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You might have already guessed this if you clicked on this video, but we'll be mentioning topics that some people might be more sensitive to, like assault. That was a trigger warning.

You've probably seen them before— maybe on your film class syllabus last semester, giving people a heads up that one of the movies you'll watch has a graphic scene depicting an assault. Or in your sociology class, that you'll be discussing race-related violence. The idea behind trigger warnings is to let you know what's coming, so anyone who might find it more difficult because of their past experiences can avoid additional trauma.

Warnings like these have become one of the most divisive things on college campuses—and on the internet. Some people think they're important for creating safe and open spaces for everyone, while others believe they coddle people and stifle free speech. Those arguments have more to do with people's personal beliefs, so we won't get into them here.

But at their core, trigger warnings are about psychology, which can give you a more objective way of considering whether they're a good idea. It doesn't mean there's an obvious answer, though. The first thing to know is that triggers are very much a real thing for certain people.

Some of the core symptoms of post-traumatic stress disorder, or PTSD, are all about having a bad reaction to something that reminds a person of their trauma. That reaction can involve painful and distressing memories or flashbacks, where the person relives their trauma—what psychologists call intrusion symptoms. Sometimes these symptoms happen all on their own, but in many cases, certain words or images can serve as triggers.

So the goal of a trigger warning is to try and keep people with PTSD and related disorders from having to experience intrusion. The thing is, human brains can be strange. So while something obvious like a sexual assault scene in a movie might be a trigger for someone who's been sexually assaulted, it also might not.

Researchers have found that triggers are highly specific to people, and are often things from right before the traumatic event-- almost as if the brain is holding on to that information to protect itself. So, for example, one woman who was assaulted is triggered by doors, because her attacker stood in front of one right before the incident. In another case, a man who was in a horrible car crash is triggered by bright sunlight, since he saw bright lights just beforehand.

This is where trigger warnings, whatever you think of them, aren't going to help, because no one is going to think doors or sunny days at the beach require warnings. The triggers are just too idiosyncratic to predict. That doesn't mean there's no point in warning people about the more obvious ones, though.

One study found that the majority of assault victims with PTSD were triggered by images of assaults. And a separate study found that the most common triggers for shooting victims were things you might expect, like loud noises and sirens. So, it seems like the types of things we usually slap trigger warnings on aren't completely off base— although it's pretty clear they're not going to be able to prevent intrusion symptoms for everyone.

That, of course, assumes that trigger warnings work the way we want them to. And it's not clear whether giving people the chance to skip potentially triggering content is the right way to go. A hallmark symptom of PTSD is avoidance: basically doing all you can to avoid triggers so you don't have intrusion symptoms.

But the more avoidant someone is, the worse their PTSD symptoms usually are, and that avoidance is thought to be one reason why. At the same time, being triggered in class or anywhere else without any warning isn't likely to be helpful to people with PTSD. It might just make things worse.

One of the main PTSD treatments, exposure therapy, is based on having people think about their trauma on purpose. But it's done in a safe and trusting environment, with a therapist. That's a far cry from a classroom, where you might not feel comfortable and you're focusing on learning, not on trying to get better.

And when someone with PTSD actively chooses to think about their trauma, they usually don't have as severe a reaction as when they involuntarily recall a memory. Warnings make the situation more predictable. You also have more control, and the chance to try a coping strategy.

For all of these reasons, it's plausible that trigger warnings are effective. They could let people pass on things that they think will harm them more, while allowing them to choose to participate, but with all the information, so they're prepared. But it's also possible trigger warnings could be bad for people with PTSD.

Researchers have found that sometimes, warning messages can have unintended effects. For example, if people are told about a side effect of a medication, they'll often say they have it, even if they're given a placebo. That's called the nocebo effect.

And we know that expectations can change behavior in general. In a classic 1964 psychology experiment now known as the ‘panic button' study, researchers found that if you lead people to think something terrible will happen, they'll go along with it and hit a panic button, even if nothing's really happening. So it's possible that a warning about traumatic content is enough to serve as a trigger on its own.

The bottom line is that we simply don't know yet. Trigger warnings haven't been studied in any rigorous way, so we don't know, for example, whether students in classes that give trigger warnings have better outcomes compared to those that don't. In the meantime, it mostly comes down to whether you think the benefits of warning people are worth the risk of the nocebo effect.

Thanks for watching this episode of SciShow Psych! For more on what science has to say about tough questions like these, just go to youtube.com/scishowpsych and subscribe. [OUTRO ♪].