According to START researcher John Horgan, recent ISIS recruit Joshua Van Haften is somewhat deviant from the normal westerner that seeks to join the Islamic State. While most recruits, summarized in this article, are younger (17-23) and easily manipulated, many of them tend to be dissatisfied or directionless in their current lives, like Van Haften.
A Department of Homeland Security Emeritus Center of Excellence led by the University of Maryland