Mike Kemp / Getty Images

Everyone knows someone who met their spouse online. A friend of mine whom I hadn’t seen in years told me recently that she, too, met her husband on an Internet dating site. They’re happily married, just moved into a new house, and are now talking about starting a family.

When I asked her if she thought online matchmaking was a better way than offline dating to find guys who were more compatible with her — and, therefore, better husband material — she laughed. “No, because I couldn’t stand him when I first met him,” she says of her husband. She thought he was full of himself and rude during their first encounter. It definitely wasn’t love at first sight, she said — that took a while.

In other words, according to my friend, Internet dating is just as unpredictable as the non-digital version. You never know how things are going to evolve until they do. But the benefit, she says, is that dating online gives you access to a lot more people than you’d ordinarily ever get to meet — and that’s how she connected with her future husband.

These observations have been borne out in a new study by social psychologists collaborating across the country. The extensive new study published in the journal Psychological Science in the Public Interest sought to answer some critical questions about online dating, an increasingly popular trend that may now account for 1 out of every 5 new relationships formed: fundamentally, how does online dating differ from traditional, face-to-face encounters? And, importantly, does it lead to more successful romantic relationships?

(MORE: How Do I Love Thee? Let Me Tweet the Ways)

For their 64-page report, the authors reviewed more than 400 studies and surveys on the subject, delving into questions such as whether scientific algorithms — including those used by sites like eHarmony, PerfectMatch and Chemistry to match people according to similarities — can really lead to better and more lasting relationships (no); whether the benefits of endless mate choices online have limits (yes); and whether communicating online by trading photos and emails before meeting in person can promote stronger connections (yes, to a certain extent).

Overall, the study found, Internet dating is a good thing, especially for singles who don’t otherwise have many opportunities to meet people. The industry has been successful, of course — and popular: while only 3% of Americans reported meeting their partners online in 2005, that figure had risen to 22% for heterosexual couples and 6% for same-sex couples by 2007-09. Digital dating is now the second most common way that couples get together, after meeting through friends. But there are certain properties of online dating that actually work against love-seekers, the researchers found, making it no more effective than traditional dating for finding a happy relationship.

“There is no reason to believe that online dating improves romantic outcomes,” says Harry Reis, a professor of psychology at University of Rochester and one of the study’s co-authors. “It may yet, and someday some service might provide good data to show it can, but there is certainly no evidence to that right now.”

One downside to Internet dating has to do with one of its defining characteristics: the profile. In the real world, it takes days or even weeks for the mating dance to unfold, as people learn each other’s likes and dislikes and stumble through the awkward but often rewarding process of finding common ground. Online, that process is telescoped and front-loaded, packaged into a neat little digital profile, usually with an equally artificial video attached.

That leaves a) less mystery and surprise when singles meet face to face. That’s not necessarily a bad thing, as profiles can help quickly weed out the obviously inappropriate or incompatible partners (who hasn’t wished for such a skip button on those disastrous real-life blind dates?), but it also means that some of the pleasure of dating, and building a relationship by learning to like a person, is also diluted.

It also means that b) people may unknowingly skip over potential mates for the wrong reasons. The person you see on paper doesn’t translate neatly to a real, live human being, and there’s no predicting or accounting for the chemistry you might feel with a person whose online profile was the opposite of what you thought you wanted. Offline, that kind of attraction would spark organically.

The authors of the study note that people are notoriously fickle about what’s important to them about potential dates. Most people cite attractiveness as key to a potential romantic connection when surveying profiles online, but once people meet face to face, it turns out that physical appeal doesn’t lead to more love connections for those who say it is an important factor than for those who say it isn’t. Once potential partners meet, in other words, other characteristics take precedence over the ones they thought were important.

“You can’t look at a piece of paper and know what it’s like to interact with someone,” says Reis. “Picking a partner is not the same as buying a pair of pants.”

(MORE: Online Dating Enjoying a Boom Among Boomers)

Making things harder, many sites now depend on — and heavily market — their supposedly scientific formulas for matching you with your soul mate based on similar characteristics or personality types. It may seem intuitively logical that people who share the same tastes or attitudes would be compatible, but love, in many cases, doesn’t work that way.

Some online dating sites, for example, attempt to predict attraction based on qualities like whether people prefer scuba diving to shopping, or reading to running, or whether they tend to be shy or more outgoing. But social science studies have found that such a priori predictors aren’t very accurate at all, and that the best prognosticators of how people will get along come from the encounters between them. In other words, it’s hard to tell whether Jim and Sue will be happy together simply by comparing a list of their preferences, perspectives and personality traits before they meet. Stronger predictors of possible romance include the tenor of their conversations, the subject of their discussions, or what they choose to do together.

“Interaction is a rich and complex process,” says Reis. “A partner is another human being, who has his or her own needs, wishes and priorities, and interacting with them can be a very, very complex process for which going through a list of characteristics isn’t useful.”

The authors also found that the sheer number of candidates that some sites provide their love-seeking singles — which can range from dozens to hundreds — can actually undermine the process of finding a suitable mate. The fact that candidates are screened via their profiles already sets up a judgmental, “shopping” mentality that can lead people to objectify their potential partners. Physical appearance and other intangible characteristics may certainly be part of the spark that brings two people together, but having to sift through hundreds of profiles may become overwhelming, forcing the looker to start making relationship decisions based on increasingly superficial and ultimately irrelevant criteria.

And remember, says Reis, “Online dating sites have a vested interest in your failure. If you succeed, the site loses two paying customers.”

Communicating online before meeting can help counter some of this mate-shopping effect, but it depends on how long people correspond electronically before taking things offline. A few weeks of email and photo exchanging serves to enhance people’s attraction when they finally meet, researchers found, but when the correspondence goes on too long — for six weeks — it skews people’s expectations and ends up lowering their attraction upon meeting. Over time, people start to form inflated or overly particular views about the other person, which leaves them at risk for being disappointed in the end.

Considering the many pitfalls, what accounts for the enduring popularity — and success — of online dating sites? Part of it may be the fact that singles who use online dating sites are a particularly motivated lot. Their desire to find a spouse and get married may make them more likely to actually find a life partner on the site, or believe that they have. And they’re also probably more likely to believe that the matchmaking algorithms that power so many sites really can find them that person who’s “meant to be.”

It also offers an attractive solution for an age-old problem for singles — where to meet potential mates. As more people delay marriage, either for financial or professional reasons, and with more people constantly moving around to find better jobs, disrupting their social networks, the easily accessed digital community of like-minded singles becomes a tantalizing draw.

Still, those who go online looking for love are left navigating a minefield of odds — not unlike dating in the non-digital realm. But at least there’s solace in matches like my friend’s. If there’s one thing online dating does better than any matchmaker or network of friends who are eager to set you up with that “someone who’s perfect for you,” it’s finding you lots and lots of candidates. “Like anything on the Internet, if you use online dating wisely, it can be a great advantage,” says Reis. You just have to accept that not all of your matches will be your Mr. or Ms. Right.

Alice Park is a writer at TIME. Find her on Twitter at @aliceparkny. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.