Stable Reasoning, Unstable Responses: Mitigating LLM Deception via Stability Asymmetry

Guoxi Zhang, Jiawei Chen, Tianzhuo Yang, Lang Qin, Juntao Dai, Yaodong Yang, Jingwei Yi


Abstract
As Large Language Models (LLMs) expand in capability and application scope, their trustworthiness becomes critical. A vital risk is intrinsic deception, wherein models strategically mislead users to achieve their own objectives. Existing alignment approaches based on chain-of-thought (CoT) monitoring supervise explicit reasoning traces. However, under optimization pressure, models are incentivized to conceal deceptive reasoning, rendering semantic supervision fundamentally unreliable. Grounded in cognitive psychology, we hypothesize that a deceptive LLM maintains a stable internal belief in its CoT while its external response remains fragile under perturbation. We term this phenomenon stability asymmetry and quantify it by measuring the contrast between internal CoT stability and external response stability under perturbation. Building on this structural signature, we propose the Stability Asymmetry Regularization (SAR), a novel alignment objective that penalizes this distributional asymmetry during reinforcement learning. Unlike CoT monitoring, SAR targets the statistical structure of model outputs, rendering it robust to semantic concealment. Extensive experiments confirm that stability asymmetry reliably identifies deceptive behavior, and that SAR effectively suppresses intrinsic deception without degrading general model capability.
Anthology ID:
2026.emnlp-main.1156
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:
26487–26511
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URL:
https://aclanthology.org/2026.emnlp-main.1156/
DOI:
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Cite (ACL):
Guoxi Zhang, Jiawei Chen, Tianzhuo Yang, Lang Qin, Juntao Dai, Yaodong Yang, and Jingwei Yi. 2026. Stable Reasoning, Unstable Responses: Mitigating LLM Deception via Stability Asymmetry. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 26487–26511, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Stable Reasoning, Unstable Responses: Mitigating LLM Deception via Stability Asymmetry (Zhang et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.1156.pdf