发现大模型解释存在偏见,提出方法提升解释忠实度。
Faithful-Patchscopes: Understanding and Mitigating Model Bias in Hidden Representations Explanation of Large Language Models
- 用对比日志重校准抑制模型先验,强化上下文信息
- 在多个模型上使解释忠实度平均提升33%
- 适合关注模型可解释性与公平性的研究者
大语言模型通过Patchscopes框架可生成基于内部表示的人类可读解释,但我们的研究发现,模型在解码时倾向于依赖固有语言模式,掩盖了隐藏表示中的真实上下文信息。例如,即使隐藏表示编码了“紫色”这一属性,模型仍可能生成“绿色”,反映出强烈先验关联。为此,我们构建了一个评估数据集,结果显示在有偏情况下,解释忠实度平均下降18.84%。针对此问题,我们提出BALOR方法:将未打补丁提示的输出日志视为模型偏见,并与加入上下文补丁后的日志进行对比,通过重校准日志分布,抑制偏见、增强上下文信息。实验表明,BALOR在多个大模型上均显著优于现有基线,相对性能最高提升33%。
原文摘要 · Abstract (English)
Large Language Models (LLMs) have demonstrated strong capabilities for hidden representation interpretation through Patchscopes, a framework that uses LLMs themselves to generate human-readable explanations by decoding from internal hidden representations. However, our work shows that LLMs tend to rely on inherent linguistic patterns, which can override contextual information encoded in the hidden representations during decoding. For example, even when a hidden representation encodes the contextual attribute "purple" for "broccoli", LLMs still generate "green" in their explanations, reflecting a strong prior association. This behavior reveals a systematic unfaithfulness in Patchscopes. To systematically study this issue, we first designed a dataset to evaluate the faithfulness of Patchscopes under biased cases, and our results show that there is an 18.84\% faithfulness decrease on average. We then propose Bias Alignment through Logit Recalibration (BALOR), which treats the output logits from an unpatched prompt as capturing model bias and contrasts them with logits obtained under patched contextual information. By recalibrating the logit distribution through this contrast, BALOR suppresses model bias and amplifies contextual information during generation. Experiments across multiple LLMs demonstrate that BALOR consistently outperforms existing baselines, achieving up to 33\% relative performance improvement.
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