Argue about protests, and pretty soon you’re arguing about cameras.

Look at Missouri. On Monday, a video was posted to YouTube that appeared to show student and faculty protestors physically blocking journalists from entering a public quad. An assistant professor of mass media was captured shouting: “Who wants to help me get this reporter out of here? I need some muscle over here.” (She has since apologized.) The power of what was captured on film converted what had been a triumphant story of dissent into a national forum on media rights and ethics.

Or look at Yale. One of the first artifacts of those demonstrations showed an emotional student there yelling at a calmer school administrator. Supporters of the students rushed in to provide context for the short clip: “Don’t be too quick to judge,” wrote Sally Kohn of CNN.

It’s easy to blame these two controversies on networked photography: the twinned phenomena of Internet-connected cameras, wielded both by journalists and amateurs, and the ubiquitous screens needed to view their products. But media has played a role in every large-scale U.S. protest movement since, well, Common Sense. Television played a famously outsize (though not always positive) role in the midcentury civil-rights movement. And cameras, generally, do odd things to movements as physically limited as campus movements are: Protests are helpless to the power they gain through the camera.

So I wanted some historical perspective. How have recordings shaped previous student movements? I sought out Angus Johnston, a professor of history at the City University of New York and a leading chronicler of student activism. I spoke to him about how recordings have driven public perception of campus protests in the past. (Our conversation also spawned another story, too, about why American students—unlike those elsewhere in the world—almost never boycott class or go on strike.) The interview that follows has been edited and condensed for clarity.

Angus Johnston: I think even the word “recording” is a little narrower than it needs to be. In a lot of ways, still photography has been really, really important, and I think more important than video. The two really big, crucial moments that leap to mind are one from the last few years and one from earlier.

The earlier one is Kent State. There happened to be a student reporter, actually, for the student newspaper, on campus, on the quad, at the time of the shooting. And so all the photography from the Kent State was taken by that one student. The image of the young woman with her arm stretched out kneeling on the ground—which is in some ways the iconic image of the 1960s student movement—that was taken by a student-newspaper reporter. He had contacts with the [Associated Press], it went out over the AP wire, and had a huge, huge impact.

In contrast, a few weeks later, there was a police shooting—a mass police shooting—at Jackson State University in Mississippi. That was a historically black college, and so media attention was lower for that reason as well. But in my research, one of the things that really leaped out at me was that that incident took place at night, and there weren’t any photographers around. I think that is part of the reason—not the whole reason, but part of the reason—why Kent State has entered our national memory as this sort of searing moment. You ask people what the day is that the 1960s ended, and often the answer is Kent State.

Meyer : Yeah, or Altamont?

Johnston: Or Altamont, sometimes, yeah. But Kent State is really, if you’re talking about the student Sixties, that’s the bookend. And I don’t think it would be if we didn’t have those photos.

Brian Nguyen / Reuters

The second one is the UC Davis pepper-spray incident a few years ago, where all the students were sitting down and the cop just casually walking by [used pepper-spray on them]. The reason I think that’s so significant is the UC Davis incident was the latest in a pretty long string of incidents of police violence against peaceful student protestors, particularly in California. There had been incidents where students were beaten with batons, where they were tased. There was a situation where a cop actually pulled a gun on a group of student protestors, and that was actually recorded on video.

I was writing on my blog at the time, and every time one of these incidents would happen, I was getting more and more upset, and more and more freaked out, frankly, because it was getting no media attention. The violence was escalating, and I really wasn’t sure that it wasn’t going to take a student dying to dial this back.

Then the pepper-spray incident happens. The amount of police violence against student protestors in the United States dropped dramatically after that, and it has stayed at a much lower level since then.

Meyer: You have that sense from watching media coverage, and paying attention?

Johnston: Yeah, the stuff that I track—police violence against protestors is one of the half dozen or dozen elements of the campus protest scene that I’ve got my antennae up for specifically. And it’s clear that there’s less of that happening. We do see, there’s fewer building occupations, which is often where the violence takes place. But even so, my sense is very powerfully that there’s clear circumstantial evidence that decisions have been made to change the rules of engagement. UC Davis is a big part of that.

Meyer: I remember UC Davis happening too at the end of a string of UC protests, too, which were both connected to what I think of as Occupy Oakland.

Johnston: The interesting thing about Occupy is that two years before 2011, there was a string of building occupations at UC and Cal State campuses, and they called themselves Occupy California. Occupy Wall Street was, in part, not completely, an outgrowth and extension of the California stuff. UC Davis was part of that—there was a tent encampment which was one of the Occupy tactics.

Meyer: Those protests, I recall—and this may be also what got picked up and what got coverage—I remember those protests being more economic and anti-austerity than the current string of protests, which are mostly race and gender-based.

Johnston: Each case it was a matter of proportion. If we’re looking at Occupy California, there were several of those actions which were explicitly around issues of racial inclusion, particularly at the Cal State campuses. And in addition to the austerity and tuition hikes and all that, some of them were demandless protests as well—student power in the university-type questions.

You’re right that we have seen a real increased focus on racial-justice-type issues. I would say, right now, if you’re looking at the broad sweep of American student protest in 2015, the three really big recurring issues are: racial violence, sexual assault and sexual harassment, and economic access to higher education.

Actually, [Thursday] is what organizers are calling the Million Student March, which is a nationwide series of protests and marches planned for months around free higher education.

Meyer: Does it feel like racial violence and sexual assault and sexual violence, does it feel like the profile of those has increased since 2012? I remember you said on Twitter that the current set of protests were more similar to 1965 than the later Sixties. As an alumnus of Northwestern, there were also a string of protests around the early ‘90s that for us were tied to Asian-American Studies, so they obviously had a racial or ethnic component. What’s your sense of the macro-cycles here? Is this a comparable moment?

Johnston: That’s a really interesting question. I was on campus in the early Nineties, and it’s very hard for me to compare my on-the-ground ant’s-eye view from 1991 to the sort of global view that I have now. But I can say a couple of things.

It’s really important to remember that there’s always student protest happening on campus. There has not been a semester in my lifetime when there haven’t been dozens of campus protests. And sometimes there are hundreds—but there’s always dozens. One of the things that’s different is how much media attention are they getting. Media attention both has the effect of making it feel like there’s more going on, and probably has the effect of making it be the case that there’s more going on.

It is clear that we are in an upswing right now. I think that the late ‘80s and early ‘90s are a really interesting moment of comparison, because what you have there is a fair amount of protest that is around racial and gender issues. That was the moment when people first started talking about political correctness.

Meyer: I was going to say, in some ways the rhetoric you see now is—especially the anti-protest rhetoric—tends to use a lot of those same tropes.

Johnston: It is a very similar kind of argument that are made against the protests, so that is definitely one of the components. I think another thing that’s a very big component was that the late ‘80s and early ‘90s, there were a lot of fights around tuition issues. We saw that all sorts of places around the country. Where I was in the SUNY system in New York, we were fighting tuition increases every year during that period. And CUNY saw huge anti-tuition protests in the ‘80s and ‘90s.

Another thing that’s an interesting point of comparison is that the mid to late ‘80s saw a big, big wave of anti-apartheid protests on the American campus, which I think have a lot in common with the recent organizing against sweatshops.

Meyer: And less so with divestment?

Johnston: So, the divestment stuff that’s been happening—it’s growing, but I would say that it doesn’t have the mass-movement feel to my subjective eye. You’re not really seeing big rallies of several hundred people calling for either Israel divestment or fossil-fuel divestment. The anti-apartheid protests were really, really large mass protests, in many cases involving students who were not committed activists.

Meyer: Thinking about it, I’m realizing it does not look like marriage equality, where you bring out the students for that who… show up for that issue and not much else.

Johnston: Right, right. I think that when we look at protests for sexual-assault policies on campus, we see a lot more large-scale rallies around that than we do around the divestment question.

Meyer: I want to go back to media for a second. One of the interesting things that happened at Missou on Monday [when protestors blocked journalists from entering the encampment] was that the story could become a media story because there was a recording of that fight. Are there other moments like that? In some ways, it’s tempting to make that a phone story, like a camera-phone story. But actually it remained a media story because [the student photographer] Tim Tai was just getting filmed by a different videographer.

Johnston: It wasn’t somebody using their cellphone to record it. It was a journalist—a student journalist, I believe, who apparently just lodged criminal charges against the professor today apparently.

There definitely are other examples of that. One that sticks out in my mind is that a few years ago there was a building takeover at the New School in downtown New York City. It was protests against Bob Kerrey, who was the president at the time. There was at least one incident where student livestream of their building occupation wound up capturing protestors using language that a lot of people off-campus found ridiculous. Being self-aggrandizing and various other things. And that video got them a lot of mostly local New York City-based media attention, I remember New York Magazine made a very big deal about it on their blog. It was a similar kind of a thing where people felt like: Just watch this video and it speaks for itself. It tells you all you need to know about these protests.