Chaotic in the sense of sensitive dependence upon initial conditions? Because human actions depend upon a large number of factors influenced heavily by their environment and their life experiences. It's far harder to find systems which are not chaotic than ones which are. Even the classical 3-body system interacting under gravitation is chaotic.

And while, yes, there is definitely good work being done in studying dynamic systems, applying those things to human beings is very difficult and dangerous. We already often face situations where humans are expected to conform to a limited set of predicted responses rather than the system being seen as flawed for failing to predict all possible responses. And human beings react very, very poorly to being restricted in these ways.