Cross-Lingual Transfer and Shared Geometry of Deception Probes in LLMs

Matheus Prado Miranda, Marcelo Sartori Locatelli, Virgilio Almeida, Wagner Meira Jr.


Abstract
Linear probes can recover deception-related signals from large language model activations, but existing evidence is overwhelmingly English-centric. We investigate whether this discrimination transfers across languages and what representational geometry accompanies such transfer. We train instructed-deception probes on controlled honest/deceptive instruction contrasts in English, Portuguese, Spanish, German, and Chinese, and evaluate them without target-language refitting on a multilingual adaptation of DeceptionBench across five models spanning four different families. Cross-language performance remains close to matched-language baselines, with all models satisfying our prespecified noninferiority criterion, although absolute discrimination varies substantially across models. We also find that language-specific probe directions are strongly aligned and concentrate around a shared consensus direction, while response representations retain clear language-specific organization. Additional construct-validity analyses show that measurable response-level cues, including style, sentiment, factual truthfulness, and length, explain part but not all of the strongest probe discrimination. These findings together suggest that cross-lingual transfer and shared probe geometry can coexist with model-dependent detection quality and persistent language structure, indicating that representational alignment alone is insufficient evidence of reliable multilingual deception monitoring.
Anthology ID:
2026.mrl-1.33
Volume:
Proceedings of the 6th Workshop on Multilingual Representation Learning (MRL 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
David Ifeoluwa Adelani, Jesujoba Alabi, Catherine Arnett, Tyler Chang, C.M. Downey, Omer Goldman, Senyu Li, Lester James Validad Miranda, Jirui Qi, David Stap, Genta Indra Winata, Xinyu Crystina Zhang
Venues:
MRL | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
404–421
Language:
URL:
https://aclanthology.org/2026.mrl-1.33/
DOI:
Bibkey:
Cite (ACL):
Matheus Prado Miranda, Marcelo Sartori Locatelli, Virgilio Almeida, and Wagner Meira Jr.. 2026. Cross-Lingual Transfer and Shared Geometry of Deception Probes in LLMs. In Proceedings of the 6th Workshop on Multilingual Representation Learning (MRL 2026), pages 404–421, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Cross-Lingual Transfer and Shared Geometry of Deception Probes in LLMs (Miranda et al., MRL 2026)
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PDF:
https://aclanthology.org/2026.mrl-1.33.pdf