Does the Multi-Tasking Brain Max Out at Two Tasks?

By Smriti Rao | April 16, 2010 2:18 pm

science-scanA team of French scientists have proposed that when it comes to multi-tasking, our brains can handle only so much. In a new study, published in Science, scientists Sylvain Charron and Etienne Koechlin found that while the brain can easily divide its attention between two tasks, a third task will begin to slow it down–suggesting there is an upper limit to our multi-tasking abilities.

The scientists asked volunteers to do two complicated matching tasks simultaneously. With two tasks to deal with, the brain’s frontal lobes swung into action, working together to get the job done. The left side of the brain picked up one assignment while the right managed the other. But when scientists threw a third task into the mix, the brain began to fumble, with the volunteers making mistakes and slowing down, leading Koechlin to suggest that our frontal lobes “can’t maintain more than two tasks.”

To find out more about how the brain maxes out on multi-tasking and what this means for people who drink coffee and text while driving, head to Not Exactly Rocket Science’s for Ed Yong’s post: When multi-tasking, each half of the brain focuses on different goals.

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Image: Etienne Koechlin

  • Mer-mer

    I pretty much only do one thing at one time, but with music almost always in the background–I like it that way. I find it keeps my head cleared and cuts down on the stress…

  • katesisco

    Agree Mer-mer. Had first seizure Nov 2009 , total surprise but explains me. Seems like brain trauma makes the brain hard to let go of consciousness, or maybe it is just old age. Delta sleep is hard to come by but without it, like Vit C, you die.

  • Mary Stack

    I really can’t multitask -except when I am doing something creative. In that case, I can completely zone out on another task and still manage an excellent piece of art.

  • Mind_UR_Brain

    Capacity for multi-tasking depends upon capacity of working memory. Working memory can be expanded with exercise, so capacity for multi-tasking is not an immutable characteristic.

  • m

    i am curious then, people focus on more than 1 task at a time when driving in traffic.

    how does something like that fit into their study?

  • perspective

    Driving is only high stress or complicated when you do it wrong. It’s not the coffee you’re drinking at the wheel, it’s the two cups you drank before you got behind it. If people would slow down and spread out, instead of fighting over imaginary real estate and racing, almost anyone could easily drive safely.

  • ryan

    that is just like saying, you can’t pat your head & rub your tummy while walking & chewing gum all at once.

  • Andrew

    @m – Almost everyone is an “expert” driver. Given the number of hours a day that Americans (in particular) spend driving, much of the process is subconcious and even then, adding another layer of complexity (talking to someone who is in the car with you, much less holding a phone or typing, also) significantly decreases your reaction time in case of an emergency.

    Granted, we have vast differences in protocol amongst all these “experts” but it there is no greater testament to the fact that we are all very good drivers than the fact that more people don’t die on two lane highways. You don’t think about it because you’ve been doing it all your life but two cars approaching each other at relative speeds of 130 mph (65 mph + 65 mph) is a really scary thing unless everyone who is doing it is really, really reliable.

    There are plenty of counter examples of people who make bad decisions on the road but they are if anything further proof of how good we have it that they can get away with that stuff on a regular basis. There would be a lot fewer accidents and deaths if they didn’t but if you want to see a bad driver, go volunteer to teach Driver’s Ed. They are bad because they don’t have the experience. The rest of the maniacs are just plain foolish.

  • m

    @ Andrew…

    then in the case of the study, it may be that the “two complicated tasks” will get easier to manage with time? Like driving, these tasks become sub-concious?

    I really dont know, but its an interesting article and does not mention what happens to the brain after repeating the complicated multitask tasks over and over.


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