The reaction was predictable: Unbelievable. Couldn’t happen.

People speculated he must be a straight-laced Mormon, naive and unfamiliar with modern-day dating hazards. Or he must be part of an elaborate hoax designed to bolster his image. Because no big-time college football player, beloved on campus and adored by millions, could have a girlfriend he’s never … actually … met.

Yet even people who really ought to know better say what Notre Dame’s Manti Te’o says happened to him has happened to them, and they believe it happens far more often than people care to admit.

“If we shake the tree, we would find hundreds of thousands of people falling out of the tree who are experiencing something like this,” said Robert Epstein, a senior research psychologist at the California-based American Institute for Behavioral Research and Technology.

It’s just human nature, Epstein said, something known formally by psychologists as “confirmation bias.” We watch the news that matches our political beliefs. We discount viewpoints we don’t like. We ignore good advice and miss red flags, so we can continue believing in something we want to be true.

In Epstein’s case, it was believing he’d made a real connection with an attractive Russian woman named Ivana he met online. In fact, she was nothing more than a computer bot someone had set up to respond to queries on an online dating site.

“A lot of people still make fun of me,” he said.

Today’s social networking sites, such as Facebook and Twitter, make it easy to “meet” someone without ever doing more than chatting online or exchanging emails. The same tools that allow for such casual contact also can be used by impostors to create intricate personas that exist only on the Internet.

All of it simply makes it that much easier to delude ourselves.

“After a generation of kids growing up with Facebook and decades of online life, you’d think we wouldn’t be so easily duped, but I think these people who do the duping are more inventive than people who use the technology,” said Steve Jones, a communications professor and online expert at the University of Illinois at Chicago.

It’s been happening since people first began mingling in chat rooms more than 20 years ago. In 2006, one mom in Missouri, Lori Drew, created a MySpace page for non-existent teenage boy so she could “romance” – and strike back at – a girl she thought was spreading rumors about her daughter. Humiliated, the targeted girl later killed herself.

“As far back as the 1980s, men were impersonating women, kids were pretending to be adults, and all kinds of relationships with non-existent or phony people flourished online,” says Paul Levinson, a professor of communication and media studies at Fordham University, who studies social media.

Now, he says, “the rise of Twitter and Facebook have only made that easier.”

Those behind Te’o’s imaginary girlfriend, for instance, created more than one Twitter account for her and appear to have used photos lifted from a California woman’s Facebook page to make it look that much more real.

“In retrospect, I obviously should have been much more cautious,” Te’o said in a statement earlier in the week. “If anything good comes of this, I hope it is that others will be far more guarded when they engage with people online than I was.”

Te’o has company. As Notre Dame rose to No. 1 in the AP Top 25, sport writers nationwide recounted the story of the heroic, grieving athlete who persevered on the field after a girlfriend named Lennay Kekua was diagnosed with leukemia. Te’o and his family provided them with plenty of stories about the relationship, and no one figured out it was fiction until Deadspin.com broke that news this past week.

In his first interview since, Te’o told ESPN he had lied to his father about having met Kekua. To cover that up, he apparently lied to everyone else.

“That goes back to what I did with my dad. I knew that. I even knew that it was crazy that I was with somebody that I didn’t meet,” Te’o said during the off-camera interview Friday. “So I kind of tailored my stories to have people think that, yeah, he met her before she passed away.”

The fact is that many people don’t like to admit that they find love online, let alone that they might be misled by someone they’ve met that way.

For a young woman in Chicago, it started last February when a potential love interest responded to a personal ad she’d posted in the Craigslist “W4M” section. They communicated for several months online, first by email, and then instant messaging and then online voice chat.

She sent him her photo. He delayed sending his, again and again, and put off meeting in person. He wasn’t ready, he told her. It bothered her, but she was so taken with the ease and intimacy of their long, daily conversations – about their lives and their jobs, their family and friends, even sex.

After this went on for eight months, he abruptly deleted his email and Yahoo Messenger accounts, the only means she’d had to reach him. She didn’t even know his last name and wouldn’t know him if he passed her on the street.

“It all sounds ridiculous when you’re not immersed in the situation, but when you are, it’s incredibly easy to get sucked in and not want out,” said the 23-year-old, a young professional who shared her story on the condition of anonymity, still hesitant to admit how truly heartbroken she was over a person she’d never met in person.

Te’o offered similar details Friday, telling ESPN he never met Kekua face-to-face and when he tried to speak with her via Skype and video phone calls, the picture was blocked. Still, he said he didn’t figure out the ruse.

After he was told Kekua had died of leukemia in early September, Te’o admitted he misled the public about the nature of the “relationship” because he was uncomfortable saying it was purely an electronic romance. Skeptics remain, including some young adults accustomed to making connections on the Internet and by text message.

“Maybe I’d be more inclined to buy it if he was an everyday ‘Joe Schmoe,’ but with his fame, I can’t imagine it happening,” said Jennifer Marcus, a 26-year-old New Yorker who blogs about dating and other topics. “To me it seems like he did it for sympathy, or maybe has a few screws loose like a ton of people in this world. People go to great lengths to fit in.”

For the 23-year-old Chicagoan, her experience online hasn’t led her to swear off using Craigslist and the OkCupid website to find dates. She has, however, started heeding the red flags she once ignored, she says, and cuts off communication with anyone who won’t meet with her in person.

“I don’t want my time wasted again with someone who isn’t willing to give the same amount of transparency and availability that I am,” she said. “I’m planning a third date with someone who is very much the person he claimed to be.”