Nice article. I think the fact that testing if "X-caused-Y", by exploiting the fact that this is not symmetrical, has also been used by the "pseudo-causality"

Nice article. I think the fact that testing if "X-caused-Y", by exploiting the fact that this is not symmetrical, has also been used by the "pseudo-causality" Granger causality test: http://en.wikipedia.org/wiki/Granger_causality http://en.wikipedia.org/wiki/Granger_causality Also, causality in reality can be quite complicated if there are feedback loops: X-causes-Y-causes-X.