Animals are perfect examples of classical conditioning. Pavlov and his dog/bell experiment is a great example. Humans work the same. Both animals and humans can be trained to do particular behaviors. A dog could indeed understand and turn to expect a cookie after going outside. If given a cookie every time they went outside, if it were stopped, they'd then be confused because the predictable was suddenly gone. Some of the classical conditioning experiments were frightening, actually...

Kids communicate because they need (or want) something. They understand nothing in terms of social norms and expectations. They want what they want and don't have the developmental capacity to regulate their emotional response. I truly believe any physical punishment damages a child and only silences them, making them fearful of getting "the wrath" of their parent.

Does it stop the behavior? Depends. Does the kid grow and eventually lie? Sneak? Run away from home? Do anything and everything away from their parents' view?

Many do hit. I'm not them, and whomever wants to hit has all the power to do it within legal repercussion. I feel bad enough when I yell, especially when she just doesn't understand. The thought of hitting her before she could actually talk to me makes me sick to my stomach, actually...