Umar Farouk Abdulmutallab, the Nigerian man accused of trying blow up Northwest Flight 253 to Detroit, is in many ways the very model of a modern terrorist.

Like many al-Qaeda members, he was raised in privileged circumstances and received a solid "modern'' education. No surprise there: As the forensic psychiatrist Marc Sageman found in his study of 172 al-Qaeda biographies, terrorists tend to come from stable, comfortable families. In a study of records on 404 members of violent Muslim groups around the world, Diego Gambetta and Steffen Hertog found nearly half had been to some sort of post-secondary educational institution (and since there were more than 100 militants on whom they couldn't get data, it's likely some in that group also went to college, making the percentage of educated terrorists even higher).

The anthropologist and media scholar Tom de Zengotita has offered a good explanation for the comfortable roots of most militants, I think. As he says, it's only in the global middle class that people feel entitled to make "lifestyle choices" from a menu that includes, among other things, religious fanaticism. Devout poor people don't grow up expecting to choose their faith; they just live it.

Secondly, like many other terrorists, too, Abdulmutallab apparently went through a period of loneliness and isolation, which, according to news reports so far, seems to have led him, via the Internet, to an al-Qaeda cell. That accords with Sageman's "bunch of guys" theory of recruitment: The militants he studied, he said in 2003, "felt isolated, lonely, and emotionally alienated." Friendships based on religion would assuage that feeling--and cut the "bunch of guys" off from other kinds of people.

Third, there is Abdulmutallab's field of study at University College, London: Mechanical engineering. Engineers are over-represented among Islamic terrorists--of the 17 9/11 hijackers with post-secondary diplomas, for instance, nearly half were engineers. In their study, Gambetta and Hertog found that 44 percent of Islamic militants with advanced degrees were engineers.

Gambetta, a sociologist, and Hertog, a political scientist, don't believe this is an accident. They have found a similar pattern in non-Islamic right-wing groups, they say. "A lot of piecemeal evidence,'' they wrote last summer, "suggests that characteristics such as greater intolerance of ambiguity, a belief that society can be made to work like clockwork, and dislike of democratic politics which involves compromise, are more common among engineers."