Corporal punishment is more effective for changing "bad" behavior. A simple scolding doesn't really bring it home to me in the same way that a spanking does. The pain and crying results in my will being softened to the point that what he's saying actually gets through to me. I feel properly chastised, and my response afterwards is positive in that I mean it when I say I'm sorry and won't do it again. Positive reinforcement doesn't have much effect on my behavior. I don't do good deeds with the expectation of a reward. I do nice things for people I care about because it makes them happy, which is its own reward.