak bridge for cross-lingual transfer. They may also explain why switching scripts can alter model behaviour, including safety responses.

Key points

  • A "unit" is either an MLP neuron or an SAE feature. Top-K SAEs from EleutherAI are used for Llama and JumpReLU SAEs (Lieberum et al., 2024) for Gemma. Main results are reported for Llama-3.2-1B, with Gemma-2-2B in the appendix and Llama-3-8B and Gemma-2-9B as scale checks.
  • Units are bound to script, not language. Native-script and romanized versions of the same non-Latin language (e.g., Hindi, Chinese) share very few language-associated units. Romanized inputs do not move toward English either, and this pattern persists in the 8B/9B models.
  • Shuffling word order has only a small effect on which units are identified. This points to lexical or orthographic statistics rather than syntax.
  • Typological structure from lang2vec becomes more decodable with depth. Still, no small set of neurons selectively controls it. Causal importance follows robustness to script and word-order perturbations, so the paper finds no single interlingua module.
  • Code is available at github.com/loadthecode0/multilingual-interpretability, together with romanized and shuffled versions of the evaluation sets. The analysis is limited to MLP activations, does not study training dynamics, and covers models of up to 9B parameters.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Institutions

Also on the byline: Indian Institute of Technology Delhi Abu Dhabi.

 Fields, topics and concepts

Cite

Cite as Aastha A K Verma, Anwoy Chatterjee, Mehak Gupta and Tanmoy Chakraborty. 2026. Multilingual Language Models Encode Script Over Linguistic Structure. Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers).

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/2026.acl-long.1554

@inproceedings{verma2026multilingual,
  title = {{Multilingual Language Models Encode Script Over Linguistic Structure}},
  author = {Aastha A K Verma, Anwoy Chatterjee, Mehak Gupta and Tanmoy Chakraborty},
  booktitle = {Proceedings of the 64th Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)},
  year = {2026},
  doi = {10.18653/v1/2026.acl-long.1554},
  url = {https://doi.org/10.18653/v1/2026.acl-long.1554}
}

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