Save your energy for what matters.
A notification can impair attention even if you do not look at or touch your phone, by an amount comparable to taking a call or texting. Even resisting a phone sitting on the desk can leave less mental capacity available. People most dependent on their phones showed the largest drop.
Replace a vague intention with that concrete sentence. Across 94 tests, people using this format achieved goals more often, with a medium-to-large effect. The change is in how you state the plan, without extra spending or much effort.
The least regular fifth of sleepers had body clocks about 2.5 hours later than the most regular fifth—effectively living with persistent jet lag. More regular students also had better grades.
Two weeks at six hours a night produced cognitive impairment comparable to two nights without sleep. People did not fully notice: self-rated sleepiness rose in the first few days and then leveled off, with six-hour and four-hour sleepers reporting similar tiredness. Feeling that six hours is enough can itself reflect poor awareness of sleep loss.
Taking 400 mg of caffeine six hours before bed shortened objectively measured sleep by over an hour, although sleep diaries did not detect the difference. The pooled estimate suggests finishing an ordinary 107 mg coffee at least 8.8 hours before bedtime; for an 11 p.m. bedtime, that is about 2 p.m.
During a two-week comparison in the same people, the week limited to three email checks daily brought significantly less stress without fewer messages received or answered. Unrestricted checking averaged 15.5 times daily at baseline.
Interruptions averaging 2.8 seconds doubled subsequent step errors; 4.4 seconds tripled them. In field observation, returning to an interrupted activity took about 25 minutes, with two other activities in between. Interrupted people worked faster but felt more stressed, frustrated and strained.
Switching tasks slows responses and increases errors. Frequent users of several media streams had not trained themselves to multitask better; they performed worse on switching tests.
Reading a light-emitting screen before bed delayed sleep by about 10 minutes, suppressed melatonin by 55%, shifted the body clock over 1.5 hours later and left people sleepier and slower to become alert the next morning.
In 2025, Chinese residents averaged 6.97 hours of nighttime sleep and fell asleep around 00:10. Bedtime phone or tablet use was associated with over twice the odds of insufficient sleep and 2.7 times the odds of daytime sleepiness. Merely having a device in the bedroom showed similar associations.
Rested people quickly learned to avoid risky choices in a laboratory task. After two sleepless nights, they repeatedly chose riskier options, especially at older ages. This study did not measure losing only a few hours, but important decisions can wait until morning.
A ten-minute nap improved alertness immediately, with some effects lasting two and a half hours. Five minutes did little. Twenty minutes took over half an hour to help. Thirty minutes initially produced grogginess and worse performance than not napping.