Or in layman's terms, they're more likely to become writers. I remember reading that Sue Grafton really did have a frightening childhood, where her world was never made safe by her alcoholic parents. But she'd read scary stories with a kitchen knife at her side. Fearful or kind of uber cool?
I don't know that I buy this "science" I have to say. It's a chicken and the egg argument. It could be that fearful kids just have bigger imaginations. And in that realm of imagination, we can come up with scarier scenarios than those with...say...math brains.
Just like a song writer can make music from nothing, a writer can create worlds from their own imaginations. Don't blame fearful kids -- like they have some kind of fatal flaw because you don't have the creativity to come up with a post-apocalyptic world. I'll bet you Stephen King was a fearful little bugger as a child.
So much of our world tries to label people as if everything is a disease. This is what makes us different!