University of California Irvine

WASHINGTON - No need to curse that bad driver weaving in and out of the lane in front of you -- he cannot help it, U.S. researchers reported on Wednesday.

They found that people with a particular gene variant performed more than 20% worse on a driving test than people with a different DNA sequence.

The study may explain why there are so many bad drivers out there -- about 30% of Americans have the variant, the team at the University of California Irvine found.

"These people make more errors from the get-go, and they forget more of what they learned after time away," Dr. Steven Cramer, who led the study published in the journal Cerebral Cortex, said in a statement.