# Does Your Phone Make You Dumber? Brain Rot and the Research on Cognition Source: https://iqcat.vercel.app/en/blog/smartphone-brain-rot-iq Published: 2026-09-04 Publisher: NekoIQ (https://iqcat.vercel.app) Tags: 認知能力, 心理学 > Brain rot, the 2024 word of the year, describes mental exhaustion from overconsuming low-quality online content. From the experiment in which a phone on the desk lowers working memory and fluid intelligence scores to a meta-analysis linking digital device use with less cognitive decline in older adults, here is what the research says. ## Key takeaways - Brain rot was the Oxford Word of the Year 2024 and refers to cognitive fatigue from overconsuming low-quality online content. It is not a medical diagnosis. - The brain drain effect, in which a smartphone merely within view lowers scores on working memory and fluid intelligence tasks, was reported in an experiment with more than 500 students. - In a meta-analysis of about 411,000 adults aged 50 and over, digital device use was associated with a lower risk of cognitive decline. There is no evidence that phones uniformly damage the brain. - A short-term drop in IQ, a relative position, and a drop in task performance caused by divided attention are different phenomena. Many people share the feeling that their phone has made them slower or that short videos have ruined their concentration. In 2024, brain rot was named the Oxford Word of the Year, and terms such as smartphone brain and digital dementia spread in Japan. This article sorts out what research sits behind those words, what is known, and what is not. ## What brain rot refers to According to a review by [Yousef and colleagues (2025)](https://doi.org/10.3390/brainsci15030283), brain rot refers to the cognitive decline and mental exhaustion experienced by adolescents and young adults from excessive exposure to low-quality online material, especially on social media. Reviewing studies from 2023 and 2024, the authors break the phenomenon into components such as divided attention, reward-system stimulation, and poorer sleep. Crucially, brain rot is not a medical diagnosis. What the research examines are states such as sustained attention, fatigue, and mood, not structural change in the brain. ## A phone on the desk is enough to lower scores The best-known experiment directly measuring how a smartphone affects cognitive test performance is the brain drain study by [Ward and colleagues (2017)](https://doi.org/10.1086/691462). More than 500 undergraduates were assigned to keep their phone on the desk, in a pocket or bag, or in another room while completing a working memory capacity task (OSpan) and a fluid intelligence task (a Raven-style matrix test). Scores were highest when the phone was in another room and lowest when it was on the desk. Even switched on but silent, a phone within view claimed part of the participants' attention, leaving fewer cognitive resources for the task. This is not a case of the phone lowering IQ; it is a case of task performance dropping because attention is divided. The effect is temporary and disappears when the phone is moved away, which is also why putting your phone in another room before an IQ test is rational (see [IQ test strategy](https://iqcat.vercel.app/en/blog/iq-test-strategy)). ## In older adults, the association runs the other way The claim that screens eat away at the brain does not fit large datasets on older adults. [Benge and Scullin (2025)](https://doi.org/10.1038/s41562-025-02159-9) meta-analyzed 57 studies covering about 411,000 people aged 50 and over and found that those who used digital devices tended to have a lower risk of cognitive decline and impairment. This is a pooled result from observational studies, so reverse causation is possible: people whose cognition is already stronger may simply use devices more. Even so, the uniform harm implied by the phrase digital dementia is not supported, at least in data on middle-aged and older adults. ## Does IQ drop? Separate relative position from task performance It helps to distinguish IQ from performance on the task in front of you. IQ is a relative position within a same-age population and does not move much with short-term habits (see [Does IQ change with age?](https://iqcat.vercel.app/en/blog/iq-and-age)). Divided attention, sleep loss, and fatigue, on the other hand, reliably lower your score on the day. What phone overuse mostly produces is the latter. Abilities that depend on the day's condition, such as processing speed and working memory (see [What is processing speed?](https://iqcat.vercel.app/en/blog/processing-speed-training)), fall and test scores fall with them. But that is the kind of decline that comes back after you put the phone away and rest. On long-term effects, definitive data are still lacking. Research on how prolonged passive viewing shapes attentional habits in young people is ongoing, and no firm conclusion has been reached in either direction. ## In practice: three habits that protect attention The measures that follow directly from the research are surprisingly simple. - When you need to concentrate, put the phone in another room or out of sight - Separate passive scrolling from purposeful use (looking things up, messaging, studying) and track the former - Set fixed times to check notifications in batches and cut interruptions How delegating thinking to AI affects memory and ownership is covered separately in [Does relying on AI make you dumber?](https://iqcat.vercel.app/en/blog/ai-cognitive-debt). ## Put the phone in another room and measure your real ability To learn where your reasoning stands, the first step is to measure it under conditions where attention is not divided. The [free NekoIQ IQ test](https://iqcat.vercel.app/en/start) scores 20 questions across spatial reasoning, pattern recognition, logical reasoning, and classification (about 10 minutes) with item response theory and reports an estimated IQ, deviation score, and top percentage. Move your phone off the desk before starting and you can test this article's claims yourself. The numbers are estimates, not the results of a formal psychological assessment. ## Frequently asked questions ### What is brain rot? A term for the dulling of concentration and thinking caused by overconsuming low-quality online content, especially on social media. It was the Oxford Word of the Year 2024. It is not a medical diagnosis; research treats it as a matter of attention and fatigue. ### Does using a smartphone lower your IQ? There is no evidence that IQ itself drops. Experiments do show that a smartphone merely within view lowers scores on working memory and fluid intelligence tasks, because part of your attention goes to the phone. Leaving it in another room restores performance. ### Does digital device use raise the risk of dementia in older adults? A 2025 meta-analysis reports the opposite association. In data on about 411,000 adults aged 50 and over, people who used digital devices tended to have a lower risk of cognitive decline. Causation is unsettled, but the result does not support the idea of digital dementia. ## Disclaimer NekoIQ provides estimates for entertainment and self-understanding. It is not a medical, clinical, or official psychological assessment. Percentages are derived from a normal distribution with mean 100 and SD 15.