Reasoning or Rambling? Exploring the Effect of Thinking on Agent Persuasion

Haodong Zhao, Jidong Li, Zhaomin Wu, Tianjie Ju, Zhuosheng Zhang, Bingsheng He, Gongshen Liu


Abstract
Understanding persuasion is critical for the safety and reliability of multi-agent systems built on large language models (LLMs). This paper studies persuasion dynamics by contrasting general LLMs with Large Reasoning Models (LRMs) that employ explicit "thinking" processes. Through large-scale experiments on objective (MMLU) and subjective (PersuasionBench and Perspectrum) tasks, we identify Persuasion Duality: reasoning enhances an agent’s persuasive power while simultaneously increasing its resistance to persuasion. For LRMs, adding thinking content increases persuasion rates by 21 pp on average, yet reduces susceptibility to incorrect persuasion by up to 10 pp on objective tasks. Despite these gains, we uncover a critical vulnerability: persuasiveness often stems from superficial cues such as response length and repetition rather than logical validity. Non-semantic padding or repeated conclusions can match or exceed the persuasive effect of coherent reasoning, revealing a strong length bias in agents’ judgments. We further show that persuasion propagates non-linearly in multi-hop agent chains, where intermediate agents may amplify or attenuate influence depending on task subjectivity. Finally, guided by attention analysis, we propose a prompt-level adversarial argument detection method that consistently improves agent robustness.
Anthology ID:
2026.findings-emnlp.189
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
4002–4025
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.189/
DOI:
Bibkey:
Cite (ACL):
Haodong Zhao, Jidong Li, Zhaomin Wu, Tianjie Ju, Zhuosheng Zhang, Bingsheng He, and Gongshen Liu. 2026. Reasoning or Rambling? Exploring the Effect of Thinking on Agent Persuasion. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 4002–4025, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Reasoning or Rambling? Exploring the Effect of Thinking on Agent Persuasion (Zhao et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.189.pdf