The world isn't always the fairest place, and we don't always do the best job of taking care of each other.

Which is led to plenty of protests throughout history, from sit-ins to rallies outside government buildings. Most protests are pretty peaceful, but occasionally, they'll become destructive.

And for a long time, crowd psychologists have been trying to figure out why people will sometimes go a bit too far start flipping cars, and looting stores. It turns out that it has a lot to do with risk and group identity. Riots usually happen after months or years of social justice or political troubles — like the 2011 riots across England, which happened after years of tension between the public and the police.

Eventually, there's a catalyst — in that case, the police shooting of a man named Mark. Duggan — and it's the last straw that drives people to take to the streets. Still, just because a bunch of angry people gather doesn't mean there's necessarily going to be a riot.

Peaceful protests often involve groups of angry people, too. Every crowd is different, and there are multiple ways violence can start. In some cases, a riot happens because of some emotionally-charged risk assessment.

A few people quickly decide that the crowd is big enough and upset enough that, if they take violent action, everyone else will follow them. They also believe that there are enough people that the risk of arrest is low, so they might throw a rock through a window or help set a car on fire, and that's sometimes enough for others to do the same. In other cases, how the police handle a crowd can actually be the catalyst.

Most angry crowds are a mixed bag of both violent and peaceful people — generally, most people there don't want to actually cause destruction. Still, some studies have observed that the police often treat the entire crowd as dangerous, and when the police get hostile, that can sometimes be the spark that pushes peaceful members of the crowd over the edge. But no matter how the riot starts, there has to be something that causes the violence to continue.

You might have heard about an idea called deindividuation, where rioters stop thinking about their own moral code and blindly follow the crowd instead. They sort of lose their sense of self. A lot of psychologists used to think this happened to people during riots, because it does sound like it makes sense.

But decades of research didn't find much evidence for deindividuation during riots, and by the late 1990s, the idea had been pretty much discredited. Even though rioters may not make the best decisions, people don't become mindless, destructive zombies as soon as the first window breaks. Instead, they're often acting from a powerful sense of group identity.

Rioters are united by a strong set of values, and they often are united against the same thing, like a group in the government or another authority. So when riots break out, it's not because people lose all sense of self; instead, they're acting in what they see as the best interest of the group. Of course, riots are still made up of individuals, and some people will take advantage of the crowd to commit mindless violence.

But as a whole, people are consciously aware of the choices they're making during a riot, even if they aren't the safest choices. Since the crowd is so large and destructive, continuing to riot can feel like a pretty low risk for a while, but at some point — often because more police have arrived — it starts to feel like more of a danger. The best way to control a riot still isn't clear.

But the hope is that the threat of arrest will get so high that it'll break people's loyalty to the group, and they'll eventually clear the streets. The most obvious way to prevent the violence and destruction that comes from rioting would be to stop riots from starting in the first place, but there isn't really a foolproof way to do that. Some psychologists have suggested that authorities should be talking regularly with their communities so they don't feel they need to riot to make their voices heard.

But at the end of the day, there will probably be at least occasional riots forever until we do went up two things: we get rid of all the injustice in the world – not there yet, but sounds good, or we take away of the ability people to choose to do things – freedom is good so we don't wanna do that. So right now, the best we can do is to care for and support each other, and to try to make sure everyone's voice is heard. Thanks for watching this episode of SciShow Psych.

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