"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," said one of the authors of the study.
"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.