Counting.

My brother Andrew recently needed surgery on his mouth to pull a substantial number of teeth. In the few days leading up to the event, my mother kindly explained to Andrew that the doctors would be putting him to sleep to perform the surgery. She told him that the doctors might ask him to count backwards from 100 and before he knew it, he'd be out cold. "So," she asked, "can you count backwards from 100?" "Yeah," he retorted. "100, 99, skip a few, 1." Now that's one smart kid.