The Ben Franklin effect is a psychological finding: A person who has done someone a favor is more likely to do that person another favor than they would be if they had received a favor from that person. Similarly, one who harms another is more willing to harm them again than the victim is to retaliate.
Halfway through his autobiography, Franklin tells a story about an up-and-coming member of the Pennsylvania Assembly who had snubbed him on several occasions. Faced with the same dilemma as anyone might be in getting on with a colleague, Franklin decided to win him over and asked if he might borrow a certain scarce book from the Assemblyman’s library. The Assemblyman obliged. Franklin thanked him and from then on, they became best friends. Franklin drew out the lesson that when you ask someone for help and they oblige, they are more willing to do you a further favour in future than if you had been the one helping them.