Graham Dugoni was at a music festival in San Francisco in 2012 when he witnessed something that disturbed him. A man was dancing, uninhibited, perhaps drunk, losing himself in the moment. Some strangers thought it was funny, so they filmed it and uploaded it to YouTube.

It’s the kind of thing that happens a thousand times a day. But it bothered Dugoni. Traditionally, as he saw it, people at such festivals would come together to commune, to share a collective feeling that those not present would never be able to participate in (see: Woodstock, 1969, or any Grateful Dead show from the 1960s to the 1990s).

But now, everyone had a smartphone. You had to act cool. And that old group intimacy? It was gone.

“That was a keystone moment for me,” said Dugoni, 31, and it raised a key question. “What degree of privacy can we expect in a public sphere?”

The topic is complicated, but the answer he came up with was simple: Ditch the phones.

He founded a company, Yondr, whose small, gray pouches swallow phones and lock them away from the fingers and eyes of their addicted owners. Since it started in 2014, hundreds of thousands of the neoprene pouches have been used across North America, Europe and Australia.

People entering a school, courtroom, concert, medical facility, wedding or other event are asked to slip their phones into the pouches when they enter. Once locked, the phones stay with their owners until they are ready to leave the premises, and then the devices are released from their tiny prisons at an “unlocking base.” The pouches can be rented for a single event or on extended leases. They are now used in more than 600 U.S. schools.

The effects are immediate: At first, people seem agitated and unsure of what to do with their hands. But then they adjust. “In line at the concession stand, you’ll overhear people talking about the artist and the show, and then about the fact that they’re having this conversation because they don’t have phones,” Dugoni said. “You’ll see people fully engaged with each other talking, and the feel of it is radically different.”

At San Lorenzo High School in California, which this school year began requiring students to Yondr (yes, it’s a verb) their phones from the beginning of first period until the end of the last, the difference has been stark. Grades have gone up, and discipline problems have plummeted, said principal Allison Silvestri. Referrals for defiance and disrespect are down 82 percent, she said, adding that before Yondr, most of them stemmed from arguments between students and teachers over phone use in class.

There’s also another effect:

“The campus is really loud now,” Silvestri said. “Students are interacting, talking to each other, reading, kicking a ball, socializing — because they’re not standing in a circle texting each other.”

A college soccer player and jazz pianist with a keen interest in philosophy, Dugoni worked briefly in finance in Atlanta, which led him to investigate the nature of anxiety. Studying Soren Kierkegaard, Martin Heidegger and the German American philosopher Albert Borgmann taught him that stress about technology is not a new thing.

“The role of technology in society is something that people have been circling around for a long time,” he said. “It’s a source of unarticulated angst in our society, a deep-seated thing that no one knows how to address. So phones are a hyperbolic representation of a deep theme.”

Dugoni compares the advent of the smartphone with the development of the phonetic alphabet or the newspaper in its momentousness. “I don’t think people realize how radically different it is to be a human being with a phone in your pocket,” he said. “If it becomes something that’s going to hollow out the meaning in your life, that’s something we’re going to have to address. … All we’re saying is, step into a phone-free zone; see what that’s like for a while.”

At this point, more than three-quarters of adults in the United States possess a smartphone, according to the Pew Research Center. It has become “a path of least resistance,” Dugoni said, even as it erodes age-old group dynamics. “If you send a text to somebody who’s not in the room, what you’re doing is extending your energy and bringing someone else into the fold. If everybody is doing that, the energy gets extended to the point where the perspective is changed and you can’t really bring it back.”

Locking away phones has been the rule at Dave Chappelle shows for years, and people are increasingly being asked to Yondr at parties and other informal events, said Carla Sims, Chappelle’s publicist. In the absence of phones, performers “know they’re not going to be bombarded with requests for photos, and they’re not going to have a lot of cellphones in their face while they’re trying to do improv,” she said, adding that audience members also like not having everyone in front of them holding phones up.

In the end, Dugoni wants people to ask themselves: What is the point of all those instantaneous texts, shares and likes?

“If you think of this phone as the ultimate expression of technological efficiency where things are easier, cheaper, faster all the time, I think it comes down to what are the limits of a purely efficiency-driven mode of life? What people really enjoy has nothing to do with efficiency. You can play a melody faster, but that doesn’t make sense. What does it mean to be more efficient in our social interactions? Is that something we want? Does that make sense at all?”

Dugoni is not alone; even as smartphone saturation has increased, the cultural tide has been shifting, with studies linking happiness to less screen time, and former tech executives speaking out about technology’s addictive qualities. People’s response to Yondr has also become more positive, Dugoni said, adding, “The only people who weren’t positive about it were the people in Silicon Valley, which was how I knew it was a good idea.”

But some are better at using it than others. “In Scandinavia, people will be more rule followers, versus doing a show with a bunch of VIPs on a Friday night in L.A., where they’re more squirrelly and everyone is someone’s uncle” and therefore wants an exception to the no-phone rules, Dugoni said.

Perhaps ironically, those who embrace the concept most quickly are young people who don’t remember a world without cellphones. Dugoni sees people his age as a bridge between them and older people.

“I think my generation, the onus is on us to lay down a lifeline for kids coming up, because if you’re a young person coming up, if you’re a sensitive, sharp young person, you know something’s out of whack,” he said. “Can it have something to do with people interacting with a screen eight hours a day and the experiences you’re having not coming from your primary experience?”

Does he think people will one day look back on unfettered smartphone use in the way we now look at smoking on airplanes?

“That’s a great comparison, if a little loaded,” he said. What he’d like to see is not the disappearance of the devices but a change in the social etiquette regarding their use.

“So our grandkids will say, ‘Wait, you could take a picture of anyone anytime and post it wherever you wanted? Well, of course you can’t. That’s an invasion of privacy.’ ”