Two weeks without mobile internet improved sustained attention
A preregistered randomized trial found blocking mobile internet for two weeks improved objectively measured sustained attention, mental health and well-being.
The short version
This is some of the strongest causal evidence yet that smartphones affect attention. In a preregistered randomized trial, adults who blocked mobile internet on their phones for two weeks — keeping calls and texts — improved on an objective test of sustained attention, as well as on mental health and well-being. The attention gain was the smallest of the three effects, and many participants did not stick to the block, but the direction was clear.
What the researchers did
Noah Castelo and colleagues recruited iPhone users in the US and Canada and randomly assigned them to two groups. One group installed an app that blocked all mobile internet for the first two weeks; the other group waited and blocked it for the following two weeks, which let them serve as a comparison. Internet on computers was not restricted. A total of 467 people enrolled, and 313 completed all three surveys.
Sustained attention was measured with a computer task that requires steady attention to gradually changing images and catching rare targets, alongside self-reports of attention lapses, mental health and well-being.
What they found
- Attention improved. Sustained attention scores rose during the block (a small effect, dz = 0.24). The authors compare its size to roughly ten years of typical age-related decline on that task.
- Mental health and well-being improved more. Effects on mental health (dz = 0.57) and well-being (dz = 0.46) were larger.
- Screen time halved. Daily phone screen time fell from about 314 to 161 minutes in the first group.
- Most people gained something. About 91% improved on at least one outcome.
- Where the time went. The well-being gains were partly explained by more time offline, socializing, exercising and outdoors. None of these explained the attention effect.
AARP's plain-language summary is a useful companion read.
Limits and caveats
Compliance was low: only about a quarter of those who signed up kept the block active for at least 10 of the 14 days, and people who finished the study started out healthier and more attentive than those who dropped out. Participants were motivated to cut back and knew what the study was about, so expectations may have played a part. Only iPhone users were eligible, the block lasted two weeks, and blocking all mobile internet is a blunt instrument — the authors suggest partial blocks as a middle ground, but those were not tested.
What it means for how you work
If your focus feels fragmented, a time-limited experiment with your phone is worth trying: switch off mobile data, or block the apps you reach for most, for two weeks, then compare how your focused work sessions go before and after. Keeping calls and texts on makes it practical. This complements smaller changes during the workday, like batching notifications (Fitz et al., 2019). Treat it as a test on yourself rather than a permanent rule.