"Cellphones may have this effect 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," said Terri Kurtzberg, Associate Professor at Rutgers University in the US.
Published in the Journal of Behavioral Addictions, researchers analysed 414 college undergraduates who were asked to solve 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.
The participants who took phone breaks experienced the highest levels of mental depletion and were among the least capable of solving the puzzles afterwards.
Those who took a break on their cellphone took 19 per cent longer to do the rest of the task and solved 22 per cent fewer problems than those in the other break conditions combined.
Their post-break efficiency and quickness was comparable to those who took 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.