Answer to Question 1
Answer:
The reciprocity principle uses the norm of reciprocity, a very basic human response to return a favor. One tactic that uses this principle is the door-in-the-face technique. The idea is the requester initially makes a huge request that can only earn a door in the face. But then the requester follows up with a much smaller request. Because it now appears that the requester has made a concession, the requestee is drawn toward a reciprocal concession.
In the that's-not-all technique, an initial request, perhaps an offer to sell something at given price, is made. Before the requestee has enough time to respond, the requester offers to throw in an extra incentive, perhaps a free gift. Again, similar to door-in-the-face, the requestee has an immediate response to reject the initial offer, but when the sweetener is added (before s/he even has a chance to say no), the requestee feels like a concession has been made, and his reciprocity response kicks in.
Answer to Question 2
Answer:
1) The foot-in-the-door technique: make a small request. Once compliance is gained, make a larger request (the one that was originally desired). This works because refusal of the larger request is inconsistent with granting the initial request.
2) The lowball procedure: offer a very advantageous deal to someone. Once they have accepted, change the terms so that they are less advantageous. The initial commitment makes it more difficult to refuse the modified deal because subsequent refusal would be inconsistent with the initial acceptance.