Template:Reciprocity capsule
Reciprocity: In Robert Cialdini’s survey of the psychology of persuasion, a freebie. The classic example is the free flower from the Hari Krishna at the airport so pleasingly lampooned in Airplane!
The idea is if you receive a gratuity — even an tatty flower you didn’t want, pressed on you by a glassy-eyed hippy when you’re struggling through arrivals with three suitcases and a rolled up Turkish carpet your spouse bought on impulse — you feel morally obliged to reciprocate somehow. If you are in the middle of a sales pitch, the obvious way of doing that is buy buying the product.