"the partial reinforcement effect."
openmedia.yale.edu"What's the very worst thing to do when your kid cries to go into bed with you and you don't want him to go into bed with you? Well, one--The worst thing to do is for any--Actually, for any form of discipline with a kid is to say, "No, absolutely not. No, no, no, no." [pause] "Okay." And then later on the kid's going to say, "I want to do it again" and you say no and the kid keeps asking because you've put it, well, put it as in a psychological way, not the way the behaviorists would put it. The kid knows okay, he's not going to get it right away, he's going to keep on asking. And so typically, what you're doing inadvertently in those situations is you're exploiting the partial reinforcement effect. If I want my kid to do something, I should say yes one out of every ten times. Unfortunately, that's the evolution of nagging. Because you nag, you nag, you nag, the person says, "Fine, okay," and that reinforces it."