It's a foot in the door, you obtain a little something to obtain much more afterward. It's because we tend to not contradict ourselves and act the way we acted

It's a foot in the door, you obtain a little something to obtain much more afterward. It's because we tend to not contradict ourselves and act the way we acted, because doing otherwise would be irrational, right? :D "I've started to talk to this stranger, there is no reason I stop now". Of course there must be a ground for agreement in the first place, you cannot force someone to do something he absolutely doesn't want to do with this technique.