Phones, Notifications and the Cost of Switching Tasks

Forty-seven seconds. That is roughly how long people in Gloria Mark's recent studies kept their attention on a single screen before switching to something else. Mark, a professor of informatics at the University of California, Irvine, has been timing office workers at their computers since the early 2000s, and in her 2023 book Attention Span she reports that the average had fallen from about two and a half minutes in 2004 to well under a minute in more recent measurements. The numbers come from small samples of knowledge workers, so they are not a portrait of everyone. The direction is hard to ignore, though, and a large share of those switches start with a phone or a notification.

What a switch actually costs

Psychologists have studied task switching in the lab for decades, and the basic finding is consistent: changing from one task to another takes time, even when both tasks are simple. In a 2001 paper in the Journal of Experimental Psychology, Joshua Rubinstein, David Meyer and Jeffrey Evans measured how long people needed to switch between tasks such as solving math problems and classifying shapes. Each switch added time, and the cost grew as the tasks became more complex or less familiar. The individual delay is a fraction of a second, but a morning with hundreds of switches adds up, and errors tend to rise along with it.

The cost does not end when you switch back. The organizational researcher Sophie Leroy named the effect "attention residue" in a 2009 paper: when people moved to a new task while the previous one was unfinished, part of their thinking stayed on the old task, and they performed worse on the new one. Anyone who has read the same paragraph three times after glancing at a message has felt this.

Interruptions also change how people work. In a 2008 study, Mark and her colleagues found that interrupted workers often finished tasks in about the same time as uninterrupted ones, but they did so by working faster and reported more stress, frustration and effort. Speed is not the only price. A figure that circulates widely says it takes about 23 minutes to get back to a task after an interruption; it comes from Mark's observational research on how long people took to return to an interrupted project, often after doing other things in between, and it is better read as a description of typical workdays than as a fixed recovery time for every ping.

"Multitasking" on complex work is mostly rapid switching. People can walk and talk at once, but two tasks that both need language or careful reasoning, such as writing an essay and following a group chat, compete for the same mental resources.

The phone on the desk

One study took the argument further. In 2017, Adrian Ward and colleagues published a paper in the Journal of the Association for Consumer Research with the memorable label "brain drain." Participants did tests of working memory and problem solving with their phone either on the desk face down, in a pocket or bag, or in another room. The phones were silenced. Those whose phones were in another room scored best, and the researchers concluded that the mere presence of a person's own smartphone took up some of their limited attention, even when they were not using it.

The study received enormous attention, and it should be held more loosely than its headlines suggest. Several later replication attempts, including larger and preregistered ones, did not find the same effect on test scores or found it much smaller. The current honest summary is that the phone-in-another-room idea is plausible and low cost to try, but the evidence that a silent phone on the table drains your performance is mixed rather than settled.

What is not in dispute is that a phone which lights up and buzzes causes interruptions, and each interruption triggers the switching costs described above. Reducing how often the phone asks for attention is the part with the firmest support.

Setting up the phone and the hour

Both major phone systems now include tools for this, and a few minutes in the settings menu does more than willpower alone. The most useful are:

• Focus modes. On iPhone, Focus (under Settings) lets you choose which people and apps can reach you during set hours or at a set place. Android phones offer Do Not Disturb with exceptions, and many include a separate Focus mode in Digital Wellbeing that pauses chosen apps.
• Notification summaries. iPhones can hold non-urgent notifications and deliver them in a batch at times you pick. Several Android phones offer similar scheduling or let you silence whole categories of notifications.
• Grayscale. Turning the screen black and white makes colorful app icons and feeds less appealing. On iPhone it is under Accessibility color filters; on Android it is often in Digital Wellbeing's bedtime settings or the accessibility menu.
• App limits. Screen Time on iPhone and app timers in Android's Digital Wellbeing cap daily minutes for specific apps and lock them when time runs out.

Time structure helps too. The Pomodoro technique, developed by Francesco Cirillo in the late 1980s and named after the tomato-shaped kitchen timer he used as a student, breaks work into 25-minute stretches separated by short breaks, with a longer break after four rounds. Its value is less in the exact numbers than in turning "check the phone whenever" into "check the phone at the break." Formal research on the method itself is limited, and some people find longer blocks suit deep work better, so adjust the timer once the habit holds.

For a concrete first step, open your notification settings tonight and turn off alerts for every app that is not a person trying to reach you or something time-sensitive, such as a bank fraud alert or a calendar reminder. Android can sort that list by the most frequent senders, and Screen Time on iPhone shows notification counts per app, so start with whichever app tops the count.