Q. Facebook’s “People You May Know” suggested my landlady. How could it do that when we have no friends in common and I don’t have her in my contacts?
A. This question from a reader touched on an issue that’s left many Facebook users wondering: How does the social network’s friend-suggestion feature—sometimes called “PYMK” for short—identify potential friends?
Facebook’s documentation has often been a model of vagueness about the suggestions you may see on its “Find Friends” page, your News Feed or your notifications.
Until a few days ago, its help article said that “We show you people based on mutual friends, work and education information, networks you’re part of, contacts you’ve imported and many other factors.”
It now breaks out the following possibilities:
• “Having friends in common, or mutual friends. This is the most common reason for suggestions”
• “Being in the same Facebook group or being tagged in the same photo”
• “Your networks (example: your school, university or work)”
• “Contacts you've uploaded”
Facebook says a few other common theories about what drives People You May Know either no longer apply or never have.
First, your location history doesn’t factor into this. Facebook once used its record of where you’ve gone to inform PYMK, but it stopped after reporter Kashmir Hill asked about creepy cases of Facebooksuggesting such random people as a receptionist at a doctor’s office or strangers who frequented the same bars.
Second, Facebook doesn’t draw on who you e-mail or text. But if an e-mail app automatically adds people to your contacts(see, for example, older versions of Microsoft’s Outlook) and you then sync that address book to Facebook—something the company has long encouraged people to do—the same thing could happen.
In the same way, accepting another frequent Facebook suggestion by setting its Messenger mobile app to be your phone’s SMS app will not lead Facebook to check for who you text more often and factor that into PYMK’s advice.
Third, somebody else looking at your profile does not cause them to show up in these suggestions. To everybody who checked out an ex’s Facebook profile anytime recently: Take a moment to breathe a sigh of relief.
So what might have happened in this case?
There's a scenario Facebook’s help doesn’t spell out, but which the company confirmed can happen. The reader’s landlady added him to her contacts, then synced them to Facebook, and that sufficed to get the PYMK algorithm in gear.
Result: a friend suggestion whose basis is invisible to the person who received it.
Rob Pegoraro is a tech writer based out of Washington, D.C. To submit a tech question, e-mail Rob at [email protected] Follow him on Twitter at twitter.com/robpegoraro.
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