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Is Multitasking Limited by a Mental Bottleneck?

Our ability to multitask is limited by the prefrontal cortex














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Next to the many amazing feats our brain pulls off daily, its inferior ability to juggle a few simple tasks sticks out like a sore thumb. Now research from Vanderbilt University suggests that these limits on multitasking arise from slow processing in the prefrontal cortex, the brain’s central executive. Although the area has been known to be involved in multitasking, its exact role is a matter of debate.

Using functional MRI, the researchers found that when people were juggling two assignments, their prefrontal cortex appeared to deal with the tasks one by one—creating that familiar mental bottleneck—instead of processing them in parallel as do sensory and motor parts of the brain. With training the prefrontal activation time became shorter, cranking up the speed of the mental conveyor belt by about 10 times. Unfor­tunately, the researchers note, the benefits of training might not apply to tasks other than those specifically practiced. “It’s not like you become able to multitask [with drills]; it’s just that you become able to do each task very quickly,” says cognitive neuroscientist Paul Dux, now at the University of Queensland in ­Australia, who conducted the experiment.


This article was originally published with the title Mental Bottleneck.



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  1. 1. mattnyc 09:46 AM 11/24/09

    This research is from 2006, isn't it? or has there been an update since then?

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  2. 2. eco-steve 09:57 AM 11/24/09

    The brain is very good at some multi-tasking. It processes the five usual senses simultaneously, not forgetting balance and the other overlooked functions such as breathing. Think of the multiple operations necessary for a tiger chasing prey through dense jungle! Try getting a robot to do that! When i was young I could follow multiple conversations around me, but now I am partially deaf. And women are very good at knitting whilst talking on the phone while supervising several children and making sure the milk doesn't boil over on the stove!

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  3. 3. kottke in reply to eco-steve 11:03 AM 11/24/09

    Yes, eco-steve, you are talking about sensory and motor channels multitasking. If you try to hold two conversations at the same time (both use the language channel), you leak efficiency.

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  4. 4. kottke 11:06 AM 11/24/09

    eco-steve, it reads like you are talking about sensory and motor channels multitasking. This is specified in the article. But when we try to engage in two conversations at the same time, for example, we cannot, because we only have one language channel with which to process. (Or we can, but each conversation is stilted and not entirely efficient.)

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  5. 5. harol 06:37 AM 11/27/09

    There are limits to everything, but that is begging the question. The time involved seems to me to be the time translating the vision logic of the whole brain into words. Isn't the conscious mind a million times slower than the whole brain? It's more a matter of not having an open mind that blocks ideas. They would come fast enough, except when there are contradictions or errors in our thinking, errors in our biology, except in some cases. A quarterback sees the playing field in slow motion after the ball is snapped and Michael Jordan is obviously 'in the zone' when he sees the other players in slow motion. All that seems to be treated in Emotional Intelligence in sports. Men can be quite intuitive, despite having ten percent less connections between the hemispheres of the brain. It's a matter of custom or training. Einstein said the, "The only real valuable thing is intuition." He pretty much meant just that. He said he wasn't a genius, but only used his intuition. Aristotle said that only by using intuition are we really thinking anything new. Maybe the article isn't attacking the brain as inadequate, but many people seem to want us to question our thinking so that they can do it for us.

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  6. 6. eco-steve 08:53 AM 12/2/09

    kottke : Just think about trained interpreters. They speak in one language whilst simultaneously interpreting another. That is, they are multitasking....
    Personally, I speak fluent English and French, but unlike translators I think in either one language or the other. This seems to suggest that the brain has seperate language areas, but translators can use several at once.

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  7. 7. Dream_writer 05:38 PM 5/27/10

    I don't speak any foreign languages, but I can read Latin straight into English without consciously translating it--a form of multitasking that the article implies is impossible. I think that different languages can be wired into different subsections of the language area of the brain and communication between them can happen without the intermediary of the prefrontal cortex, which is the cause of the mental bottleneck the article discusses. Of course, I'm just a layperson, but I would suggest that further research into this particular type of phenomenon (into which translators also fall, as discussed above) would be a valuable area of investigation for neuroscientists

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