Triggering Chain-of-Thought via Latent Feature Interventions in Large Language Models

Zhenghao He, Guangzhi Xiong, Bohan Liu, Sanchit Sinha, Aidong Zhang


Abstract
Chain-of-Thought (CoT) prompting often improves the reasoning performance of large language models (LLMs), but the internal signal that triggers this behavior remains poorly understood. Leveraging the sparse features captured by Sparse Autoencoders (SAEs), we propose a systematic framework to analyze and intervene on the internal representations of LLMs, identifying a small set of latent features that are linked to reasoning behavior and can be causally tested through targeted intervention. Across multiple model families and reasoning benchmarks, we show that steering a single reasoning-related latent feature can substantially induce reasoning behavior without explicit CoT prompting, achieving accuracy comparable to CoT. We further show that the identified features are not tied to particular wording patterns or verbosity, and confirm their causal role in reasoning through suppression experiments that impair performance even under CoT prompting. These results suggest that CoT prompting activates specific latent features to trigger reasoning, and that targeted intervention on these features offers an alternative pathway to elicit efficient reasoning behavior without explicit CoT prompting.
Anthology ID:
2026.emnlp-main.102
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:
2415–2432
Language:
URL:
https://aclanthology.org/2026.emnlp-main.102/
DOI:
Bibkey:
Cite (ACL):
Zhenghao He, Guangzhi Xiong, Bohan Liu, Sanchit Sinha, and Aidong Zhang. 2026. Triggering Chain-of-Thought via Latent Feature Interventions in Large Language Models. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 2415–2432, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Triggering Chain-of-Thought via Latent Feature Interventions in Large Language Models (He et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.102.pdf