The Rule of Reciprocation

We are taught from birth to repay favors, gifts, hospitality, etc.
(How many times have you said, “We need to invite the “so-and-so’s” over for dinner. We owe them.”)
Robert Cialdini, a social psychologist at Arizona State University, is an international expert in this field. In his book, Influence: The Psychology of Persuasion, he cites several studies.
In one, a social scientist randomly chose names of strangers out of the phone book and sent them all Christmas cards. An astonishing number of these people sent him a Christmas card in return. He didn’t know them and they didn’t know him. Talk about perfect strangers!
In another, two people were assigned a task to do jointly. One of them was a researcher. At some point, the researcher excused himself to go to the bathroom. In some instances, he returned with two Cokes, one for him and one for the experimentee. This was an unbidden favor. In other instances, he returned empty-handed. When the two completed the task at hand, the researcher asked the experimentee to buy some raffle tickets. The results: those who had been given a Coke bought twice as many tickets as those who had not.
The import is that extending favors can induce conduct you want because human beings feel a deep-seated need to reciprocate. How does this work in negotiation? Stay tuned.