Sadly, I believe that the idea of yelling is a primitive way of disciplining. We all know that we have 2 instinctual responses and that is why it doesn't work. We all understand that all living beings with a brain will respond to a "threat" in its immediate environment. When you yell at a child, it makes them want to fight you or run away.

Also, the parent yelling is doing nothing more than using force. It's this same idea that we use to "train" a dog. Yell, and punish for bad behavior. Spank the dog when it poops in the house etc, etc. If you want to assert your will on a wild bear instead of your child, you can try to use force but it wont work. Maybe on a dog, or a cat, or a rabbit.. because they have less physical mass than you. This is the reason we are able to yell and scream at kids. But when they grow up and they get bigger than you, that can change. And at that point you better hope you never used physical discipline because when you strike someone they want to strike you back.

Love is the way of teaching. Society has not necessarily taught us the correct way of raising children in my opinion. It was only 1 generation ago that teaches were able to abuse children in public. All the older generation thinks we are all brats in this era because the government doesn't allow them to beat their children anymore. I am raising a child and I dont smack them like my parents did me. I use intellect and try to be as honest and up front with my child as possible. I try to be straight forward and explain things. Sure, I still get angry, which is a huge fault of mine that I am working on. But I believe my daughter will grow up to raise her children without physical punishment and yelling.