Unlocking the Spoken Style: Mechanistic Localization and Lightweight Control of Orality in LLMs

Zhigen Li, Yanmeng Wang, Jianxiang Peng, Yong Zhang, Dan Shi, Ning Cheng, Shaojun Wang, Deyi Xiong


Abstract
Voice agents typically use text-first pipeline for safety, but large language model (LLM) outputs are often overly written, making even high-quality text-to-speech (TTS) sound robotic. This is especially problematic in domains such as healthcare and sales, where different audiences require graded orality control. Text-level rewriting can control spoken style, but resources mostly study the reverse direction (spoken-to-written transfer), and its internal locus in LLMs remains unclear. We study English written-to-spoken rewriting with graded orality control. We introduce WSPairs, 4,709 written–spoken pairs from spontaneous conversations, annotated with 0–5 Orality Levels using seven sociolinguistic features. Through causal activation patching and head-level attribution, we find that orality concentrates in late layers and a sparse set of high-influence attention heads. We then propose CAS, a no-weight-update calibrated activation-steering method, and LAS, a learned activation-steering method. CAS improves exact level targeting and reduces bias relative to few-shot prompting, although target ordering remains imperfect at the highest levels. LAS uses 0.004%–0.006% trainable parameters, obtains higher Orality Level Accuracy (L-Acc) than full SFT on Qwen-3B and Mistral-7B, remains the strongest lightweight method on Llama-1B, and leads SFT by up to 3.9 L-Acc points out of domain. These results support localized, efficient control of text-level spoken style. Dataset and code are available.
Anthology ID:
2026.emnlp-main.381
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
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
8706–8726
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URL:
https://aclanthology.org/2026.emnlp-main.381/
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Cite (ACL):
Zhigen Li, Yanmeng Wang, Jianxiang Peng, Yong Zhang, Dan Shi, Ning Cheng, Shaojun Wang, and Deyi Xiong. 2026. Unlocking the Spoken Style: Mechanistic Localization and Lightweight Control of Orality in LLMs. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 8706–8726, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Unlocking the Spoken Style: Mechanistic Localization and Lightweight Control of Orality in LLMs (Li et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.381.pdf