Signatures of Steerability in Activation Space of Language Models

Prajjwal Bhattarai, Tuka Alhanai


Abstract
Steering language models using a set of contrastive representations has been a canonical and computationally efficient method for controlling model behavior. Despite this success in controlling certain model behaviors, the effectiveness of activation steering varies markedly across concepts; the generalization properties of steering vectors are often considered a function of the dataset used to construct them. We make this dataset-dependence claim more rigorous and show that simple separation metrics strongly correlate with the downstream steerability of language models across diverse settings, even after controlling for layers and dataset effects. Beyond prediction, we provide evidence from a synthetic superposition experiment that separation metrics are strongly correlated with alignment between the empirical and true feature direction. Our results suggest that simple separability statistics can serve as practical diagnostics for when steering vectors are likely to work.
Anthology ID:
2026.aacl-short.18
Volume:
Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 2: Short Papers)
Month:
November
Year:
2026
Address:
Hengqin, China
Editors:
Yue Zhang, Ruifeng Xu, Ayu Purwarianti, Tong Rong, Jun Suzuki
Venues:
AACL | IJCNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
226–239
Language:
URL:
https://aclanthology.org/2026.aacl-short.18/
DOI:
Bibkey:
Cite (ACL):
Prajjwal Bhattarai and Tuka Alhanai. 2026. Signatures of Steerability in Activation Space of Language Models. In Proceedings of the 15th International Joint Conference on Natural Language Processing and the 5th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics (Volume 2: Short Papers), pages 226–239, Hengqin, China. Association for Computational Linguistics.
Cite (Informal):
Signatures of Steerability in Activation Space of Language Models (Bhattarai & Alhanai, AACL-IJCNLP 2026)
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PDF:
https://aclanthology.org/2026.aacl-short.18.pdf