( CNN ) -- The next time you see a motorist obliviously straddling two lanes , do n't fault bad driving , but genetics . In a study published recently in the journal Cerebral Cortex , researcher Steven Cramer found that people with a certain gene variant performed more than 30 percent worse on a driving test than people without it . The study by Cramer , a neurology professor at the University of California Irvine , might also help explain why there are so many bad drivers on U.S. highways : About 30 percent of Americans have the variant . Ordinarily , when a person performs a task , a protein called brain-derived neurotrophic factor ( BDNF ) is secreted to the area of the brain that is associated with that activity . The protein helps facilitate communication among brain cells and helps retain memory . However in people who have the gene variation that Cramer studied , BDNF secretion is limited . `` These people make more errors from the get-go , and they forget more of what they learned after time away , '' Cramer said in a statement . Cramer and his team of researchers set out to find how the variant affected driving . They recruited 29 people to drive 15 laps on a simulated course with difficult curves and turns . Twenty-two of the participants did not have the gene variant ; seven did . The researchers wanted to see how effectively the participants learned to navigate the twists and turns in each subsequent lap . Four days later , they repeated the test . The participants with the variant did worse both times . They also retained less the second go-round . `` I 'd be curious to know the genetics of people who get into car crashes , '' Cramer said . `` I wonder if the accident rate is higher for drivers with the variant . '' Unfortunately , a test to determine whether someone has the gene variant is not commercially available .
Study finds bad driving may have genetic basis . Those with certain genetic variants performed worse on the test that those without it . Nearly 80 percent of Americans have variant , according to study .