WASHINGTON » Catherine Devine had her first brush with an online bully in seventh grade, before she’d even ventured onto the Internet. Someone set up the screen name "devinegirl" and, posing as Catherine, sent her classmates instant messages full of trashy talk and lies. "They were making things up about me, and I was the most innocent 12-year-old ever," Devine remembers. "I hadn’t even kissed anybody yet."

As she grew up, Devine, now 22, learned to thrive in the electronic village. But like other young people, she occasionally stumbled into one of its dark alleys.

A new Associated Press-MTV poll of youth in their teens and early 20s finds that most of them — 56 percent — have been the target of some type of online taunting, harassment or bullying, a slight increase over just two years ago. A third say they’ve been involved in "sexting," the sharing of naked photos or videos of sexual activity. Among those in a relationship, 4 out of 10 say their partners have used computers or cellphones to abuse or control them.

Three-fourths of the young people said they consider these darker aspects of the online world, sometimes broadly called "digital abuse," a serious problem.

They’re not the only ones.

President Barack Obama brought students, parents and experts together at the White House in March to try to confront "cyberbullying." The Education Department sponsors an annual conference to help schools deal with it. Teen suicides linked to vicious online bullying have caused increasing worry in communities across the country.

Conduct that rises to the point of bullying is hard to define, but the AP-MTV poll of youth ages 14 to 24 showed plenty of rotten behavior online, and a perception that it’s increasing. The share of young people who frequently see people being mean to each other on social networking sites jumped to 55 percent, from 45 percent in 2009.

That may be partly because young people are spending more time than ever communicating electronically: 7 in 10 had logged into a social networking site in the previous week, and 8 in 10 had texted a friend.

"The Internet is an awesome resource," says Devine, "but sometimes it can be really negative and make things so much worse."

Devine, who lives on New York’s Long Island, experienced her share of online drama in high school and college: A friend passed around highly personal entries from Devine’s private electronic journal when she was 15. She left her Facebook account open on a University of Scranton library computer, and a prankster posted that she was pregnant (she wasn’t). Most upsetting, when she was 18 Devine succumbed to a boyfriend’s pressure to send a revealing photo of herself, and when they broke up he briefly raised the threat of embarrassing her with it.

"I didn’t realize the power he could have over me from that," Devine said. "I thought he’d just see it once and then delete it, like I had deleted it."

The Internet didn’t create the turmoil of the teen years and young adulthood — romantic breakups, bitter fights among best friends, jealous rivalries, teasing and bullying. But it does amplify it. Hurtful words that might have been shouted in the cafeteria, within earshot of a dozen people, now can be blasted to hundreds on Facebook.

"It’s worse online, because everybody sees it," said Tiffany Lyons, 24. "And once anything gets online you can’t get rid of it."

Plus, 75 percent of youth think people do or say things online that they wouldn’t do or say face to face.

The most common complaints were people spreading false rumors on Internet pages or by text message, or being downright mean online; more than a fifth of young people said each of those things had happened to them. Twenty percent saw someone take their electronic messages and share them without permission, and 16 percent said someone posted embarrassing pictures or video of them without their permission.

Some of these are one-time incidents; others cross into repeated harassment or bullying.

Sameer Hinduja, a cyberbullying researcher, said numerous recent studies taken together suggest a cyberbullying victimization rate of 20 to 25 percent for middle and high school students. Many of these same victims also suffer from in-person abuse. Likewise, many online aggressors are also real-world bullies.

"We are seeing offenders who are just jerks to people online and offline," said Hinduja, an associate professor of criminal justice at Florida Atlantic University and co-director of the Cyberbullying Research Center.

And computers and cellphones increase the reach of old-fashioned bullying.

"When I was bullied in middle school I could go home and slam my door and forget about it for a while," said Hinduja. "These kids can be accessed around the clock through technology. There’s really no escape."

"Sexting," or sending nude or sexual images, is more common among those over 18 than among minors. And it hasn’t shown much increase in the past two years. Perhaps young people are thinking twice before hitting "send" after publicity about adults — even members of Congress — losing their jobs over sexual images, and news stories of young teens risking child pornography charges if they’re caught.

Fifteen percent of young people had shared a nude photo of themselves in some way or another; that stood at 7 percent among teens and 19 percent among young adults. But almost a fourth of the younger group said they’d been exposed to sexting in some way, including seeing images someone else was showing around. And 37 percent of the young adults had some experience with "sexting" images.

Many young people don’t take sexting seriously, despite the potential consequences.

Alec Wilhelmi, 20, says girlfriends and girls who like him have sent sexual messages or pictures — usually photos of bare body parts that avoid showing faces. Once a friend made a sexual video with his girlfriend, and showed Wilhelmi on his cellphone.

"I thought that was funny, because I don’t know what kind of girl would allow that," said Wilhelmi, a freshman at Iowa State University.

Technology can facilitate dating abuse. Nearly three in 10 young people say their partner has checked up on them electronically multiple times per day or read their text messages without permission. Fourteen percent say they’ve experienced more abusive behavior from their partners, such as name-calling and mean messages via Internet or cellphone.

The AP-MTV poll was conducted Aug. 18-31 and involved online interviews with 1,355 people ages 14-24 nationwide. The margin of sampling error is plus or minus 3.8 percentage points.

The poll is part of an MTV campaign, "A Thin Line," aiming to stop the spread of digital abuse.

The survey was conducted by Knowledge Networks, which used traditional telephone and mail sampling methods to randomly recruit respondents. People selected who had no Internet access were given it for free.