Multitasking: why doing several things at once makes you slower

It's the scene of any business owner on a Tuesday at eleven in the morning: with one hand you reply to a message, with the other you look up a figure for an invoice, and meanwhile the phone rings. You feel like an efficiency machine, capable of everything at once. The uncomfortable truth is that your brain isn't doing several things at once; it's leaping between them at high speed, and every leap costs you.

What we call 'multitasking' is, almost always, rapid task-switching, and research has shown for decades that this constant switching makes us slower and more prone to errors. It's worth understanding why, because the problem isn't willpower: it's how the mind works.

Your brain doesn't do two things, it switches

When you think you're doing two tasks at once, you're actually turning one off and the other on, over and over. Researchers at the American Psychological Association, led by David Meyer, described this process in two steps: first a 'goal shift' (I want to do this instead of that) and then a 'rule activation' (I turn off the rules for the old task and turn on the rules for the new one).

Each of those steps takes a fraction of a second. It seems like nothing. But when you switch dozens of times an hour, those fractions add up. And there's a key detail: the brain takes longer to return to a complex task than to a simple one, so the harder the thing you left half-done, the more each interruption costs you.

Even brief mental blocks created by shifting between tasks can cost as much as 40 percent of someone's productive time.

The cost of switching, in numbers

That 40 percent figure, attributed to researcher David Meyer, is the one that should make you stop. It's not that you lose a bit of efficiency: it's that nearly half your useful time can vanish in the friction of switching from one thing to another. And there's a second, less visible cost:

• It takes you longer to finish each task than if you did them one at a time.
• You make more errors when switching than when focusing on a single thing.
• The cost is higher when the tasks are complex or unfamiliar.
• You end the day exhausted, with the feeling of not having finished anything fully.

Those who multitask most are the worst at it

Here comes the most counterintuitive finding. In 2009, researchers Eyal Ophir, Clifford Nass, and Anthony Wagner of Stanford University studied 262 students. They expected to uncover the superpower of those who live doing a thousand things at once. They found the opposite.

The people who multitasked the most turned out to be the worst at filtering irrelevant information, the worst at holding things in memory, and, most surprisingly, the worst at switching tasks, the very skill multitasking supposedly trains. Those who rarely multitask outperformed the chronic multitaskers on every measure of mental control.

The people who multitask the most are, demonstrably, the worst at it.

What to do in a business where everything shouts at once

Saying 'do one thing at a time' is easy; living it in a business where the customer, the supplier, and the bank all message you at the same time is another matter. But there are realistic ways to cut the switching:

• Batch similar tasks: answer all your messages together in blocks, not one by one all day.
• Turn off notifications while doing something that demands focus, like balancing the books.
• Reserve interruption-free slots for what's important, even if it's just 30 minutes.
• Delegate or automate the repetitive, so it doesn't pull your attention every five minutes.

This is exactly where automating customer service helps. If an assistant like Lidia replies and books on WhatsApp for you, you stop jumping to the phone every time a message lands and you recover blocks of focus for the work that really needs your head.

There's another silent enemy: guilt. Many owners feel that turning off the phone for an hour is irresponsible, that a customer might write. But flip it around: serving people half-distracted and making mistakes is worse service than serving them with focus a little later. Protecting your concentration isn't selfish, it's what lets you do your job well.

Takeaway

Multitasking is an expensive illusion: you feel like you're advancing on everything and you're actually stalling on everything. Your brain pays a toll every time it leaps, and that toll can take up to 40 percent of your useful time. Doing one thing at a time isn't going slower; it's the fastest way to finish well. Batch, kill the noise, and protect your focus like the scarce resource it is.

Sources

• American Psychological Association — https://www.apa.org/topics/research/multitasking
• Stanford University (Ophir, Nass, Wagner, 2009) — https://news.stanford.edu/2009/08/24/multitask-research-study-082409/
• Psychology Today — https://www.psychologytoday.com/us/blog/brain-wise/201209/the-true-cost-of-multi-tasking