Persuasion works by appealing to certain deeply rooted human responses. Experiments in social psychology by Robert Cialdini and others have identified six of those responses, which Cialdini initially described in his book Influence.
If people like you—because they sense that you like them, or because of things you have in common—they’re more apt to say yes to you.
People tend to return favors. If you help people, they’ll help you. If you behave in a certain way (cooperatively, for example), they’ll respond in kind.
People will do things they see other people doing—especially if those people seem similar to them.
Commitment and consistency
People want to be consistent, or at least to appear to be. If they make a public, voluntary commitment, they’ll try to follow through.
People defer to experts and to those in positions of authority (and typically underestimate their tendency to do so).
People value things more if they perceive them to be scarce.