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Attention multi-taskers: Your brain can only handle so much Add to ...

The fence guy calls back while I'm making dinner. One backyard option is more affordable. The other is more durable. I'm trying to imagine which one might look better when I realize the mushrooms should have gone in before the garlic. And I forgot that my five-year-old asked for more juice. It was apple juice, right?

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Keeping track of these different bits of information requires what is referred to as "working memory." It is an ability that is critical for holding information in mind as we compare options, make decisions and switch between tasks. The challenge of these activities is that the brain can juggle only so much before losing something.

Maintaining information over short periods of time requires elevated and sustained neural firing in regions associated with working memory. Animal and human neuroimaging research suggests that the prefrontal cortex plays a critical role in this process. It also works with regions of the parietal lobes to help to prevent interference, or "cross-talk," from other competing brain signals.

And as a situation unfolds, help is needed to ensure that the information in working memory is appropriately updated. A growing number of studies suggest that the caudate nucleus, part of the basal ganglia near the centre of each hemisphere, is involved in this. Switching from one task to another also engages such working-memory regions as we bring to mind whatever information becomes newly relevant.

These processes are part of what are generally referred to as the brain's "executive" functions. They are given this lofty title because of their importance in allowing us to act strategically and to exert control over our thoughts, feelings and actions, according to the priorities we set for ourselves.

A decline in the brain's executive functions supporting working memory can have serious consequences, from momentary lapses in concentration and absent-mindedness, to failures to respond in appropriate ways to changing situations. Indeed, the link between working-memory ability and general cognitive performance is so strong that many researchers seriously consider working-memory capacity to be the very root of fluid intelligence.

This may explain why researchers have focused extensively on finding ways to train and strengthen an individual's working-memory ability. And while much more research is needed, the initial results are promising. A few weeks of daily practice with a computer-based task, requiring information to be held in mind while updating it or comparing it to newly presented information, has been shown to result in improvements not only on the working-memory performance, but also on other measures of reasoning.

Such training also appears to aid concentration, even for those with attention disorders. To bounce back from a distraction - a colleague stopping by to say hi or a phone call from your kid - you have to be able to keep track of what you were doing before you were interrupted. Difficulty switching back, bringing back to mind the critical bits of information for the task you were doing, is one of the main drawbacks to trying to multitask. And the consequences can be deadly.

For example, studies of pilot errors in fatal airline crashes indicate that problems are rarely due to the pilot not knowing what to do or when to do it, but more often due to failures in resuming a task after being interrupted, even by something as inevitable as a trip to the washroom. Problems recovering from interruptions are also known to increase with age.

So give your capacity-limited brain a break. Leaving the fence-buying for later may avoid any dinner-making, kid-watching disasters. Writing down what still needs to be done before switching to something new can help too.



Mark Fenske, co-author of The Winner's Brain: 8 Strategies Great Minds Use to Achieve Success , is an associate professor in neuroscience at the University of Guelph.

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