THURSDAY, Oct. 29 (HealthDay News) -- Are you a bad driver? Maybe you can blame it on your genes.

In a small study, researchers found that people with a gene variation performed 20 percent worse on simulated driving tests and did as poorly a few days later. Almost one in three Americans have the variation, the team said.

"These people make more errors from the get-go, and they forget more of what they learned after time away," said Dr. Steven Cramer, neurology associate professor at the University of California at Irvine and senior author of a study published recently in the journal Cerebral Cortex, in a statement.

The study authors say the gene variation lowers available levels of a protein that boosts memory by helping brain cells talk to one another and work properly.

Earlier research has suggested people with the variation engage smaller areas of the brain when they take on tasks.

"We wanted to study motor behavior, something more complex than finger-tapping," said Stephanie McHughen, a graduate student and lead author of the study in a statement. "Driving seemed like a good choice because it has a learning curve, and it's something most people know how to do."

Twenty-nine people took a driving test on a simulator, including seven with the gene variation. They had to learn to "drive" on a track that included tough-to-navigate curves and turns. They came back four days later to retake the test.

Those with the variant did worse and failed to remember as much the second time around as the others. "Behavior derives from dozens and dozens of neurophysiologic events, so it's somewhat surprising this exercise bore fruit," Cramer said.

But don't be alarmed if you think you have this gene variation -- it has it's good side. The researcher say the gene also slows mental decline for people with conditions such as Parkinson's disease, Huntington's disease or multiple sclerosis.

"It's as if nature is trying to determine the best approach," Cramer said. "If you want to learn a new skill or have had a stroke and need to regenerate brain cells, there's evidence that having the variant is not good. But if you've got a disease that affects cognitive function, there's evidence it can act in your favor. The variant brings a different balance between flexibility and stability."

More information

There's more on safe driving at the U.S. Department of Veterans Affairs.