People overattribute causality to a given stimulus when it is salient or the focus of their attention. We tend to conclude that someone is smart because he reads a lot. Or someone reads a lot because she is smart. But both events can also have the third cause or two separate causes for each one.
“Illusory correlation in interpersonal perception: A cognitive basis of stereotypic judgments” DL Hamilton, RK Gifford, Journal of Experimental Social Psychology, 1976