Nothing seems to be a good predictor of whether or not someone turns to extreme political violence, though there are a few interesting themes amongst those who do...
The jihadi employment form asked the recruits, on a scale of 1 to 3, to rate their knowledge of Islam. And the Islamic State applicants, herded into a hangar somewhere at the Syria-Turkey border, turned out to be overwhelmingly ignorant.
The extremist group could hardly have hoped for better.
...
The findings address one of the most troubling questions about IS recruitment in the United States and Europe: Are disaffected people who understand Shariah more prone to radicalization? Or are those with little knowledge of Islam more susceptible to the group's radical ideas that promote violence?
The documents suggest the latter. The group preys on this religious ignorance, allowing extremists to impose a brand of Islam constructed to suit its goal of maximum territorial expansion and carnage as soon as recruits come under its sway.