arXiv:2510.08158cs.CL2025-10被引 3

解决大模型过度拒绝问题,让回答更准确可靠。

Beyond Over-Refusal: Scenario-Based Diagnostics and Post-Hoc Mitigation for Exaggerated Refusals in LLMs

论文配图:Beyond Over-Refusal: Scenario-Based Diagnostics and Post-Hoc Mitigation for Exaggerated Refusals in LLMs
图 1 · 摘自论文原文
  • 设计双基准测试,识别导致错误拒绝的关键词与复杂对话场景。
  • 无需重训练,用三种轻量方法显著提升安全请求响应率。
  • 适合关注模型可靠性与实际应用落地的研究者和开发者。

大型语言模型(LLMs)常产生虚假拒绝,对包含类似不安全词汇的良性请求也予以拒绝。本文提出两个综合性评测基准:针对单轮提示的夸大安全基准(XSB),标注了诱发拒绝的“焦点”关键词;以及多轮情境式夸大安全基准(MS-XSB),系统评估模型在真实、上下文丰富的对话场景中的拒绝校准能力。实验发现,夸大拒绝现象普遍存在于多种近期大模型中,尤其在复杂多轮对话中更为严重。为缓解此类问题,本文利用后处理解释方法识别拒绝触发因素,并在推理阶段部署三种轻量、模型无关的策略——忽略词指令、提示重述和注意力引导,均无需重训练或参数访问。在四个指令微调的Llama模型上实验表明,这些方法显著提升了对安全请求的响应能力,同时保持强安全防护。研究建立可复现的诊断与缓解框架,为更安全、更实用的大模型部署提供可行路径。

原文摘要 · Abstract (English)

Large language models (LLMs) frequently produce false refusals, declining benign requests that contain terms resembling unsafe queries. We address this challenge by introducing two comprehensive benchmarks: the Exaggerated Safety Benchmark (XSB) for single-turn prompts, annotated with "Focus" keywords that identify refusal-inducing triggers, and the Multi-turn Scenario-based Exaggerated Safety Benchmark (MS-XSB), which systematically evaluates refusal calibration in realistic, context-rich dialog settings. Our benchmarks reveal that exaggerated refusals persist across diverse recent LLMs and are especially pronounced in complex, multi-turn scenarios. To mitigate these failures, we leverage post-hoc explanation methods to identify refusal triggers and deploy three lightweight, model-agnostic approaches, ignore-word instructions, prompt rephrasing, and attention steering, at inference time, all without retraining or parameter access. Experiments on four instruction-tuned Llama models demonstrate that these strategies substantially improve compliance on safe prompts while maintaining robust safety protections. Our findings establish a reproducible framework for diagnosing and mitigating exaggerated refusals, highlighting practical pathways to safer and more helpful LLM deployments.

大模型安全拒绝机制后处理优化

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