Perhaps one of the most important findings is that the fighters’ motivations tended to vary by their country of origin.

Foreign fighters in the sample from places like the United States and Western Europe were far more likely to be facing some sort of identity crisis, a desire for a personal sense of recognition that ISIS can provide. They were also more likely to be motivated by a rejection of Western culture. A story in The New York Times over the summer, titled “ISIS and the Lonely Young American” detailed how ISIS sympathizers made contact with a curious and socially isolated Westerner and then manufactured a sense of community and belonging through constant online interaction (not simply one-way messaging, as some have suggested).

People in the sample who joined ISIS or similar groups from another Muslim country, however, were far more motivated by the perceived plight of the Syrian Sunnis. For this group, the report found that “assisting Muslim ‘brothers’ and fighting the Assad regime are the most common catalysts (45 percent).” They were primarily thrill and status seekers.

The fact that joining ISIS or a similar group could improve one’s immediate social status underscores how differently ISIS is perceived in the Arab world than in the West.

Sunni fighters primarily from Syria and Iraq were also motivated by money and status. “Internal fighters believe they have a mission to defend their community (duty, Jihad) but they also have personal interests (money, staying alive),” according to the report.

It quotes one jihadist: “He asked me, ‘Why don’t you join us … leave your work and consider me your financier.’”

The Quantum study is not an exploration of “lone-wolf” attacks, which is what the San Bernardino shooting appears to be. And, of course, it doesn’t answer every question about the group’s appeal, nor specifically its appeal to Malik and Farook.

Farook had family roots in Pakistan but was a native citizen of the United States. Malik was born in Pakistan and reportedly had strong ties to Saudi Arabia. This suggests that the two embarked on different “paths toward radicalism.” And much about their motivation is still a mystery, and will likely remain so.

What the report does suggest, however, is that ISIS is not a monolith. It has various attractions to those who would join up or take action on its behalf. It’s unclear what the United States can do about the attraction of any group or cause to socially isolated individuals.

But the interviews with “internals” expose one of the organization’s most glaring vulnerabilities, especially in the way it recruits and deals with individuals on its home turf in Iraq and Syria. The fighters identified money as a significant motivator, as significant as jihad itself. This suggests that reducing ISIS’s ability to raise funds will decrease its allure. The group also identified the perceived persecution of Sunnis as a rallying cause. This suggests that Iraqi Security Forces who are Sunni, or Sunni rebels in Syria, could peel away at the group’s recruitment base in those areas.