Estimating Causal Responsibility for Explaining Autonomous Behavior

There has been growing interest in causal explanations of stochastic, sequential decision-making systems. Structural causal models and causal reasoning offer several theoretical benefits when exact inference can be applied. Furthermore, users overwhelmingly prefer the resulting causal explanations over other state-of-the-art systems. In this work, we focus on one such method, MeanRESP, and its approximate versions that drastically reduce compute load and assign a responsibility score to each variable, which helps identify smaller sets of causes to be used as explanations. However, this method, and its approximate versions in particular, lack deeper theoretical analysis and broader empirical tests. To address these shortcomings, we provide three primary contributions. First, we offer several theoretical insights on the sample complexity and error rate of approximate MeanRESP. Second, we discuss several automated metrics for comparing explanations generated from approximate methods to those generated via exact methods. While we recognize the significance of user studies as the gold standard for evaluating explanations, our aim is to leverage the proposed metrics to systematically compare explanation-generation methods along important quantitative dimensions. Finally, we provide a more detailed discussion of MeanRESP and how its output under different definitions of responsibility compares to existing widely adopted methods that use Shapley values.