@Briancrc,
One thing about operant conditioning that I've always believed is that physical punishment can, to some extent, deter behavior.
If you take a 4-year old, hook him up to 110 volts, and shock the **** out of him every time he says "milk," then chances are good that, after a spell, you won't here him saying "milk" anymore. At least not while he's hooked up to that machine.
You might trick him a few times, after he's supposedly learned his lesson, by offering him a glass of milk when he's thirsty, but asking him to tell you what it is first. Then, when you finally induce him to say "milk," you once again shock the piss out of him. After that, he aint even gunna answer ya, thirsty, or not.
Spare the rod and spoil the child, and all that there, eh? Somehow, people figured that out a long time ago without the aid of "science." God only knows how.