Hofstra University didn't actually put a sign with a trigger warning outside the auditorium where the first debate of the general election was set to take place.

But tweets about the sign — which was actually placed outside a different Hostra event at the university's student center, one produced by MTV that featured virtual-reality artwork about gun violence and sexual assault — went viral anyway, perhaps because it was a too-perfect symbol of the clash between supporters and detractors of the famously politically incorrect Donald Trump.

"Trigger warning," it reads in large letters. "The event conducted just beyond this sign may contain triggering and/or offensive material. Sexual violence, sexual assault, and abuse are some topics mentioned at this event." It then listed on- and off-campus resources for anyone who might "feel triggered" as a result of what they saw.

To members of the media who haven't spent much time on college campuses recently, it was an unusual, even outlandish sight:

Sign inside Student Center at Hofstra. I guess these are common now on college campuses? #TriggerWarning pic.twitter.com/gfRkKVtToM — Tony Aiello (@AielloTV) September 26, 2016

Trigger warnings have played an outsize role in the debate about what's been called "the new political correctness" — whether greater sensitivity to students' concerns about mental health and racial and gender equality has turned into a threat to academic freedom and open debate. Critics argue that warning students that what they're studying could be "triggering" will make professors less likely to teach sensitive material and render students too emotionally fragile to deal with the real world.

Underlying this, though, is a larger — and perhaps more consequential — debate, about the relationship between college students and their colleges. College students, particularly those who are in their late teens and early 20s, are expected to act like adults while being supervised like children; as the price of college goes up, they're also increasingly seen as paying customers, and they're starting to act like it.

The argument about trigger warnings isn't just about trauma and mental health. It's about the demands students increasingly feel empowered to make and the confusion universities are facing in responding.

Why some people think trigger warnings help with trauma

Trigger warnings are meant to give people with post-traumatic stress disorder, and others who have experienced trauma, an idea of the content they're about to encounter. This is supposed to prepare those readers or viewers to cope with a significant, possibly debilitating, emotional reaction.

The terminology comes from post-traumatic stress disorder. People who have PTSD can experience flashbacks, anxiety, or nightmares, reliving a traumatic event when they see, smell, or feel something that triggers those memories. Anything can be a trigger, including sounds or smells. One classic example of a trigger is fireworks on the Fourth of July, which can startle and trigger flashbacks in veterans with PTSD from combat.

But avoiding triggers isn't considered a healthy coping mechanism for people with PTSD; in fact, it's a symptom of the disorder. A core purpose of therapy is making it possible for individuals to reduce their sensitivity to triggers. And there's no scientific evidence that trigger warnings help people avoid panic attacks or flashbacks in the short term — mostly because the issue hasn't been studied.

"Trigger warnings" first popped up on blogs and in online communities, especially those dealing with eating disorder recovery, self-harm, sexual violence, and, eventually, feminism and feminist politics in a broader context. Melissa McEwan, founder of the blog Shakesville, which uses trigger warnings, explained them in 2010:

Being triggered has a very specific meaning that relates to evoking a physical and/or emotional response to a survived trauma. To say, "I was triggered" is not to say, "I got my delicate fee-fees hurt." It is to say, "I had a significantly mood-altering experience of anxiety." Someone who is triggered may experience anything from a brief moment of dizziness, to a shortness of breath and a racing pulse, to a full-blown panic attack.

Of course, there's a core difference between a trigger warning on a blog and on a college syllabus: There's no consequence to skipping a blog post if you think it's going to upset you. College classes aren't nearly as voluntary or à la carte. Students don't always have the option of dropping a class or ignoring an assignment, at least not without suffering academic consequences.

That difference cuts both ways. To supporters of trigger warnings, it makes the warnings even more necessary, so that students can prepare themselves to deal with assignments that might give them severe anxiety. To opponents, trigger warnings could be a way for students to avoid doing those assignments altogether, making them ripe for misuse by students who don't have PTSD.

Why trigger warnings started showing up in college

Trigger warnings have spread to college amid growing concern about how to handle sexual assault on campus. PTSD is common among victims of sexual assault. A 2007 study in Virginia found women who had been sexually assaulted were nearly four times more likely to develop PTSD than those who had not; more than 30 percent of women who had been assaulted as adults met the diagnostic criteria for PTSD.

Studies estimate that about 20 percent of women experience sexual assault on campus. Those numbers are disputed, and not everyone who experiences trauma will go on to get PTSD. But it still suggests that college students are far more traumatized than many people might think.

Students began requesting trigger warnings as part of a broader debate about how colleges should handle sexual assault. The student government at the University of California Santa Barbara passed a resolution recommending trigger warnings. At Columbia, four students wrote an op-ed in favor of trigger warnings that started with an anecdote about a survivor of sexual assault reading Ovid's Metamorphoses:

As a survivor of sexual assault, the student described being triggered while reading such detailed accounts of rape throughout the work. However, the student said her professor focused on the beauty of the language and the splendor of the imagery when lecturing on the text. As a result, the student completely disengaged from the class discussion as a means of self-preservation. She did not feel safe in the class. When she approached her professor after class, the student said she was essentially dismissed, and her concerns were ignored.

In response to these concerns, some faculty have begun using trigger warnings voluntarily. They don't label every assignment with what could be potentially troublesome. Instead, they add a paragraph to their syllabus to acknowledge that students might have an emotional reaction to material covered in class, while leaving it up to the students themselves to research what might provoke those reactions.

Kelli Marshall, a lecturer at DePaul University who wrote for the Chronicle of Higher Education's Vitae blog about her teaching techniques, added this to her syllabus for a film class about Spike Lee and Quentin Tarantino:

Works of Lee and Tarantino contain extreme profanity, nudity, depictions of sex, and hate-speech (i.e., language that may be interpreted as racist, homophobic, misogynistic, or sexist). Their works also include representations, sometimes graphic, of the following: drug use and needles, overdoses, car accidents, insects, vomit, blood, medical procedures, corpses, trauma to a pregnant character, forced captivity, premature burial, torture, gun violence, bullet wounds, physical combat, murder, sexual assault, and rape. … Students who anticipate discomfort while screening these films should research the plot and potential triggers before class, and then sit near an exit so that, when necessary, they may step out of the room for a few minutes. Removing yourself for a moment or two is perfectly fine.

Oberlin College tried to go further. In late 2013, the college created a new policy for dealing with sexual assault and related issues. It recommended faculty "understand triggers, avoid unnecessary triggers, and provide trigger warnings," and to strongly consider making "triggering" material optional. If faculty chose to continue including triggering material, the policy recommended that they explain why they did so.

The policy created an outcry, including on campus, where professors felt blindsided. Its litany of possibly "triggering" material was mocked as overly politically correct. A few months later, the college tabled the trigger warning policy to be reworked; it hasn't yet been rewritten.

Why trigger warnings are particularly controversial in college

Oberlin's trigger warning policy might have been short-lived. But it kicked off a national debate that both mocked the idea of trigger warnings as overly politically correct and suggested that they were powerful enough to seriously harm higher education. "Now that they've entered university classrooms, it's only a matter of time before warnings are demanded for other grade levels," Jenny Jarvie wrote for the New Republic. "It's not inconceivable that they'll appear at the beginning of film screenings and at the entrance to art exhibits."

But Jarvie had it backward. Trigger warnings aren't in danger of sliding down to K-12 schools and movies. They're already there, and are trickling up to colleges.

Films have ratings that come with specific details about why they're rated that way. Modern art exhibits sometimes carry labels about provocative content. K-12 schools often let parents know if their children are exposed to sensitive material, and face criticism if they don't.

Trigger warnings, in other words, aren't uncommon for two groups of people: paying customers and children. This is doubly true when the paying customers are children. (Movie ratings and warnings about provocative art exhibits aren't generally aimed at adults' delicate sensitivities.) They're controversial in college because college students aren't supposed to be seen that way.

"The presumption that students need to be protected rather than challenged in a classroom is at once infantilizing and anti-intellectual," the American Association of University Professors wrote in August 2014. "It makes comfort a higher priority than intellectual engagement and — as the Oberlin list demonstrates — it singles out politically controversial topics like sex, race, class, capitalism, and colonialism for attention."

Underlying these objections are two big contradictions about the relationship between students and colleges:

College students are nominally adults, and so they shouldn't be infantilized. But they're also not seen as fully grown up, which is why college is relentlessly depicted, including by colleges themselves, as a coming-of-age experience. Students are paying an increasing amount for their education. But they're not quite considered consumers, either. Consumers can demand changes to the experiences they're paying for in order to make them happier or more comfortable. But happiness and comfort aren't the top priorities of education — they're not part of generating and passing along knowledge or developing critical thinking — and so students historically haven't been given much input to criticize how assignments and experiences make them feel.

But as higher education gets more expensive, that's been changing — colleges are adding amenities that students demand and are increasingly taking students' ratings of professors into account in tenure evaluations.

Trigger warnings are just a more overt example of a trend faculty members already fear: that making students uncomfortable is a route to student complaints, and student complaints have more power than they used to.

A college education isn't supposed to be a movie you can walk out of if you don't enjoy it, or a cruise ship you can get off if you're not having a good time. But colleges depend on students' tuition to keep their doors open. An increasing share of faculty members are adjuncts without the protection of tenure.

Anxiety about trigger warnings isn't always only trauma or sensitivity. It's about the power that comes with being a consumer, and how students are using it.