You sit down to watch a film you've wanted to see for weeks. Ten minutes in, you're also on your phone. You try to read a few pages of a book and your eyes slide off the words. Meanwhile, you can watch forty 20-second videos without blinking. What's going on with our focus?
Short videos, fast rewards
TikTok, Reels and Shorts all work the same way: a clip of a few seconds, then another, then another. Each swipe brings something new, so the "is this good?" question gets answered every few seconds. Many researchers suspect that a steady diet of this trains us to expect a payoff almost instantly. Then slower things, like a lecture, a long article or a conversation, start to feel unbearably dull. That idea is still being tested, but the early evidence is hard to ignore.
The biggest study so far
In 2025, the journal Psychological Bulletin published a review of 71 studies with almost 100,000 participants on short-form video. Heavier use was linked to poorer thinking skills overall, and the strongest links were with:
Attention (staying focused) and inhibitory control (your ability to stop yourself, for example from checking the phone again).
Short-video use was also linked to more stress and anxiety. And what mattered most wasn't simply the minutes. It was compulsive, can't-stop use.
The caveat: most of these studies take a single snapshot in time, so they can't show cause. It's possible that people who already struggle with focus are drawn to short videos. Still, the pattern was consistent across many studies.
An experiment: what if mobile internet disappears for two weeks?
A 2025 experiment tested exactly this, and not on teenagers: the 467 participants were adults aged 18 to 74. They blocked all mobile internet on their phones for two weeks. They could still call and text, just no feeds, no browsing and no apps that need the internet. The results:
People's ability to sustain attention, measured with a computer task rather than self-report, improved by an amount similar to being about 10 years younger. Mental health and life satisfaction improved too. 91% of participants improved on at least one of these. Part of the reason was what they did with the freed-up time: more face-to-face socialising, more exercise and more time outdoors.
A myth worth busting
You may have heard that just having your phone on the desk, face down and silent, drains your brainpower. A 2024 analysis combining 33 studies (4,368 people) found no meaningful effect of the phone's mere presence. That's actually good news. The problem isn't the object. It's the interruptions and the habit of picking it up. When young people's phones were tracked, 97% used them during school hours, with a median of 43 minutes of use during the school day and, for some, more than six hours.
Why constant switching costs so much
Picture a typical evening of studying or working from home. You open your laptop, read a paragraph, check a message, watch "just one" video a friend sent, come back, reread the same paragraph, reply to a group chat, scroll for a minute because you're already on your phone… An hour later, the work that needed twenty focused minutes is still half done.
Every time you jump from a task to your phone and back, your brain has to "reload" what you were doing. Do that dozens of times an hour and you end up tired but with little done, often feeling scattered and slightly guilty. Over time, many people start to believe they are "just bad at concentrating," when in fact they rarely give their attention a real chance. The internet even has a slang name for that foggy feeling: "brain rot." It's a joke, but it describes a real experience: fast, constant input that leaves you feeling emptier rather than fuller.
Key numbers
- 2 weeks without mobile internet: adults' focus improved as much as if they were about 10 years younger. Castelo et al., 2025
- 9 in 10 of them got better in at least one way: focus, mood or how satisfied they felt with life. Castelo et al., 2025
What to take from this
Attention is one of the most valuable things you own, and it's what apps compete for. The research suggests your focus isn't "broken." It's trained, and what is trained can be retrained, at 16 or at 60. The two-week experiment shows how quickly the brain can respond when the constant stream of input stops.
Quick self-check
- Do you find it hard to watch a film or read for 20 minutes without checking your phone?
- Do you open short videos "for a minute" and lose much longer?
- Do you check your phone in the middle of tasks, even when nothing has buzzed?
- Do slower activities (lectures, books, long talks) feel more boring than they used to?
- Do you end a day feeling busy but scattered?
This is not a diagnosis. Several "yes" answers simply suggest your attention may be getting pulled more than you'd like.
Ongoing difficulty concentrating can have many causes, from stress and poor sleep to ADHD. If it's affecting your studies or work, it's worth discussing with a professional.
References
- Nguyen, L., Walters, J., Paul, S., Monreal Ijurco, S., Rainey, G. E., Parekh, N., Blair, G., & Darrah, M. (2025). Feeds, feelings, and focus: A systematic review and meta-analysis examining the cognitive and mental health correlates of short-form video use. Psychological Bulletin, 151(9), 1125–1146. doi:10.1037/bul0000498
- Castelo, N., Kushlev, K., Ward, A. F., Esterman, M., & Reiner, P. B. (2025). Blocking mobile internet on smartphones improves sustained attention, mental health, and subjective well-being. PNAS Nexus, 4(2), pgaf017. doi:10.1093/pnasnexus/pgaf017
- Hartanto, A., Lua, V. Y. Q., Kasturiratna, K. T. A. S., Koh, P. S., Tng, G. Y. Q., Kaur, M., Quek, F. Y. X., Chia, J. L., & Majeed, N. (2024). The effect of mere presence of smartphone on cognitive functions: A four-level meta-analysis. Technology, Mind, and Behavior, 5(1). doi:10.1037/tmb0000123
- Common Sense Media (2023). Constant Companion: A week in the life of a young person's smartphone use. commonsensemedia.org
About these sources
These 4 sources were published between 2023 and 2025. Reliability: 3 high, 1 medium. High means a review of many studies, a large experiment or long-term study, or official data checked in the original. Medium means useful evidence with real limits, such as a small sample, a single point in time, or no peer review. How we choose and check sources.
Educational guidance, not diagnosis or medical care.