Learning Bidirectional Causal Interactions with Heteroscedastic Neural Networks
Traditional methods struggle to identify bidirectional causal relationships between endogenous variables from observational data. This work proposes SEM-DNN, a novel approach that integrates conditional heteroskedasticity structures with deep neural networks to jointly model nonlinear structural equations and variance dependencies in disturbance terms. By enforcing diagonalization of the conditional covariance matrix, the method achieves identification of bidirectional causality without requiring instrumental variables, thereby guaranteeing unique identifiability of structural parameters. SEM-DNN substantially outperforms existing parametric, kernel-based, and decoupled neural network methods under conditions of nonlinearity, high-dimensional confounding, and non-Gaussian disturbances. Empirical application to price–sales feedback analysis in breakfast cereals demonstrates both its causal identification capability and the effectiveness of residual diagonalization.