Picture yourself driving down the street. Your passenger tells you to turn right. Do you know which way to go? If you are directionally challenged, you're not alone — and it's not because there's something wrong with your brain.

Although we learned left from right when we were teeny tiny — remember doing "The Hokey Pokey"? — that doesn't mean it sunk in for all of us. John R. Clarke, M.D., a professor of surgery at Drexel University, estimates that one out of every five people has some degree of right/left confusion.

"Meaning that they can't immediately tell their right from their left without having to think about it first," he told Outpatient Surgery magazine. "That means if I say, 'Raise your right hand' to a group of people, 20 percent might raise their left or have to take a few moments to think about it."

Surgeons are one group who should definitely have their right and their left straight. After all, if you're on the operating table, you want the correct knee (or hip or wrist) going under the knife.

A famous doctor of a different sort also had problems telling his left from his right: even Sigmund Freud had to figure out "you write with your right."

He wrote:

I do not know whether it is obvious to other people which is their own or other's right or left. In my case, I had to think which was my right; no organic feeling told me. To make sure which was my right hand, I used quickly to make a few writing movements.
Neuroscientist Eric Chudler, executive director of the Center for Sensorimotor Neural Engineering at the University of Washington, points to a study where 71 of 364 (19.5 percent) college professors and 311 of 1,185 (26.2 percent) college students said that they occasionally, frequently or all of the time had difficulty when they had to quickly identify right from left.

Chudler told The Washington Post that 95 percent of the 3,719 people who tried his test reported more difficulty with left/right than with up/down.

Want to see where you fall? On his website, Chudler has an exercise in which you can see how long it takes you to identify if fingers on hands are pointing up or down. After that, you take a similar test to see if the fingers are pointing right or left.knees written on before surgery saying 'it's the other knee

Coping with confusion

In most cases, left/right confusion is rarely a big deal. You can point when you're not sure if you're making the right turn in the car.

But know your directions obviously can be critical if you're a surgeon or a pilot. That's why in key situations, there are plans in place to minimize the chance of problems.

In a health care situation, someone may write "not this leg" on a limb, for example. And in the air, because distractions can cause any number of errors, pilots must avoid all non-essential conversation during the critical phases of flight.

The reason for the muddle

Experts say that right/left confusion is not a type of dyslexia or a neurological disorder, and it doesn't mean you're not smart.

But scientists aren't totally sure what causes the right/left confusion. There does, however, seem to be a link between right/left confusion and brain lateralization — the fact that the right and left halves of the brain each control distinct functions.

Researchers have not found a connection between being directionally challenged and whether you're right-handed or left-handed.

There may, however, be an association with gender. Several studies have found that women are more likely than men to say they are sometimes unable to differentiate between their right and their left. But some researchers say that's only because women are more likely than men to admit they may have a problem.

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Knee photo: Steven Depolo/flickr

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.