A new study is rekindling one of the most heated debates in parenting — should you ever spank a child? The researchers, whose work was published in the journal Pediatrics, concluded that spanking small children can make them more violent. Of the 2,500 mothers studied, over a quarter spanked their children regularly. Children spanked at age 3 were 40 percent more likely than their unspanked peers to be aggressive two years later, at age 5. Does this mean parents should give up spanking once and for all? (Watch a CNN report about the spanking study)

This is the the last strike for spanking: Spanking teaches children to solve problems with violence, says Alice Park in Time, so it's hardly surprising that spanked children are more aggressive later in life. Spanking instills "fear rather than understanding" — alternatives, such as time-outs, teach children to think about their behavior rather than "blindly" acting out.
"Spanking kids leads to aggressive behavior, says study"

Don't bash spanking just yet: While I've never spanked my children, I have friends who spanked their kids, says Lisa Cianci at the Orlando Sentinel. Those kids, now in their teens, "seem perfectly delightful." While the thought of physically hurting a child "makes me sick," it's entirely possible there are some particularly unruly children "who only respond to that punishment."
"Does spanking make children aggressive?"

Wait a minute — not all spanks are created equal: Sure, spanking in a fit of rage is bad, says Dr. Dathan Paterno at Desperately Seeking Parents. But parents who are "calm" and "self-controlled" when they deliver the occasional swat to the bottom — and use time-outs in conjunction with the spank — instill respect, authority, and a "modicum of fear." Such measured discipline is "never going to develop a pattern of violence in a child. Never."
"Again with the spanking..."