> Rattenborg found that ducks with a bird on either side of them put their entire brain to sleep and kept both eyes closed. "However, the ducks at the end of the row slept more with one half of the brain at a time," he says. "And when they did that they directed the open eye away from the other birds, as if they were looking for approaching predators."

When I park my semi truck in a truck parking lot in late afternoon or evening, if the space on either side is empty I leave my parking lights on, until both spaces are filled.

And if I'm unlucky enough to park on the end of the row, I leave my parking lights on all night long. And go to sleep with half my brain awake.