The mere sight of your mobile phone can distract you - even if you are not using it.
Researchers at the University of Southern Maine found that when people are asked to do a complicated task they are less successful if their mobile is still out.
Those who put it in their pocket or their bag got on average 20 per cent higher in the test because they were more focused.
The findings suggest that when we need to do some work the best thing to do is not just turn your phone off - but put it away as well.
The researchers asked two groups of students to carry out two different attention-sapping tasks, one of which was trickier than the other.