When we attempt to multitask, we don’t actually do more than one activity at once, but quickly switch between them. And this switching is exhausting. It uses up oxygenated glucose in the brain, running down the same fuel that’s needed to focus on a task.
“That switching comes with a biological cost that ends up making us feel tired much more quickly than if we sustain attention on one thing,” says Daniel Levitin, professor of behavioural neuroscience at McGill University.
“People eat more, they take more caffeine. Often what you really need in that moment isn’t caffeine, but just a break. If you aren’t taking regular breaks every couple of hours, your brain won’t benefit from that extra cup of coffee.”
Studies have found that people who take 15-minute breaks every couple of hours end up being more productive, says Levitin. But these breaks must allow for mind-wandering, whether you’re walking, staring out the window, listening to music or reading.