提出大模型隐状态复用机制,解释为何推理会集体出错
Lifted State Hypothesis in Large Language Models

- 用可区分行为定义输入类型,共享隐状态支持泛化
- 同一类型中子类出现后,模型难以局部修正预测
- 适合研究模型推理一致性与错误传播的学者
大语言模型通过微调和上下文学习快速适应,但其对输入的等价判断机制尚不明确。本文提出提升状态假设:在固定参数、上下文范围和目标计算下,观测行为相似的样本构成计算相关类型。我们假设兼容的推理过程会激活一个可重用的潜在组件——提升状态,支持目标计算。状态复用带来类型级泛化,但也引发非单调修订问题:当后续证据区分出子类型时,仍共享父状态的修订可能影响本应保持不变的成员。模型需通过重路由、新状态或输入特异性补偿来分离子类型。我们形式化了泛化与修订之间的关系,并构建了NMR-Type数据集进行评估。该数据集首先支持广泛模运算规则,随后对隐藏子类型提供冲突监督并重播早期样本。在全量微调、LoRA和上下文学习中,模型常将广义规则推广至子类型,却无法实现后期局部修订。结果为假设提供了行为证据,推动对提升状态形成与修订机制的进一步研究。
原文摘要 · Abstract (English)
Large language models (LLMs) adapt rapidly through fine-tuning and in-context learning, yet it remains unclear which inputs they treat as the same case and why their predictions change together. We introduce the Lifted State Hypothesis. Under fixed model parameters, context scope, and target computation, samples indistinguishable in their observed computation-relevant behavior form a computation-relative type. We hypothesize that compatible episodes activate a reusable latent component---a lifted state---that supports the target computation. State reuse enables type-level generalization but creates a non-monotonic revision problem. When later evidence distinguishes a subtype, revising a state still shared with its parent may affect members whose predictions should remain unchanged. The model must separate the subtype through rerouting, a new state, or input-specific compensation. We formalize this relation between generalization and revision. We introduce the NMR-Type Dataset to evaluate LLMs. The dataset first supports a broad modulo rule. It then provides conflicting supervision for a withheld subtype while replaying earlier examples. Across full fine-tuning, LoRA, and in-context learning, models often generalize the broad rule to the subtype but fail to localize its later revision. These results provide behavioral evidence consistent with the hypothesis and motivate further study of lifted-state formation and revision.
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