Last year, the average number of prime-time viewers age 12 to 34 fell 23 percent, to 834,000, compared with the same period a year earlier, according to Nielsen. (Jason Rzepka, senior vice president for brand communications and public affairs at MTV, pointed out that online streaming had affected nightly ratings, but that the channel remained the most watched basic cable channel among viewers 12 to 24.)

The new study, called “Young Millennials Will Keep Calm & Carry On,” comes at a turning point for MTV. “Jersey Shore,” the channel’s highest rated series ever, ended in December after six seasons. Around the same time, the channel began to notice shifts in behavior and tastes among younger viewers.

“Catfish: The TV Show,” a documentary series about online dating that had its premiere last year, emerged as a surprise hit with an average of 3.2 million viewers an episode and was the highest-rated premiere for an 11 p.m. series. MTV has attributed the show’s popularity, in part, to this younger demographic.

Alison Hillhouse, the vice president of MTV Insights who oversaw the study, said 14- to 17-year-olds were even more comfortable with social media and technology than their older siblings. She calls them “digital latchkey kids” because their hands-off Generation X parents have largely left them alone to navigate the Web.

Unlike the “Yes We Can” optimistic older millennials, this younger group of teenagers has a raised awareness of economic problems, MTV says.

“At age 13 they know they won’t find their dream job right away,” Ms. Hillhouse said. More than three-quarters of 14- to 17-year-olds interviewed said, “I worry about the negative impact that today’s economy will have on me or my future.”

Viacom, the parent company of MTV, is known for its in-depth audience research and for matching that research with marketers’ needs. MTV will take its latest findings to advertisers like Procter & Gamble, Unilever and Pepsi to help inform them about what type of ads will work on this more pragmatic group of teenagers.