A soldier patrols in the courtyard of the Louvre Museum in Paris, Tuesday, Nov. 17, 2015. France made an unprecedented demand on Tuesday for its European Union allies to support its military action against the Islamic State group as it launched new airstrikes on the militants’ Syrian stronghold. (AP Photo/Frank Augstein)

How will the Paris attacks influence French public opinion and affect its politics? Observers have speculated that France may get more militarily involved in in Syria, tighten its borders against migrants and refugees, or shift its political attitudes rightward.

We can offer insight from our research into American public reactions to the Sept. 11, 2001 terrorist attacks on the World Trade Center Towers and the Pentagon.

According to our findings, public opinion and future political events hinge on how the French react emotionally to the attacks. For example, we find that anxiety makes people less likely to support an aggressive military response–but anger makes them want to retaliate.

How we surveyed American public opinion after 9/11

After 9/11, we launched a national telephone survey of roughly 1,600 Americans. We systematically tracked public opinion for five months, from October 2001 to March 2002. Then in October 2002, during the lead-up to the Iraq war, we re-interviewed as many of the same people as we could so that we could better understand how 9/11 influenced American support for military action in Iraq.

In our survey, reported in more detail here, we asked Americans how often they had felt anxious, scared, worried and frightened in response to the 9/11 attacks. We asked these questions because one of terrorists’ central goals is thought to be to induce fear and anxiety within an affected public. Interestingly, for the most part, they failed.

Nationally, after 9/11, few Americans were anxious. But New Yorkers were more so.

Nationwide, only a minority of Americans reported that they often felt anxiety, or the associated psychological states of insomnia, depression, and difficulty concentrating. Anxiety was much more common among those who lived in the New York metro area or knew someone who had been killed in the attacks.

As we show in this paper, those who lived close to the attacks not only felt anxious but also changed their behavior to increase their personal safety. When we surveyed residents of Long Island and Queens in the New York metro area six to eight weeks after the attacks, we found that those who felt personally threatened by terrorism reported spending more time with their families, delaying or dropping plans to travel by air, and using public transportation less often in Manhattan since 9/11.

If that pattern holds, we expect Paris residents to feel more anxious, be more affected psychologically, and to act in more self-protective ways than those living elsewhere in France.

After 9/11, those who were anxious opposed U.S. attacks on Afghanistan.

Perhaps one of the most important political effects of anxiety after 9/11 was decreased support for U.S. military intervention in Afghanistan. The conventional wisdom is that politicians try to stir up fear to boost public support for military action. But anxiety actually decreased support, lowered President Bush’s approval ratings, and left people reluctant to have the U.S. get involved in foreign wars.

Twelve months later, anxious Americans were more opposed to military action in Iraq and thought intervention would be too risky for the U.S. economy and our relationships with allies, and would increase Middle East conflict.

Here’s why. As a general rule, anxiety makes people recoil from risk. A belligerent foreign policy makes people more aware of risks—and increases anxiety.

But more Americans were angry than were anxious.

But anxiety was not Americans’ overwhelming emotional response to the 9/11 attacks. Although most believed another terrorist attack was coming, they did not feel personally threatened or anxious.

But that perception of an imminent terrorist threat, when combined with anger at the terrorists, made Americans support an attack on Afghanistan (and, later, Iraq, although less strongly). Anger makes people want to strike back, often without considering the costs.

Those who believed that another terrorist attack was coming also supported a host of security crackdowns within the U.S., including limiting foreign visitors, intensely scrutinizing Arabs applying for a U.S. visa, placing Arab-Americans under special surveillance, adopting a national identification card, allowing the federal government to monitor Americans’ telephones and e-mails.

Why would anger outweigh anxiety?

Anxiety is a response to personal threat. Even after an attack as horrific as 9/11 or as last Friday’s attacks in Paris, a relatively small fraction of the population feels personally vulnerable to another such attack.

On the other hand, when an outgroup attacks a nation—whether that’s Islamist extremists or anyone else—people, especially those with strong national identities, get angry.

So what does all this mean for France in the coming weeks?

If the French public is anxious, France will likely oppose military action and disapprove of President Francois Hollande if goes to war.

But if, as in the US after 9/11, most of the French feel angry rather than anxious, the nation will probably back a foreign war in Syria, more domestic surveillance, recoil from and possibly attack immigrants, and tighten border control.

That’s what we predict. Hollande has already increased the bombing in Syria and declared a three-month state of emergency. We don’t expect the French citizenry to stand in his way.

Leonie Huddy is a professor of political science at Stony Brook University who studies public opinion from a psychological perspective. Stanley Feldman is a professor of political science at Stony Brook University who specializes in the study of political ideology and emotional reactions to politics. Their recent book is “Going to War in Iraq: When Citizens and the Press Matter.”