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The Madness of Multitasking

More and more people are finally getting the message that multitasking is a bad idea. But few people are aware of the brain science that explains why this widespread practice can be a productivity disaster.

Whenever you shift from one activity to another, say, writing a presentation to checking your e-mail, your brain goes through a four-step process. It makes no difference how quickly you shift your attention; the process is essentially the same.

1) To begin with, blood rushes to the anterior prefrontal cortex, which notifies the rest of your brain that you’re about to work on your presentation.

2) This all-points bulletin to your brain has two parts. First it searches for the neurons that you’ll need for a particular task and then it notifies those neurons that they’re needed. The search and notification is fast, but it still takes a few tenths of a second.

3) Then, when you decide to stop writing your presentation and check your e-mail, your brain must first disengage from the current task before moving on to the next. Strictly speaking, what we typically refer to as multitasking isn’t really multitasking. You aren’t actually doing two things at once. What you’re doing is more accurately called rapid sequential task switching. But as you’ll see, it’s not nearly rapid enough.

4) The final step is the same as the first, only this time the anterior prefrontal cortex, instead of telling your brain that you plan to write your presentation, will notify it that you intend to check e-mail. Once again, a few tenths of a second are required.[I]

The whole process of shifting from one task to another takes about half a second. That might not seem like much until you realize that look this this process is repeated every single time you shift from one task to another. Those half seconds begin to add up quickly. What’s more, each time you shift, to some extent you’re starting over. If multitasking were advertised like a soft drink, its slogan would probably be, “Now where was I?”[II]

If you remain unimpressed with the prospect of wasting time in half-second increments and aren’t all that concerned about constantly having to reorient yourself, perhaps some additional statistics will make a stronger impression.

  • People who are interrupted take an estimated 50 percent longer to complete a task and have been found to make up to 50 percent more errors.[III]
  • Constantly texting or checking e-mailing – a mainstay of multitaskers – has been shown to reduce your IQ by as much as 15 points.[IV]

Granted, some interruptions are unavoidable. But the thing about multitasking is that it’s interruption by choice not by chance. Why would you knowingly reduce your efficiency, deliberately increase your odds of making mistakes, and intentionally make yourself less intelligent?

Maybe now that you’ve read this, you no longer will.

[I] Medina, John. Brain Rules. Seattle: Pear Press, 2008. pp. 86-87.
[II] Medina, 87.
[III] Medina, 87
[IV] Rock, David. Your Brain At Work, New York: Harper Collins, 2005., p. 36