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arXiv 2205.09620cs.LGcs.AI
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一种忠实性理论:连续数据上可微分类器的忠实性证明

Towards a Theory of Faithfulness: Faithful Explanations of Differentiable Classifiers over Continuous Data

Imperial College London(伦敦帝国学院)

Nico Potyka, Xiang Yin, Francesca Toni

摘要:

在文献中有广泛的共识,解释方法应该忠实于他们所解释的模型,但忠实仍然是一个相当模糊的术语。我们在连续数据的背景下重新审视忠诚度,并提出了两个正式的忠诚度定义的特征属性方法。定性的忠实性要求分数反映了模型上特征的真实定性效果(积极与消极),定量的忠实性要求分数的大小反映了真实的定量效果。我们讨论在何种条件下,这些要求可以满足到何种程度(本地与全球)。作为概念思想的一个应用,我们在连续数据上研究可微分类器,并将一致性分数描述为:每个定性忠实的特征属性方法在定性上等同于一致性分数。此外,如果属性方法在分类器的输出的变化与特征的分数成比例的意义上是定量忠实的,则它或者等同于梯度评分,或者它基于分类器的劣近似。为了说明理论的实际意义,我们通过实验证明,流行的归因方法可能无法在数据连续和分类器可区分的情况下给出忠实的解释。

英文摘要:

There is broad agreement in the literature that explanation methods should be faithful to the model that they explain, but faithfulness remains a rather vague term. We revisit faithfulness in the context of continuous data and propose two formal definitions of faithfulness for feature attribution methods. Qualitative faithfulness demands that scores reflect the true qualitative effect (positive vs. negative) of the feature on the model and quanitative faithfulness that the magnitude of scores reflect the true quantitative effect. We discuss under which conditions these requirements can be satisfied to which extent (local vs global). As an application of the conceptual idea, we look at differentiable classifiers over continuous data and characterize Gradient-scores as follows: every qualitatively faithful feature attribution method is qualitatively equivalent to Gradient-scores. Furthermore, if an attribution method is quantitatively faithful in the sense that changes of the output of the classifier are proportional to the scores of features, then it is either equivalent to gradient-scoring or it is based on an inferior approximation of the classifier. To illustrate the practical relevance of the theory, we experimentally demonstrate that popular attribution methods can fail to give faithful explanations in the setting where the data is continuous and the classifier differentiable.

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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