Bayesian Belief Layer for Controllable Opinion Dynamics in LLM Agents

Hafsa Akbar, Daniel Platnick, Marjan Alirezaie, Hossein Rahnama, Alex Pentland


Abstract
LLM agents in social simulation revise their opinions implicitly, in context: how open an agent is to persuasion can neither be specified nor verified, and collective outcomes inherit the model’s training prior. We introduce Bayesian Chronicle Agents (BCA), a minimal belief layer separating what an agent believes from how it speaks. Each stance is a probability, updated by one Bayesian step per utterance heard. A single prior-strength parameter 𝜅 encodes stubbornness, modeled after its role in Friedkin–Johnsen (FJ) opinion dynamics. We then sweep this parameter to yield three canonical regimes of opinion dynamics on demand (consensus, persistent disagreement, committed-minority influence), with persistent disagreement matching the FJ closed-form fixed points at R2 = 0.93–0.99. We further show that prescribed 𝜅 remains recoverable after the language round-trip, with perfect rank-order recovery across all four models. Explicit belief also makes simulation auditable: the layer surfaces systematic per-model stance biases that end-to-end simulation would silently absorb.
Anthology ID:
2026.realm-1.55
Volume:
Proceedings of the Second Workshop for REsearch on Agent Language Models (REALM 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Ehsan Kamalloo, Nicolas Gontier, Nikolai Rozanov, Maryam Hashemzadeh, Akhil Arora
Venues:
REALM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
807–815
Language:
URL:
https://aclanthology.org/2026.realm-1.55/
DOI:
Bibkey:
Cite (ACL):
Hafsa Akbar, Daniel Platnick, Marjan Alirezaie, Hossein Rahnama, and Alex Pentland. 2026. Bayesian Belief Layer for Controllable Opinion Dynamics in LLM Agents. In Proceedings of the Second Workshop for REsearch on Agent Language Models (REALM 2026), pages 807–815, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Bayesian Belief Layer for Controllable Opinion Dynamics in LLM Agents (Akbar et al., REALM 2026)
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PDF:
https://aclanthology.org/2026.realm-1.55.pdf