Is a psychological phenomenon that causes us to like someone more after we do that person a favor: We justify our actions to ourselves, that we did them a favor because we liked them.
But the reverse effect is also true - we come to hate our victims, which helps to explain wartime atrocities.
It suggests that holding 2 or more contradictory beliefs at the same time causes people to experience mental discomfort, which manifests as psychological stress.
And people will always seek to minimize their cognitive dissonance and the discomfort it creates.
The Benjamin Franklin effect has generally been explained using the cognitive dissonance theory.
Essentially, this means that when someone does you a favor, they need to be able to justify it to themself, in order to avoid the cognitive dissonance that might occur from doing something nice for someone that they dislike.