LONDON, UK: Students who browse through social networking website Facebook during their study time obtain lower grades than those who don't.

A study has found that examination results of those who used the social website while working, even if it was on in the background, were 20 percent lower than non-users.

Researchers now say the study weakens the theory that young people's brains are better at multi-tasking, according to the Daily Mail.

Paul Kirschner, one of the authors of the study, said: "The problem is that most people have Facebook or other social networking sites, emails and maybe instant messaging constantly running in the background while they are carrying out other tasks."

"Our study, and other previous work, suggests that while people may think constant task-switching allows them to get more done in less time, the reality is that it extends the amount of time needed to carry out tasks and leads to more mistakes."

The research team studied 219 students aged between 19 and 54 at an American university.

Facebook users among them had a typical grade point average (GPA), a score from zero up to four, with an average of 3.06. Non-users had an average GPA of 3.82.

Those who did not use the site said they devoted more time to studying.

Three quarters of Facebook users said they didn't believe spending time on the website affected their academic performance.