According to my handy pediatrician's guide to child rearing, babies are born with a reflex that enables them to dodge objects being thrown at them. Page 147 of "Caring for Your Baby and Young Child":
"Although you may think of your baby as utterly defenseless, he actually has several protective reflexes... if an object comes straight toward him, he'll turn his head and try to squirm out of its way. (Amazingly, if the object is on a path that would make it a near miss instead of a collision, he will calmly watch it approach without flinching.)"
This brings to mind an image of several doctors throwing things at babies and seeing if they duck.
"Did you see him watch that beer bottle just pass on by, an inch from his face?! Amazing!"
"Good throw, Dr. Johnson!"
"Little Jany dodged that ice pick really well- too bad it bounced back off the wall and got her from behind..."