Ben Franklin Effect

The Ben Franklin effect refers to an altruistic reaction that makes a person more likely to do a favor for someone that they have already completed a favor for; more likely than they are to return a favor to someone who has completed a favor for them. This phenomenon is named this from the observation in the autobiography of Benjamin Franklin: "He that has once done you a kindness will be more ready to do you another, than he whom you yourself have obliged."

An example of this might be loaning tools to a neighbor who has borrowed from you before, while a co-worker's approach for a loan of a tool might be rejected even though they have done favors for you in the past.