A Universal Vibe? Finding and Controlling Language-Agnostic Informal Register with SAEs

Uri Z. Kialy, Avraham Shtarkberg, Ayal Klein


Abstract
While multilingual language models successfully transfer factual and syntactic knowledge across languages, it remains unclear whether they process culture-specific pragmatic registers, such as slang, as isolated language-specific memorizations or as unified, abstract concepts. We study this by probing the internal representations of Gemma-2-9B-IT using Sparse Autoencoders (SAEs) across three typologically diverse source languages: English, Hebrew, and Russian. To isolate pragmatic register processing from trivial lexical sensitivity, we introduce a novel dataset in which every target term is polysemous, appearing in both literal and informal contexts. We find that while much of the informal-register signal is distributed across language-specific features, a small but highly robust cross-linguistic core consistently emerges. This shared core forms a geometrically coherent “informal register subspace”, with greater geometric concentration at the deeper layer. Crucially, these shared representations are not merely correlational: activation steering with these features causally shifts output formality across all source languages and transfers zero-shot to six held-out languages spanning diverse language families and scripts. Together, these results provide the first mechanistic evidence that multilingual LLMs internalize informal register not just as surface-level heuristics, but as a portable, language-agnostic pragmatic abstraction.
Anthology ID:
2026.emnlp-main.2200
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:
50015–50032
Language:
URL:
https://aclanthology.org/2026.emnlp-main.2200/
DOI:
Bibkey:
Cite (ACL):
Uri Z. Kialy, Avraham Shtarkberg, and Ayal Klein. 2026. A Universal Vibe? Finding and Controlling Language-Agnostic Informal Register with SAEs. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 50015–50032, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
A Universal Vibe? Finding and Controlling Language-Agnostic Informal Register with SAEs (Kialy et al., EMNLP 2026)
Copy Citation:
PDF:
https://aclanthology.org/2026.emnlp-main.2200.pdf