Can You Teach a Self-Driving Car That a Snowman Won't Cross the Road?

You go around a curve, and suddenly see something in the middle of the road ahead. Of course, the answer depends on what that'something' is. A torn paper bag, a lost shoe, or a tumbleweed? You can drive right over it without a second thought, but you'll definitely swerve around a pile of broken glass. You'll probably stop for a dog standing in the road but move straight into a flock of pigeons, knowing that the birds will fly out of the way.