Here's something about this column that you don't know. While I am writing these words, I am also answering my e-mail, juggling phone messages, cooking a six-course organic dinner, balancing my checkbook and playing Scrabulous with a 12-year-old podiatry student in Dubrovnik.

Yes, reader, I am a multitasker and proud of it. Or, I was proud until I picked up a new —and refreshingly tiny — book by Dave Crenshaw, “The Myth of Multitasking.”

Crenshaw, a Utah-based business coach, insists that we don't improve our effectiveness by doing two or three or 10 things at once. Instead, he suggests, we actually become less productive, driving our co-workers and our family moo-moo-goo-goo in the process.

Multitasking is a myth, Crenshaw writes, because the human brain simply cannot perform two tasks at once. David E. Meyer, Ph.D., of the University of Michigan agrees: “We will never, ever be able to overcome the inherent limitations in the brain for processing information during multitasking. It just can't be, any more than the best of all humans will ever be able to run a one-minute mile.”

I would argue with Meyer in terms of the one-minute mile. Obviously, he has never timed the race in your office when it is announced that scraps from the lunch meeting are available in the break room. But no one can disagree when it comes to the limits of the human brain. Spend five minutes with your manager and those limitations are as clear as a bell, if not an entire carillon.

Instead of multitasking, what we poor humans actually do is “task-switching.” Unable to walk and chew gum at the same time, we alternate between walking and chewing — a time-consuming, inefficient waste of brain power for which we pay a price; a price that time management types call the “switching cost.”

You can measure switching costs in minutes or in dollars; however, Crenshaw's argument is that when you go from e-mail to voice mail to snail mail and back again, you are not multiplying your productivity, but dividing it — less a significant discount for the time it takes you to crunch those rusty gears.

“Studies have shown that on average each person loses about 28 percent of the workday due to interruptions and inefficiencies,” Crenshaw writes. “Multitasking — or switch-tasking — is probably the biggest culprit.”

In the example that takes up most of the book, the multitasker actually wastes so much time in going back and forth between tasks that every “productive” hour is only 32 minutes long.

I know! Your management would be delighted if they got 32 minutes of work every hour, but don't give in to their outlandish demands. What you bring to the company is your sense of style and your infectious charm. Anyone can do work, only a very special employee can be a celebrity icon.

Another destructive aspect of the multitasking myth is the idea that you can allow yourself to be interrupted all through the day and still remain a productive employee. Having assorted managers, co-workers and flunkies bop in and out of your life on e-mail, voice mail, Twitter and Blackberry may give the impression that you are in the mix and the flow, but the need to deal with all these humans and their various demands will inevitably take its toll on your mission-critical tasks: playing online poker and keeping up with the juicy celebrity news on Perez Hilton.

Crenshaw's answer is to set certain times when you will accept visitors or return telephone calls.

“There is an illusion that many people buy into,” Crenshaw writes, describing the messaging technology that can track us down in the most sacred spots, such as the VIP Room at the Kit Kat Klub. “The reality, though, is that these things will make us productive only if we learn to take control of them. They are the servants. We are the masters.”

I know this is true, but please don't tell my iPhone. So, starting now, inform your managers that you will only receive their input between 3:00 p.m. and 3:05 p.m. on every third Friday of every second month with an “r” in it.

Your supervisor may complain, but, as I think we've learned, you simply have to focus if you're going to multitask. After all, anyone can screw up one task; however, it takes real talent to screw up three tasks all at the same time.

Bob Goldman has been an advertising executive at a Fortune 500 company in the San Francisco Bay Area. He offers a virtual shoulder to cry on at bob@funnybusiness.com. To find out more about Bob Goldman and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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