量化大模型社会的共识与极化，揭示真实社会动态的判断标准
When Is Emergent Consensus Real? A Measured Coupling Gain and a Validity Diagnostic for LLM Agent Societies
- 通过扰动邻居观点测量耦合增益gamma，量化模型间意见影响强度
- 发现主流大模型不会自发极化，极化需外部诱导，且仅在模拟中出现
- 提出随机初始条件诊断法，可区分真实共识与模型先验造成的假象
LLM“代理社会”常被用于研究涌现共识或极化现象，但缺乏可测量的控制参数、理论预测机制，也无有效方法判断结果是真实社会动态还是模型伪影。本文引入耦合增益gamma，通过反事实扰动邻接代理的观点进行测量。结果表明：（i）gamma值在五个前沿模型间稳定且具区分性（0.15–0.43），对改写不敏感；社交邻接与数值锚点的gamma相近，说明其反映的是信息耦合而非独特社会性。（ii）基于实测系数的经典动力学模型（如Friedkin-Johnsen、带符号拉普拉斯/结构平衡）能有效组织不同状态。（iii）前沿模型无自发回弹（beta ≤ 0），默认状态下不自极化；极化仅出现在FJ模拟中，未在真实代理中出现。（iv）提出随机初始条件诊断：最终与初始观点的斜率与偏移关系可区分真实平均与模型先验伪影（通过内部值事实排除边界截断）；应用于已发表的“涌现共识”研究（Chuang et al. 2023）显示，争议性议题存在平均，而确定性议题则为模型先验所致。（v）耦合具有情境依赖性：成对gamma无法预测多邻接结果（甚至顺序颠倒），而模态匹配的群体耦合可有效预测（16个封闭+开放模型，皮尔逊r=-0.70，置换检验p=0.008）。制度规律应基于目标互动中的匹配耦合，而非单邻接gamma。本文贡献测量协议与有效性工具，非新理论。
原文摘要 · Abstract (English)
LLM "agent societies" are studied via demonstrations of emergent consensus or polarization -- with no measurable control parameter, no theory of when each regime appears, and no test of whether an outcome is a genuine social dynamic or a model artifact. We introduce the coupling gain gamma, measured per-agent by counterfactually perturbing a neighbour's stated opinion. (i) gamma is stable and model-distinguishing -- across five frontier models it spans 0.15-0.43 (n=20, 95% CIs <= 0.025), paraphrase-invariant; social-neighbour gamma roughly equals numeric-anchor gamma, so gamma is evidence-coupling, not uniquely social. (ii) Classical dynamics with measured (not assumed) coefficients organise the regime: Friedkin-Johnsen for consensus/pluralism, signed-Laplacian/structural-balance for polarization. (iii) Frontier LLMs do not spontaneously backfire (beta <= 0), so default societies do not self-polarize -- polarization is always induced; the beta>0 branch arises only in the FJ surrogate, never in the agents. (iv) A randomized-initial-condition diagnostic -- the (slope, bias) of final vs. initial opinion -- separates genuine averaging from model-prior artifacts (boundary-censoring ruled out by construction via interior-valued facts); applied to a published "emergent consensus" result (Chuang et al. 2023) it reveals a model-specific conflation: averaging on debatable claims, prior-artifact on settled facts. (v) Coupling is context-dependent: pairwise gamma does not predict multi-neighbour outcomes -- it can order them backwards -- whereas a modality-matched group coupling does (sixteen closed+open models, Pearson r=-0.70, permutation p=0.008). The regime laws take this matched coupling, not the single-neighbour gamma: emergent consensus must be read from coupling in the target interaction. We contribute a measurement protocol and a validity instrument, not new theory.
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