Your phone doesn't have to buzz to cost you something. That's the claim, anyway.

You know the setup. Deep in a refactor, five files open, a call chain held in your head like a stack of plates. The phone is face-down next to the keyboard, on silent. You're not touching it. You're barely aware of it.

In 2017 a team of researchers said that phone was still taking a cut of your brain. The headline went everywhere: the mere presence of your smartphone reduces brain power.

Then other labs tried to repeat it. What happened next is a better lesson than the original finding.

The brain drain experiment

Adrian Ward at the University of Texas at Austin, with Kristen Duke, Ayelet Gneezy and Maarten Bos, ran two experiments with close to 800 smartphone users. The paper was published in the Journal of the Association for Consumer Research.

The setup was simple. Before a set of hard tests, people were randomly told to put their phone in one of three places:

  • on the desk, face down
  • in a pocket or bag
  • in another room

Everyone set their phone to silent. Then they did tasks that strain working memory, the small mental workbench where you hold and juggle information right now. One was the operation span task: solve maths problems while remembering a sequence of letters. Another was Raven's matrices, a classic puzzle test of fluid reasoning.

The result: people whose phones were in another room did better than people whose phones sat on the desk. The pocket-or-bag group landed in between. In the second experiment it didn't matter whether the phone was on or off. And the people who said they depended most on their phones showed the biggest drop.

Ward's explanation was neat. Not thinking about something takes work. "The process of requiring yourself to not think about something uses up some of your limited cognitive resources," he told UT News. "It's a brain drain."

A head in profile with a small workbench of four glowing slots, one taken up by a phone while code waits outside

If you write code, that idea lands hard. Working memory is the whole game. It's where you keep the variable names, the state of the bug, the three things the function has to do before it returns. Most researchers think it holds only a handful of items at once. Lose one slot to a background process and you feel it.

So should every developer lock their phone in a drawer in the next room?

Then the replications came in

Here's the part that rarely made the headlines.

In 2022, Ana Ruiz Pardo and John Paul Minda at Western University ran a pre-registered direct replication of Ward's second experiment. Same six conditions (desk, bag, other room, phone on or off), same operation span task. They recruited 453 students and analysed 383 after exclusions.

No effect. Phone location made no difference to working memory scores.

A Swiss team led by Matthias Hartmann had already tested short-term and prospective memory with the phone on the desk or away from it, in Consciousness and Cognition in 2020. No overall effect there either.

Then came the meta-analyses, which pool many studies together:

  • Douglas Parry (Stellenbosch University) combined 56 effects from about 7,000 people in Media Psychology. Only one of six pooled effects was significant: a small hit to working memory. He called it "smaller than theorized" and flagged poor statistical power across the field.
  • Andree Hartanto and colleagues analysed 166 effect sizes from 33 studies and 4,368 people in Technology, Mind, and Behavior. Their pooled effect was d = −0.02. Basically zero. Smartphone dependency didn't change it.
  • Böttger, Poschik and Zierer at the University of Augsburg pooled 22 studies of smartphone presence and use in Behavioral Sciences and found a small negative effect overall, clearest for memory.

So the honest answer is: if a silent phone on the desk costs you anything, it's probably small. Much smaller than "your phone makes you dumber" suggests.

A row of identical lab desks: a phone on the first, a phone in a bag on the second, and empty desks near a closed door

The notification is the real thief

That doesn't let the phone off the hook. It shifts where the cost lives.

In 2015 Cary Stothart, Ainsley Mitchum and Courtney Yehnert at Florida State University gave people a dull but demanding task: numbers flash about once a second, press a key for every one except 3. Two blocks of 360 trials. During the second block, some people's phones got four calls or four texts.

Nobody answered. Nobody looked. They just heard or felt the alert.

Errors went up anyway, more than in the group that got no notifications. The researchers suspect the alerts set off task-irrelevant thoughts (who was that?) that kept running after the buzz stopped. They noted the size of the effect was similar to costs seen in studies of distracted driving. One caveat they flagged themselves: the text group started with fewer errors, so that half of the result is less certain than the calls half.

Put the studies side by side and a pattern shows up. A silent object sitting there: weak, disputed evidence. A ping that pulls your mind out of the task, even for a second: much clearer.

For a developer, that's the difference between a phone on the desk and a Slack badge blinking in the corner of your IDE.

What you can try today

You don't need to exile your phone to another room. Try this instead:

  1. Kill the sounds and vibration, not just the screen. Face-down does nothing if it still buzzes. Use Focus or Do Not Disturb for your deep-work block.
  2. Batch your checking. Pick a time, like the end of each Pomodoro or after a commit, and look at everything at once.
  3. Run a tiny experiment on yourself. Do one morning with the phone on the desk and one with it in a drawer. Note how often you thought about it. If the answer is "a lot", Ward's dependency finding may apply to you, and the drawer is cheap.
  4. Park the open loop. Before you break focus, write one line about where you were: "next: check why the token refresh runs twice." It gives your working memory permission to let go.

Where this fits in how I learn

Working memory is tiny and easy to knock over. That's exactly why I don't trust it to hold what I learn from talks, docs and threads either. I built Recl to deal with that: I save a video or article, it pulls out the key takeaways, and later it brings them back as quick recall questions so the good stuff actually sticks.

A saved video in Recl showing its summary and numbered key takeaways

The phone is probably not quietly draining your brain. The buzz is. Turn that off, and give your workbench back to the code.

Asutosh writes about memory and how brains learn, and builds Recl, an app for remembering what you watch and read.

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