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It can take as little as 10 minutes for someone to go through your Facebook profile and predict how you’ll perform in the workplace.

In a new study to be published in the Journal of Applied Social Psychology, researchers asked a university professor and two students to spend 10 minutes looking through the Facebook profiles of employed college students. They were then asked a series of personality-related questions about those students, like whether they thought the students were dependable or emotionally stable.

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Six months later, the researchers obtained performance reviews of those students and compared those reviews with the earlier Facebook evaluations. The result: a high correlation between the perceptions drawn from Facebook profiles and their performance at work. In fact, the Facebook evaluations proved to be more accurate than traditional personality tests companies often use to gauge prospective employees.

One of the researchers, Donald Kluemper, told the Baltimore Sun:

“I think one of the differences is that you change the frame of reference. You’re asking the rater, ‘Is this person a hard worker?’ On a personality test, the employee would be asked, ‘How hard a worker are you?’ One of the criticisms of self-reporting personality testing is that it can be faked. On a Facebook page, that’s a lot harder to do.”

The study’s results call into question the sorts of personality tests human-resources (HR) staffs have used to evaluate candidates for years. If a 10-minute assessment is all it takes to determine good workers from poor ones, why wouldn’t all employers do that?

Well, a lot of them already are. An estimated 70% of recruiters and HR staffs have turned down candidates after they’ve found negative information about them from sites like Facebook.

But what’s interesting about this study is that it didn’t just focus on the kind of information that wouldn’t disqualify someone for a job. It also focused on positive personality traits that employers would want in an employee, like if he or she is social, curious, has interesting hobbies or a sense of humor. Photos of students going out and partying didn’t necessarily hurt them and sometimes even boosted their ratings because it showed that they were extroverted and comfortable in social settings.

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However, as more employers consider using social-media sites to evaluate job seekers, more companies could find themselves in legal limbo. The legality of using sites like Facebook in hiring is often unclear in many states, which is why many employers hire outside companies to run social-media background checks on candidates. Those companies give employers only the information that can legally be used in evaluating prospective employees.

So if you’re job-seeking, assume that a potential employer is looking you up online. Before you post something, think: Would I want my future boss to see this? But then again, don’t just post photos of you sitting around your apartment reading in complete solitude. Those photos showing you out and about may actually help you.