Ben Franklin effect
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.
Recognition of effect by Franklin 
In the words of Benjamin Franklin, who famously observed the effect and for whom it is named, "He that has once done you a Kindness will be more ready to do you another, than he whom you yourself have obliged."
In his autobiography, Franklin explains how he dealt with the animosity of a rival legislator when he served in the Pennsylvania legislature in the 18th century:
Having heard that he had in his library a certain very scarce and curious book, I wrote a note to him, expressing my desire of perusing that book, and requesting he would do me the favour of lending it to me for a few days. He sent it immediately, and I return'd it in about a week with another note, expressing strongly my sense of the favour. When we next met in the House, he spoke to me (which he had never done before), and with great civility; and he ever after manifested a readiness to serve me on all occasions, so that we became great friends, and our friendship continued to his death.
Effect as an example of cognitive dissonance 
This perception of Franklin has been cited as an example within cognitive dissonance theory, which says that people change their attitudes or behavior to resolve tensions, or "dissonance", between their thoughts, attitudes, and actions. In the case of the Ben Franklin effect, the dissonance is between the subject's negative attitudes to the other person and the knowledge that they did that person a favor.
See also 
- A more detailed explanation appears at the page on the Ben Franklin effect at changingminds.org.
- From The Autobiography of Benjamin Franklin, as given in Benjamin Franklin: Writings, ed. J.A. Leo Lemay (NY: Library of America, 1987), p. 1404. ISBN 0-940450-29-1.
- Paul Henry Mussen, Mark R. Rosenzweig & Arthur L. Blumenthal (1979). Psychology: an introduction, p.403. University of Michigan. ISBN 0-669-01672-1
- Tavris, Carol; Elliot Aronson (2008). Mistakes were made (but not by me). Pinter and Martin. pp. 28–29. ISBN 978-1-905177-21-9.
Further reading 
- Jecker, John; David Landy (1969). "Liking a Person as a Function of Doing Him a Favor". Human Relations 22 (4): 371–378. doi:10.1177/001872676902200407.
- Schopler, John; Compere, John S. (1971). "Effects of being kind or harsh to another on liking.". Journal of Personality and Social Psychology 20 (2): 155–159. doi:10.1037/h0031689. ISSN 0022-3514.