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.

See also

• the dog in the night time