Another, from the Journal of Aggres

Another, from the Journal of Aggression, Maltreatment and Trauma, found that corporal punishment doled out from the mother was independently related to a decrease in cognitive ability relative to other children. Corporal punishment had the largest effect on children 5 to 9.

Behind all this science-speak is the sobering fact that corporal punishment is damaging to children. That gray matter we've been spanking out of them? It's the key to the brain's ability to learn self-control.