Years ago, it was a curmudgeonly rite of passage to brag that you could actually remember when MTV played music videos. But when today’s teenagers grow up, will they remember that MTV existed at all? The 34-year-old network, once a peerless purveyor of youth culture, has been struggling to retain its TV audience as younger viewers migrate to computers and mobile devices, and new research shows just how difficult the transition has been.

In the first quarter of 2015, ratings for MTV’s target demographic plummeted 29 percent compared to the same period last year. That’s according to Nielsen C3 data (live broadcasts plus three days of DVR playbacks) analyzed by the research firm MoffettNathanson, which reported the numbers Monday as part of a media preview. The report shows that MTV has lost ratings in its targeted demo for eight out of the last nine consecutive quarters, and in six of those quarters it suffered double-digit declines.

TV insiders say MTV has been particularly vulnerable to a shift in media habits that has viewers -- especially younger ones -- consuming more video on computers and mobile devices as opposed to cable. MTV targets 12- to 34-year-olds, and much of its audience barely remembers what life was like before the mobile revolution.

“Their audience is more technologically sophisticated than other networks,” said Barry Lowenthal, president of the Media Kitchen, a media-buying agency in New York. “They’re younger and they’re using their devices instead of watching TV.”

A spokesman for MTV agreed that the network is in a transitional era, but he said that’s exactly why the MoffettNathanson report doesn’t tell the whole story. Rather, he said MTV has been more aggressive than its peers in capturing viewers that Nielsen data doesn’t reflect, whether those viewers are consuming content online, through MTV’s mobile app or further back in the DVR playback window. “Our young audiences are leading all these trends and changing consumption, and a lot of that consumption outpaces measurement,” he said.

The comment echoes the stance of Philippe Dauman, chief executive of MTV’s parent company, Viacom Inc., who has been one of Nielsen’s most vocal critics in an industry growing increasingly frustrated with audience-measurement methods they say are too heavily focused on live or near-live TV viewing. As Variety reported this week, Viacom is currently in talks with select advertisers about alternative measurements.

Certainly, MTV’s success in capturing digital audiences bears out on social media. It has a Facebook fan base of almost 48 million, compared to 10 million for Fox News and 13 million for ESPN -- two networks that have much larger TV audiences.

Been Dead Before

Although last year was a challenging one for cable television as a whole, there is no denying that MTV is in the midst of a particularly punishing rut. Last month, a round of layoffs was reported following managerial restructuring at Viacom. The network hasn’t had a zeitgeist-defining hit since “Catfish” in 2013, and some of its latest efforts -- shows like the scripted thriller “Eye Candy” and the reality show “Virgin Territory” -- have lacked momentum and significant buzz. Its signature event, the MTV Video Music Awards, saw an 18 percent decline in viewership last year, as Billboard reported.

For some it’s a symptom of how difficult it is to capture a generation for whom pop culture and technology are intimately intertwined. “MTV has been the voice of a generation -- one that was connected through music and celebrities,” Lowenthal said. “But today young people are connected through their devices, which is driving down ratings across cable and broadcast. Given MTV’s core demo, it’s probably hitting them hardest.”

At the same time, commentators and critics have been proclaiming MTV’s irrelevance for decades, and each time the channel has proved a remarkable ability to reinvent itself, whether it was through pioneering reality shows like “The Real World” in the 1990s or train-wreck offerings like “Jersey Shore” in the 2000s.

More recently, the network has been planning its next shift -- a foray into larger-budget scripted shows more suited to audiences that gravitate toward high-quality series. Its adaptation of Wes Craven’s meta-horror classic “Scream” debuts in June, and the 10-episode sci-fi series “The Shannara Chronicles” is currently in production in New Zealand. MTV calls the shows huge bets and new territory for a network that is no stranger to new territory.

“Anybody who’s ever bet against MTV has been wrong,” the spokesman added. “We’ve always been able to come back and do it.”

Christopher Zara is a senior writer who covers media and culture. News tips? Email me here. Follow me on Twitter @christopherzara.