Title: Interpreting Blackbox Models via Model Extraction,
Abstract: Interpretability has become incredibly important as machine learning is
increasingly used to inform consequential decisions. We propose to construct
global explanations of complex, blackbox models in the form of a decision tree
approximating the original model---as long as the decision tree is a good
approximation, then it mirrors the computation performed by the blackbox model.
We devise a novel algorithm for extracting decision tree explanations that
actively samples new training points to avoid overfitting. We evaluate our
algorithm on a random forest to predict diabetes risk and a learned controller
for cart-pole. Compared to several baselines, our decision trees are both
substantially more accurate and equally or more interpretable based on a user
study. Finally, we describe several insights provided by our interpretations,
including a causal issue validated by a physician.