"...In a 2005 Australian study published in the British Medical Journal, researchers interviewed, during a 27-month period, 456 hospitalized cell phone users who had each been involved in a crash. The scientists combed the drivers' call records to see how cell phone use affected their driving.

Whether they talked hands-free or with a phone clasped to their ear, the result was the same: During calls, and for 10 minutes after their completion, a driver's likelihood of crashing shot up fourfold."

Thought leadership' is no fan of multi-tasking, as regular readers will have ascertained. The Business Daily last week ran a piece summarising various international studies on the use of mobile devices while driving. The results were unsurprising. Scientists warn against distractions when driving.

The limiting factor, by the way, is not the number of hands available for driving: it's a driver's attention and processing capacity.

A lab study showed powerfully how doing two seemingly simple tasks can overload the brain and cause errors.

When the task of listening to a few sentences was added to driving, the results were shocking. Drivers listening to the sentences veered off the road almost 50 per cent more often than those allowed to focus uniquely on driving. There are limits to the brain's multi-tasking capacity.

It should be obvious to us in our daily lives, but it's not: we can't do more than one thing at a time, if we want to do it well. This is not limited to driving, where multi-tasking can cause death or permanent injury.

Juggling too many things is career-limiting in the work place. And yet the modern manager takes great pride in doing many, many things at the same time.

There is a terrible misconception about management: that the higher you go, the more things you are expected to handle at the same time.

Arrant nonsense. Whatever you have done well in your life, you have done by concentrating all your efforts on it.

Worst thing you ever did

That report you wrote while replying to 50 e-mails and holding 25 cell phone conversations and meeting 10 colleagues was probably the worst thing you ever did. If you are a senior manager wondering why you don't achieve more every day, look no further than your daily work patterns.

If you do not allocate time for specific tasks, and try to achieve a dozen things by throwing them all up into the air - then, well, you will soon be marked out as an under-achiever.

The most productive managers I know reserve a time of day for making calls, and another for e-mails and correspondence.

When they are in meetings, they do not sit fiddling with their phones under the table, pretending to listen. They keep a time of the day free for just thinking. They do not get sucked into obeying other people's silly deadlines. Yet, they deliver.

"Concentrate all your thoughts on the task at hand. The sun's rays do not burn until brought to a focus", said Alexander Graham Bell. The great achievers throughout the ages have always known this. It's time you did, too.