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arXiv 2402.13006cs.LGcs.CL
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研究模型不稳定性对解释和不确定性的影响

Investigating the Impact of Model Instability on Explanations and Uncertainty

University of Copenhagen(哥本哈根大学)

Sara Vera Marjanović, Isabelle Augenstein, Christina Lioma

AI总结:

本文通过在推理时引入噪声扰动,研究模型不稳定性对解释和不确定性的影响,发现高不确定性不一定意味着低解释合理性,且噪声增强模型在不确定时更擅长识别显著标记,同时显著性图鲁棒性可指示模型稳定性问题。

摘要:

可解释AI方法有助于理解模型行为,然而,对输入的微小且不可察觉的扰动会极大地扭曲解释。由于这些解释通常在模型部署前进行整体评估,因此很难判断特定解释何时是可信的。一些研究尝试为解释创建置信度估计器,但尚未有人调查不确定性与解释质量之间存在的联系。我们通过在推理时引入噪声,人为模拟文本输入中的认知不确定性。在这项大规模实证研究中,我们插入不同级别的噪声扰动,并测量其对预训练语言模型输出和不同不确定性指标的影响。真实的扰动对性能和解释的影响极小,但掩码却具有剧烈的影响。我们发现,高不确定性并不一定意味着低解释合理性;当训练过程中暴露于噪声时,这两个指标之间可能存在中等程度的正相关。这表明,噪声增强模型在不确定时可能更擅长识别显著标记。此外,当预测和认知不确定性度量过度自信时,显著性图对扰动的鲁棒性可以指示模型稳定性问题。Integrated Gradients对扰动表现出总体最大的鲁棒性,同时在性能中仍显示出特定于模型的模式;然而,这种现象仅限于较小的基于Transformer的语言模型。

英文摘要:

Explainable AI methods facilitate the understanding of model behaviour, yet, small, imperceptible perturbations to inputs can vastly distort explanations. As these explanations are typically evaluated holistically, before model deployment, it is difficult to assess when a particular explanation is trustworthy. Some studies have tried to create confidence estimators for explanations, but none have investigated an existing link between uncertainty and explanation quality. We artificially simulate epistemic uncertainty in text input by introducing noise at inference time. In this large-scale empirical study, we insert different levels of noise perturbations and measure the effect on the output of pre-trained language models and different uncertainty metrics. Realistic perturbations have minimal effect on performance and explanations, yet masking has a drastic effect. We find that high uncertainty doesn't necessarily imply low explanation plausibility; the correlation between the two metrics can be moderately positive when noise is exposed during the training process. This suggests that noise-augmented models may be better at identifying salient tokens when uncertain. Furthermore, when predictive and epistemic uncertainty measures are over-confident, the robustness of a saliency map to perturbation can indicate model stability issues. Integrated Gradients shows the overall greatest robustness to perturbation, while still showing model-specific patterns in performance; however, this phenomenon is limited to smaller Transformer-based language models.

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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