Causal Screening to Interpret Graph Neural Networks
Authors: Xiang Wang, Yingxin Wu, An Zhang, Xiangnan He, Tat-seng Chua
Keywords: Feature Attribution, Graph Neural Networks, Explainable Methods, Causal Effect
Abstract: With the growing success of graph neural networks (GNNs), the explainability of GNN is attracting considerable attention. However, current works on feature attribution, which frame explanation generation as attributing a prediction to the graph features, mostly focus on the statistical interpretability. They may struggle to distinguish causal and noncausal effects of features, and quantify redundancy among features, thus resulting in unsatisfactory explanations. In this work, we focus on the causal interpretability in GNNs and propose a method, Causal Screening, from the perspective of cause-effect. It incrementally selects a graph feature (i.e., edge) with large causal attribution, which is formulated as the individual causal effect on the model outcome. As a model-agnostic tool, Causal Screening can be used to generate faithful and concise explanations for any GNN model. Further, by conducting extensive experiments on three graph classiﬁcation datasets, we observe that Causal Screening achieves signiﬁcant improvements over state-of-the-art approaches w.r.t. two quantitative metrics: predictive accuracy, contrastivity, and safely passes sanity checks.