The Brain Drain Study: Does a Nearby Phone Cost You Focus?

Your phone is face down on the desk, on silent, and you're not touching it. Can it still take something from your thinking? Four researchers tested that idea in 2017 and gave it a name that stuck: brain drain.

What the researchers did

The study, by Adrian Ward, Kristen Duke, Ayelet Gneezy and Maarten Bos, was published in the Journal of the Association for Consumer Research. Its starting point was a simple hypothesis: if part of your mind is busy keeping your phone at bay, less of it is free for anything else.

Across two experiments, nearly 800 smartphone users came to the lab and were told where to leave their phone, set to silent:

• On the desk, face down, in sight.
• In a pocket or bag, nearby but out of sight.
• In another room.

They then sat at a computer and took tests that needed their full concentration. The tests measured how much mental capacity they had available: working memory, the ability to hold and juggle information, and fluid intelligence, the ability to solve problems they hadn't seen before. In the second experiment the researchers also varied whether the phone was on or off. They also asked people how dependent they felt on their phones.

What they found

• Another room was best. People whose phone was in another room significantly outperformed those whose phone was on the desk, and slightly outperformed those whose phone was in a pocket or bag.
• Off wasn't enough. It made no difference whether the phone was turned on or off, or whether it lay face up or face down on the desk. What mattered was where it was.
• The most attached paid the most. People who were most dependent on their phones did worse than less dependent people, but only when the phone was on the desk or in their pocket or bag.
• Not a distraction in the usual sense. The cost appeared even when people succeeded at keeping their attention on the task and resisted checking their phones. The authors' reading: holding the phone at bay uses up some of a limited pool of mental resources, leaving less for everything else.

What the study can't tell you

Whether it holds up. This is the big one. In 2022, two researchers ran a preregistered replication that used the same tasks and conditions as the second experiment. They found no difference between the phone on the desk, in a pocket or bag, or outside the room. A 2023 meta-analysis of 22 studies did find an overall negative effect of phones, used or merely present, on memory, attention and general cognitive performance, but the effects varied widely from study to study and between kinds of thinking. A small German experiment the same year found lower attention scores among 42 students whose phone lay switched off on the desk than among those whose phone was outside the room. The fair summary is that the effect may be real but smaller and less reliable than the original headline.

How it plays out in daily life. These were laboratory tests of working memory and reasoning, not a day of work, study or conversation.

Who it applies to. The volunteers were smartphone users tested in a lab. The finding that the most dependent paid the most suggests the cost, if there is one, isn't the same for everyone.

What it means for your phone

Even if the brain drain is smaller than first reported, the remedy costs nothing:

• For work that matters, put the phone in another room, not just face down. In the original study every phone was on silent, and turning it off made no difference; distance did.
• If you feel lost without your phone, distance may matter more. The heaviest cost fell on the people most dependent on their phones.
• Make the walk part of the plan. When getting your phone back means leaving the room, checking it becomes a decision instead of a reflex.

If leaving the room isn't practical, a phone-free session in Unrotten is the next best thing: from Home's + button, a Work, Focus or Reading session locks the apps you chose until it ends, with a countdown on your Lock Screen. For a device built entirely around putting distance between you and your apps, read our Brick review, and for the wider research on focus, our guide to attention span.