Watching someone juggle makes us apprehensive. Each time they add an orange or a bowling ball, the risk of failure goes up. We wait, wide-eyed, knowing that one small slip could make the whole thing fall apart. After all, they only have two hands, and there’s no way to overcome that practical limit on tossing oranges or bowling balls. 

The same thing goes for our brains, at least when it comes to multitasking. No matter how well we think we do it, the practical limits of biology mean that all we’re really doing is slowing ourselves down—and increasing our odds of failure.

Just like a juggler only has two hands, our brains have “a very limited capacity for multiple simultaneous thoughts,” as one MIT study explains. In fact, our brains are built to keep multiple thoughts away from each other.

Essentially, your brain waves are the coordinated oscillations of the activity of millions of neurons (this image helps visual it). Those waves oscillate anywhere from once per second to more than 100 times per second, and the brain keeps multiple thoughts from interfering with each other by “juggling” them out of sync with one another. 

The cost of this complex organization system is that “only a few thoughts can fit in each brain wave,” as the MIT authors write.

Do something simple, like washing dishes and listening to a podcast, and you’ll probably be fine. But increase the complexity—say, read your emails while trying to pay attention in a meeting—and you aren’t very effective at all.

In fact, you’re not even multitasking. What you’re doing is task switching; jumping between two or more tasks at a rapid rate. It can feel seamless, especially since  the cost of switching can be less than a second. But add that up countless times over the day, and those brief mental gaps can cost as much as 40 percent of your productive time, according to the American Psychological Association.

And no, people that multitask a lot don’t simply get better at it. A study of hundreds of Stanford University students showed the opposite. Heavy multitaskers aren’t more efficient—they just proved to be much more distractible. 

So next time you catch yourself trying to multitask, think of your brain like the juggler’s two hands. It can only hold so many things at a time before, sooner or later, it drops the ball.

Image created with Dream Studio