Well, this explains everything. Scientists scientifically studied the brains of 29 people. Of those, 22 had normal brains while the other seven had a genetic variant that stops their brain from secreting something called a neurotrophic factor (BDNF). Without the BDNF, new memories aren't formed properly. And people with this gene variant also can't drive.

Those 29 people were placed in cars on a closed-circuit course with lots of difficult turns. Then they repeated the test four days later. Results? Not only did the gene variant-brained people do worse on the first day of testing, they did worse on the second day, too.

And now the kicker – 30% of Americans have this genetic variant. Said the scientist in charge, "I'd be curious to know the genetics of people who get into car crashes. I wonder if the accident rate is higher for drivers with the variant." As it stands now, there is no commercially available test to check for this variant. In other words, be careful out there.

[Source: CNN | Photo: David Livingston/Getty Images]