Nonlinear Causal Discovery with Additive Noise Models

by Patrik O. Hoyer, Dominik Janzing, Joris Mooij, Jonas Peters and Bernhard Scholkopf

This paper talks about making causal inference from data. We know if two r.v.s have an additive linear relationship (with noise), the reverse relationship also holds. If there is a non-linear relationship, our causal inference will be easier since the inverse might not hold. This is the main result of this paper, finding if there exists a reverse relationship, the probability must satisfy a differential equation. From this equation we know, if \nv''' = \xi''' = 0, where the two function are the logarithm of the PDF of x and the additive noise n, f must be linear.

This also suggests a way of making causal inference on DAGs. This leaves us to find a powerful regressor to capture the possible relationship between two r.v.s. The authors chooses GPR. Then the residue should be statistically independent of x, which can be tested with HSIC.

However, if we are to find the latent structure instead of doing a statistical test, this search will be intolerable if the DAG size is beyond 7.