Coarsening Causal DAG Models
Francisco Madaleno, Pratik Misra, Alex Markham
TL;DR
This work introduces coarsening as a principled method for causal abstraction, formalizing how a fine DAG $G=(V,E)$ can be mapped to a coarse DAG $G'=(V',E')$ via a surjection $\chi$ so that $\mathcal{M}(G) \subseteq \mathcal{M}(G')$ and enabling a lattice-theoretic view of possible abstractions. It defines interventional coarsening $G^{\mathcal{I}}$ by grouping nodes with identical $\mathcal{I}$-intervened-ancestor sets, proves identifiability under coarse Markov/faithfulness/interventional soundness, and provides a provably consistent algorithm that learns $G^{\mathcal{I}}$ from interventional data with unknown targets. The paper also explores two observationally grounded coarsenings—essential coarsenings (MEC-based) and marginal coarsenings (UEC-based)—and grounds the theory with synthetic and real-world experiments (e.g., a light-tunnel system), demonstrating accurate coarse-scale causal structure and substantial efficiency gains. The results offer a scalable pathway for causal discovery and interpretation across environments, enabling robust, high-level causal explanations when fine-grained modeling is impractical.
Abstract
Directed acyclic graphical (DAG) models are a powerful tool for representing causal relationships among jointly distributed random variables, especially concerning data from across different experimental settings. However, it is not always practical or desirable to estimate a causal model at the granularity of given features in a particular dataset. There is a growing body of research on causal abstraction to address such problems. We contribute to this line of research by (i) providing novel graphical identifiability results for practically-relevant interventional settings, (ii) proposing an efficient, provably consistent algorithm for directly learning abstract causal graphs from interventional data with unknown intervention targets, and (iii) uncovering theoretical insights about the lattice structure of the underlying search space, with connections to the field of causal discovery more generally. As proof of concept, we apply our algorithm on synthetic and real datasets with known ground truths, including measurements from a controlled physical system with interacting light intensity and polarization.
