Influence: The Psychology of Persuasion
Robert cialdini's seminal book on the psychological techniques of persuasion list 6 types of persuasion.
- reciprocity: the classic example being the free flower from the hari Krishna at the airport so pleasingly lampooned in airplane. The idea is if you receive a gratuity, regardless of how insignificant, you feel morally obliged to reciprocate, (in the context of sales by purchasing the product)
- commitment and consistency:
- authority,
- social proof,
- liking
- scarcity, and more recently
- unity.
It should not come as an enormous surprise that a combination of these techniques is particularly effective. The same techniques can be used to good ends and ill: many are staples of unscrupulous salespeople. Some are especially susceptible to fraudsters.