If I had the ability to watch every reader as she or he reads this piece, the odds are I would only have to wait a few minutes before someone spilled a cup of coffee while trying to text message and read this article at the same time.

Multitasking claims another victim!

After listening to one person after another explain to me how easy it is for them to carry on a conversation and text at the same time, or otherwise perform an endless number of tasks simultaneously, I finally came up with a way to politely explain that this is hogwash.

Here’s how you, too, can demonstrate the basic limitations of human concentration: Give them three balls.

If you don’t have a lot of balls around the office, you can also use apples, oranges, lemons or even candy bars.

Now ask the person to juggle these four items for at least 20 seconds without dropping one.

“But,” they may protest, “I don’t know how to juggle.”

Fortunately, juggling is easy to explain. You toss one ball in the air from your right hand, so that it reaches a peak and then falls into your left hand. When the first ball reaches its peak, you toss a ball from your left hand in the opposite manner. When that second ball reaches its peak, you toss the third ball, which also was in your right hand.

The hard part is not how to juggle but rather the concentration necessary to throw each ball at the right time with the right arc, and to catch each ball as it descends.

If you wish, you can allow the other person to go home and practice. Those who relish a challenge may come back and show you that—voila! —they can juggle.

Congratulate them, for they have now learned how to do one task effectively.

Now give them a fourth ball. Invite them to, once again, take all the time they need to practice. If the person comes back and demonstrates they can now juggle four balls, you now know one person who can multitask.

Yes, juggling four balls is like doing two things at once. This is the level of concentration required to do two things well, simultaneously.

Don’t be surprised if no one comes back a second time. The late Stanford professor Cliff Nass studied multitasking, and in 2009 Nass described how he and his colleagues were looking for multitasking activities at which multitaskers excelled.

In an interview with the PBS program, Frontline, Nass said, “We all bet high multitaskers were going to be stars at something. We were absolutely shocked. We all lost our bets. It turns out multitaskers are terrible at every aspect of multitasking. They’re terrible at ignoring irrelevant information, they’re terrible at keeping information in their head nicely and neatly organized, and they’re terrible at switching from one task to another.”

Translation: if you think you can multitask, you are delusional.


Need assistance with Bruce Kasanoff’s multitasking test—specifically, to help your colleagues (or yourself) learn how to juggle? Watch the video above and begin your own multitasking experiment.


Editor’s note: The original version of this article appeared on LinkedIn on Dec. 10, 2014.