Ben Franklin effect

The Ben Franklin effect takes place when we tend to like a person more after we do them a favor. This is because we try to tell ourselves that we actually do like them after the favor, so we keep doing nice things. The same can be said when we hate the person. We keep hating them and eventually we chop their head off.

This is how Franklin won over a political opponent:

I did not... aim at gaining his favour by paying any servile respect to him but, after some time, took this other method. Having heard that he had in his library a certain very scarce and curious book, I wrote a note to him, expressing my desire of perusing that book, and requesting he would do me the favour of lending it to me for a few days. He sent it immediately, and I return'd it in about a week with another note, expressing strongly my sense of the favour. When we next met in the House, he spoke to me (which he had never done before), and with great civility; and he ever after manifested a readiness to serve me on all occasions, so that we became great friends, and our friendship continued to his death. This is another instance of the truth of an old maxim I had learned, which says, "He that has once done you a kindness will be more ready to do you another, than he whom you yourself have obliged."

The moral? Ask people to do you a small favor, but don’t immediately return it. And when people ask you for favors, watch out for feeling better about them.