Single tasking vs multitasking comes down to switching costs. When you juggle tasks, you're usually switching between them, and lab studies found that every switch costs time, more so for complex or unfamiliar work. For anything that needs real thought, doing one thing at a time is usually the faster, calmer choice.
Single tasking means giving one task your full attention until you finish it or reach a natural stopping point. Multitasking usually means trying to handle two or more tasks in the same stretch of time, like answering email during a call or texting while you write a report.
For most thinking tasks, doing two things at once is really fast switching. The American Psychological Association describes research by David Meyer, Jeffrey Evans and Joshua Rubinstein suggesting that the brain's executive control works in two stages: goal shifting ("I want to do this now instead of that") and rule activation ("I'm turning off the rules for that and turning on the rules for this"). Every switch runs through both.
The APA describes four experiments in which young adults switched between different tasks. The results were consistent:
People lost time when they switched, for all the tasks tested.
The more complex the tasks, the more time people lost.
Switching to unfamiliar tasks cost more. People got up to speed faster with tasks they knew well.
Each delay is small, but they add up. Meyer has said that even brief mental blocks created by shifting between tasks can cost as much as 40 percent of someone's productive time. As the APA puts it, multitasking may seem efficient on the surface but may actually take more time in the end and involve more error.
There's a stress cost too. Attention researcher Gloria Mark, of the University of California, Irvine, said on an APA podcast that decades of lab research show that when people multitask, they experience stress and their blood pressure rises.
Media multitasking means using several streams of media at once, like scrolling your phone while a show plays and a laptop sits open.
A well-known 2009 Stanford study compared heavy and light media multitaskers. The heavy multitaskers were more easily distracted by irrelevant things around them and by irrelevant information in memory. Surprisingly, they also did worse on a test of task-switching ability, likely because they found it harder to filter out the task they weren't doing.
The picture since then is more mixed. A 2018 review by researchers at UC San Francisco and Stanford found that the balance of evidence suggests heavier media multitaskers perform worse in several areas of thinking, often on tasks that depend on sustained attention. But many studies find no difference between groups, and researchers still don't know which way cause and effect runs. It could be that heavy media multitasking weakens focus, or that people who already find it harder to focus multitask more.
Pick one task and name its first step. "Draft the three main points," not "work on the presentation."
Close what you don't need. Shut extra tabs, email and chat for this block.
Move your phone. Put it in a drawer or another room, or silence notifications for the session.
Set a time box. Try 25 minutes to start and lengthen it as single tasking gets easier. Our sister site's guide to the Pomodoro Technique explains one popular way to do this.
Keep a parking list. When a stray thought pops up, like "reply to Sam," jot it down and go back to the task.
Stop at a natural break. Mark said that interrupting yourself in the middle of something, rather than at a natural stopping point, takes more mental effort and is more stressful. Finish the paragraph or step first.
Some work comes in lots of small pieces: emails, messages, invoices, quick calls. Batching means grouping similar small tasks and doing them together at set times, instead of handling each one the moment it arrives.
Email is the classic example. Mark said her research finds people check email on average 77 times a day. Checking at a few set times instead cuts out dozens of switches.
Example batching schedule (an example only, so adjust it to your job):
9:00 to 9:20: email and messages
9:20 to 11:00: one focused task
11:00 to 11:15: email and messages
1:00 to 1:30: calls and quick admin
4:00 to 4:20: email and messages, then plan tomorrow
If your job allows it, tell people when you check messages so they know when to expect a reply. For a fuller approach, see our sister site's guide to time blocking.
Single tasking matters most for complex, unfamiliar or important work. The APA findings suggest switching costs less between simple tasks you know well, so folding laundry while chatting with a friend isn't something to worry about. The big exception is anything where a split second matters. The APA notes that losing just half a second to task switching can make a life-or-death difference for a driver on a cell phone.
If trouble focusing affects your work, relationships or daily life even after you've cut back on switching, talk to a doctor or a mental health professional.
Researchers don't know whether it causes lasting changes. What's clear is that switching costs time in the moment, and some studies link heavy media multitasking with weaker performance on attention tasks, though many find no difference.
For complex work, usually yes. Every switch costs time, and the cost grows with harder and less familiar tasks.
For two tasks that both need real thought, what feels like multitasking is mostly switching back and forth, with a small cost each time. Simple, familiar tasks are easier to combine.
Using several media streams at the same time, such as texting while watching a show with a laptop open. Researchers study it to see whether heavy use relates to attention.
If you want a timer for single-task blocks, Attention Age: Focus Test includes a focus timer with free 10- and 25-minute sessions (45- and 90-minute sessions are in Pro), plus a Lock Screen Live Activity and optional ambient sounds. It also has a five-minute attention test with a weekly re-test, presented as entertainment and self-practice, not a medical or diagnostic test. No account is needed, results stay on your iPhone and there are no ads.
Get Attention Age free on the App Store
Multitasking: Switching costs (American Psychological Association)
Minds and brains of media multitaskers: Current findings and future directions (PNAS, via PubMed)
Why our attention spans are shrinking, with Gloria Mark, PhD (APA Speaking of Psychology)