How often do we pick up our cell phones "just to check" but look up and find it's half an hour later? We cannot break up with our cell phones. It's true. And when taking a break, many of us turn to cell phones. But it may not be a good thing for those who are doing mentally challenging tasks.

Using cell phone may result in poorer performance
During the experiment published in the Journal of Behavioral Addictions, 414 participants were given sets of 20 word puzzles. Halfway through, some students were allowed to take breaks using their cellphones, some took breaks using paper or a computer and others took no break at all.
Compared to people took no break, people using cellphones were slightly better solving puzzles than those who took no break.

Compared to people who took breaks using paper or a computer, people using cellphones:
—experienced the highest levels of mental depletion
—were least capable of solving the puzzles afterwards
Specifically, people using cellphones took 19% longer to do the rest of the task and solved 22% fewer problems than those using paper or a computer.
Why cell phones can affect you

Cellphones may have this affect because they may distract you in many different ways and make it difficult to focus your attention on your tasks.
When seeing your phone, you may want to check messages, contact friends, search information and so on, in ways that are different than using computers and laptops.