Ben Franklin Effect
A proposed psychological phenomenon where a person who has already performed a favor for another is more likely to do another favor for the other than if they had received a favor from that person.
Origin
The effect takes its name from an anecdote in Benjamin Franklin's Autobiography (written in the 1780s). Seeking to disarm a rival in the Pennsylvania Assembly, Franklin borrowed a rare book from the man's library; the rival lent it, Franklin returned it graciously, and the two became lifelong friends. Franklin credited an "old maxim": he that has done you a kindness will be ready to do another. Psychologists Jecker and Landy confirmed the effect experimentally in 1969, and the Ben Franklin effect is now explained through cognitive dissonance theory.