Can Spanking Cause Aggression?

Pay particular attention to this part of the story....

They found that spanking seemed to be associated with more aggressive behavior and increased anxiety in all of the countries. The association was weakest in Kenya, where physical punishment is culturally accepted and common. It was strongest in Thailand, where the culture generally discourages spanking.

So in countries where spanking is accepted, children weren't as aggressive. I take this to mean they were better behaved? Hhmmmm...Interesting.