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Facebook data reveals your best friends

Jan. 5, 2013 at 1:18 PM ET

NBC News file /
When researchers compared their model's predictions with the people Facebook users said they were closest to, the scientists found their model correctly predicted whether two people were close friends 84 percent of the time.

By Francie Diep, TechNewsDaily

Ever Facebook-stalked an ex to see whom he or she has been messaging with? It turns out that's an accurate way to measure how close two people are.

In a new study, researchers found that how often two people exchange publicly available wall posts, comments and pokes is a good measure of how close those two people say they are when asked. The correlation between wall posts and closeness means it's easy to identify people's best friends by crunching publicly available data. 

Social media companies and apps could use such data to spread "health and other positive interventions," the researchers wrote in a paper they published Jan. 4 in the journal PLOS ONE. Companies could send a message to one person in hopes she'll share it with her friends.

To learn about people's Facebook closeness, a team of data and social scientists from the University of California at San Diego and from Facebook wrote a model to predict how close two people are based on how often they interact on Facebook. "Interactions" included not only how often people liked and commented on each other's posts, but also how often they were tagged in the same photos. [SEE ALSO: 10 Ways to Protect Yourself on Social Media Websites]

The researchers then surveyed 789 English-speaking Facebook users, 96 percent of whom lived in the United States. The researchers asked survey takers to list the people with whom they had the closest relationships, including friends, family and neighbors. 

When the researchers compared their model's predictions with the people Facebook users said they were closest to, the scientists found their model correctly predicted whether two people were close friends 84 percent of the time. (If the model picked randomly, it would be correct 50 percent of the time.)

The researchers also learned a couple other interesting things: Having the same employer, school, age or gender listed didn't predict friendships as well as frequency of Facebook interactions. And private data about the number of private messages exchanged didn't help the model predict friendship any better than did publicly available data. 

The study findings support the idea that different methods of communication don't necessarily replace each other, the study authors wrote. In other words, people don't Facebook message their best friends less frequently because they see those friends face-to-face more often. Rather, people use all the communication tech available to them to keep in touch with their close friends.

These results also mean that social networking companies, apps and other organizations don't need to dig into people's private data in order to identify their closest friends to spread health tips, ads, games or whatever else from person to person, the researchers wrote. 

The new study supports other research showing that, in this digital age, it's easy figure out people's ties with one another. Previous studies have found that people's cellphone calls, tweets, LinkedIn data and Last.fm data all predict their real-life friends, uncovering a little bit of science behind how ideas, memes and other things go viral online.

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