Slightly back to our primitive beginnings here, but if you've ever watched wildlife programmes, or seen animals in the wild, then just observe the way they chastise their young. They do it by walloping them with a paw. And why do they do it? because if the young animal strays beyond the boundary that young animal is likely to be killed. And generally animals live together in harmony, the society that is the animal kingdom is balanced. And while it's true that as humans we have inteligence beyond that of animals, you only have to look at human society to see how different it is without the discipline which exists in more primitive settings.
I actually believe that psychology has been taken too far, because for every argument there is a counter argument. When I was a child, time out was ruled to be an absolute no-no because psychologists then said that it led the child to feel rejected by his/her parents, and it was not advocated as a form of discipline, and yet now time-out is seen to be the answer to many of our discipline problems, so will the tide turn again? in 30 years will someone tell our children that the way they were raised was abusive?
I was smacked as a child, but i was also disciplined verbally. And I don't remember the odd smack, not because I blotted those bits out of my life, but because it was over with in seconds. But I do remember very vividly being shouted at, being told that my parents were "sick of you", being put into time-out for probably longer than is now the recommended amount of time now. And I remember crying myself to sleep at nights because I genuinely believed, after having been told off, that no-one loved me. Just to be clear, I was not abused as a child, and I have absolutely no doubt in my mind that my parents loved me, but I think the words can often hurt a lot more than we think.
I do not smack my own child, I have never had to, and yes I do use time-out, but I always explain why after the event, and then we move on. But that doesn't mean that if my son put his hands up to the cooker I wouldn't smack them to stop him burning himself.