🤖 AI Summary
Conventional acyclic acyclic directed mixed graphs (ADMGs) fail to model cyclic causal structures prevalent in high-dimensional dynamical systems—e.g., economics, neuroscience, and control theory—where feedback loops are intrinsic.
Method: This paper investigates macro-causal effect identification on clustered directed mixed graphs (C-DMGs) built over input-output structural causal models (ioSCMs) and general directed mixed graphs (DMGs), which explicitly accommodate cycles.
Contribution/Results: We establish, for the first time, the soundness and completeness of the do-calculus within this cyclic abstract graphical framework. We generalize non-identifiability criteria from acyclic to a broad subclass of cyclic DMGs. Furthermore, we develop a complete theoretical characterization of macro-causal effect identifiability in C-DMGs over DMGs. By lifting the acyclicity assumption, our work substantially extends the applicability of structural causal inference to realistic, feedback-rich, dynamic systems.
📝 Abstract
The do-calculus is a sound and complete tool for identifying causal effects in acyclic directed mixed graphs (ADMGs) induced by structural causal models (SCMs). However, in many real-world applications, especially in high-dimensional setting, constructing a fully specified ADMG is often infeasible. This limitation has led to growing interest in partially specified causal representations, particularly through cluster-directed mixed graphs (C-DMGs), which group variables into clusters and offer a more abstract yet practical view of causal dependencies. While these representations can include cycles, recent work has shown that the do-calculus remains sound and complete for identifying macro-level causal effects in C-DMGs over ADMGs under the assumption that all clusters size are greater than 1. Nevertheless, real-world systems often exhibit cyclic causal dynamics at the structural level. To account for this, input-output structural causal models (ioSCMs) have been introduced as a generalization of SCMs that allow for cycles. ioSCMs induce another type of graph structure known as a directed mixed graph (DMG). Analogous to the ADMG setting, one can define C-DMGs over DMGs as high-level representations of causal relations among clusters of variables. In this paper, we prove that, unlike in the ADMG setting, the do-calculus is unconditionally sound and complete for identifying macro causal effects in C-DMGs over DMGs. Furthermore, we show that the graphical criteria for non-identifiability of macro causal effects previously established C-DMGs over ADMGs naturally extends to a subset of C-DMGs over DMGs.