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arXiv 2602.01716cs.CL
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大语言模型中转向效果的机制指标

Mechanistic Indicators of Steering Effectiveness in Large Language Models

Mehdi Jafari, Hao Xue, Flora Salim

AI总结:

本研究通过分析大语言模型中转向效果的机制指标,探讨如何利用内部模型信号诊断转向可靠性,并提出新的评估基线以提升转向方法的性能。

摘要:

基于激活的转向使大型语言模型(LLMs)能够在不重新训练的情况下通过干预中间激活来表现出目标行为。尽管其广泛应用,但决定转向成功或失败的机制因素仍然理解不足,因为先前的工作主要依赖于黑盒输出或基于LLM的判断。在本研究中,我们探讨是否可以利用内部模型信号来诊断转向的可靠性。我们关注两种信息论度量:基于熵的归一化分支因子(NBF)以及在词汇空间中受控激活与目标概念之间的KL散度。我们假设有效的转向对应于解码步骤中结构化的熵保持和一致的KL对齐。基于一项显示两个架构不同的LLM之间高 inter-judge 一致性的可靠性研究,我们使用LLM生成的注释作为真实标签,并展示这些机制信号对识别成功转向和估计失败概率具有有意义的预测能力。我们进一步为对比激活添加(CAA)和稀疏自动编码器基于的转向引入了更强的评估基线,这两种是应用最广泛的激活转向方法。

英文摘要:

Activation-based steering enables Large Language Models (LLMs) to exhibit targeted behaviors by intervening on intermediate activations without retraining. Despite its widespread use, the mechanistic factors that govern when steering succeeds or fails remain poorly understood, as prior work has relied primarily on black-box outputs or LLM-based judges. In this study, we investigate whether the reliability of steering can be diagnosed using internal model signals. We focus on two information-theoretic measures: the entropy-derived Normalized Branching Factor (NBF), and the Kullback-Leibler (KL) divergence between steered activations and targeted concepts in the vocabulary space. We hypothesize that effective steering corresponds to structured entropy preservation and coherent KL alignment across decoding steps. Building on a reliability study demonstrating high inter-judge agreement between two architecturally distinct LLMs, we use LLM-generated annotations as ground truth and show that these mechanistic signals provide meaningful predictive power for identifying successful steering and estimating failure probability. We further introduce a stronger evaluation baseline for Contrastive Activation Addition (CAA) and Sparse Autoencoder-based steering, the two most widely adopted activation-steering methods.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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