Not long ago, a team of researchers watched a 1-year-old boy take justice into his own hands. The boy had just seen a puppet show in which one puppet played with a ball while interacting with two other puppets. The center puppet would slide the ball to the puppet on the right, who would pass it back. And the center puppet would slide the ball to the puppet on the left . . . who would run away with it. Then the two puppets on the ends were brought down from the stage and set before the toddler. Each was placed next to a pile of treats. At this point, the toddler was asked to take a treat away from one puppet. Like most children in this situation, the boy took it from the pile of the “naughty” one. But this punishment wasn’t enough — he then leaned over and smacked the puppet in the head.
New York Times Magazine has a superb article on The Moral Life of Babies. It's not entirely nature over nurture, but it does seem to overturn a lot of what i thought I knew about childhood development.
The last sentence in the above quote made me laugh out loud on the Tube.