IdioSteer: Controlling Figurative-vs-Literal Interpretation via Residual-Stream Activation Steering

Bar Cohen, Kai Golan Hashiloni, Kfir Bar


Abstract
Large language models (LLMs) default to figurative interpretations of idiomatic expressions when context supports them. We investigate whether this bias can be directly controlled via activation steering: asking whether idiomaticity is encoded as a manipulable direction in residual space. We introduce IdioSteer, a small controlled benchmark of 100 sentences across 20 idioms designed to expose interpretation-dependent generation. Using a steering vector applied to five LLMs from two model families, ranging from 2B to 12B parameters, we show that steering systematically shifts model outputs toward literal interpretations while preserving fluency. Three findings stand out: cross-layer steering, vectors from mid-to-late layers injected at early layers - consistently outperforms same-layer interventions; steering vectors transfer to held-out idioms; and effects replicate across architectures and model sizes using the same intervention protocol.
Anthology ID:
2026.emnlp-main.1251
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
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Pages:
28493–28531
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1251/
DOI:
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Cite (ACL):
Bar Cohen, Kai Golan Hashiloni, and Kfir Bar. 2026. IdioSteer: Controlling Figurative-vs-Literal Interpretation via Residual-Stream Activation Steering. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 28493–28531, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
IdioSteer: Controlling Figurative-vs-Literal Interpretation via Residual-Stream Activation Steering (Cohen et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.1251.pdf