Ben Franklin effect
n.— «Giving can lead to other forms of involvement: Volunteering, advocacy. And vice-versa. It’s called the Ben Franklin Effect. Because Franklin once said: He that has once done you a kindness will be more ready to do you another, than whom you yourself have obliged.”» —“The more they give, the more they love you” by Jeff Brooks Donor Power blog Nov. 2, 2005. (source: Double-Tongued Dictionary)