Using a smartphone while taking a break from mentally challenging tasks does not allow the brain to recharge effectively and may result in poorer performance, according to a study.
The research, published in the Journal of Behavioral Addictions, assigned 414 college undergraduates to solve challenging sets of word puzzles.
Halfway through, some were allowed to take breaks using their cellphones.
Others took breaks using paper or a computer while some took no break at all.
Researchers from the Rutgers University in the US found that the participants who took phone breaks experienced the highest levels of mental depletion and were among the least capable of solving the puzzles afterwards.
Their post-break efficiency and quickness was comparable to those with no break.
Their number of word problems solved after the break was slightly better than those who took no break, but worse than all other participants.
Participants who took a break on their cell phone took 19 per cent longer to do the rest of the task, and solved 22 per cent fewer problems than did those in the other break conditions combined.
"The act of reaching for your phone between tasks, or mid-task, is becoming more commonplace" said Terri Kurtzberg, an associate professor at Rutgers Business School.
"It is important to know the costs associated with reaching for this device during every spare minute. We assume it's no different from any other break -- but the phone may carry increasing levels of distraction that make it difficult to return focused attention to work tasks," said Kurtzberg.
"Cellphones may have this affect because even just seeing your phone activates thoughts of checking messages, connecting with people, access to ever-refilling information and more, in ways that are different than how we use other screens like computers, and laptops," she said.
The participants were given sets of 20 word puzzles.
Some were given a break halfway through, during which they were told to choose three items to buy within a specific budget, using either their cellphone, a paper circular or a computer.
They were told to type or write the reasons for their selections.