If you're doing something challenging don't think you're giving yourself a break by looking at your cellphone. Rutgers University researchers found people who took breaks while completing a puzzle and looked at their cellphones showed the highest levels of mental depletion afterwards. They performed only slightly better than participants who took zero breaks, but worse than those who took breaks doing other things. Study co-author Terri Kurtzberg explains, "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."