When we published Friction in 2011, the book’s subtitle, “How conflict radicalizes them and us” was itself radical. Our idea was that not only the bad guys—the terrorists—but also good Americans can become radicalized. That “our people” could be anything like “them” threatened many Americans’ worldview. In today’s USA, seven years later, it is hard to deny radicalization is rising in America.

Consider the facts:

These statistics lay out radicalization in action. A similar picture emerges when considering radicalization of opinion in the USA.

Survey data show that hate for the other party has increased from about 17 percent of both Democrats and Republicans in 2000 to about 50 percent in 2016.

Radicalization is also evident in social interactions online: 2016 marked a sharp increase in hate speech, including anti-Semitic and anti-Muslim rhetoric on Twitter and Facebook. Although these social platforms have put in place policies and mechanisms to contain radical speech, there are alternative platforms (e. . GAB) that attract users precisely because they do not try to sanction hateful rhetoric.

A company specialized in attire and decals with radical messages was started in 2012; by 2016, it had expanded to a self-reported million customers.

Both in opinion and in action, the USA has transformed in the past few years. We are more radical now than we were before. Radicalization emerges out of conflict, not between Americans and terrorists, but between groups of Americans. Conflicts arise on the basis of , religion, sexual preference, and political party. How is this happening, and why is it happening now?

When Clark McCauley and I wrote Friction, we searched for mechanisms of radicalization that would reach beyond any particular group of terrorists. We studied case histories of terrorists from different religious, cultural, and historical backgrounds, ranging from anti-tsarist terrorists of the 1800s to Islamist terrorists of today. The 12 mechanisms of radicalization that we identified appear in the history of every terrorist group studied. This generality led us to expect that the same mechanisms would be found on both sides of escalating political conflicts, both old and new. Thus, Friction described how radicalization could be seen, not only in the terrorists but also in Americans responding to the terrorists.

Indeed, we see many of the same mechanisms of radicalization that lead to terrorism at work in U.S. today.

Status and motivate mass shooters like Las Vegas shooter Stephen Paddock, just as they motivate Islamist terrorists like Abu Musab al-Zarquawi. Personal grievance motivated incel (involuntarily celibate) Scott Paul Beierle, who shot several women at a yoga studio in Tallahassee, FL, just as it motivated some Palestinian bombers. Group polarization and group isolation and threat are at play on radical social media websites in the USA, leading one member to attack a synagogue in Pittsburgh, just as these mechanisms led Al Qaeda terrorists to the 9/11 attacks.

But it is mass radicalization observed in the USA that is the most striking. In Friction, we laid out three mechanisms of mass radicalization: Martyrdom, Jujitsu, and Hate. In the recent selection of a U.S. Supreme Court Justice, Brett Kavanaugh was a martyr for some and a monster for others. attacks immigrants to instigate Democratic counter-reaction and distract from his alleged connections with Russia (Jujitsu). Hate implies a bad essence, a belief in the other party’s bad essence causing many to want their children to marry within their party. “In 1958, 33 percent of Democrats wanted their daughters to marry a Democrat, and 25 percent of Republicans wanted their daughters to marry a Republican. But by 2016, 60 percent of Democrats and 63 percent of Republicans felt that way.”

The proliferation of social media offers an unprecedented window into mass psychology. It’s now possible to see a story spreading in real time, through the rate at which it is shared, commented on, or “liked.” It’s possible to see which social media profiles are more influential than others—by the number of their “followers” or “friends.” We can even track the effects a story, a tweet, or an image has on people­­­­––by reading their comments. People interacting on Facebook or Twitter don’t know each other personally. They are an imagined community, a part of another imagined community: a country, an ethnic group, a religion.

It has never been easier to observe mass radicalization in an imagined community. And it has never been easier to produce mass radicalization.

The Nazis, the Soviets, and the Chinese used propaganda to mass-radicalize their citizens. A traveling theatre, a staged street argument, a speaker, a film, a newspaper article—these could reach crowds, but the size of these crowds fades in comparison to the crowd that can access a viral story on Twitter. The difference between an effective radicalizing story then and now is hundreds versus millions exposed to it, days versus minutes for the exposure, and a handful versus hundreds sharing reactions to it.

This capacity can be exploited by foreign governments and domestic political players who benefit from fractionating the U.S. into conflicting groups. Private-sector research firms like Cambridge Analytica can harness the power of social media by collecting personal data of users and target-messaging content most likely to radicalize. Paid Internet trolls can instigate group divisions in fake social media posts.

Mass radicalization is a counterintuitive notion in a society where we are taught from a young age to take responsibility for our actions and have our own opinions. The last two years demonstrate that even in our individualistic society mass is at play, and mass radicalization is a real danger.