So let's talk about reciprocity. Simply put people are obliged to give to others in the form of behavior, gift or service that they have received first. If a friend invites you to party there's an obligation for you to invite them to a future party you are hosting. If a colleague does you a favor then you owe that colleague a favor and in the context of a social obligation people are more likely to say yes to those that they owe. One of the best demonstrations of the principle of reciprocations comes from a series of studies done in restaurants. Sweetening the till.
The last time you visited a restaurant there's a good chance the waiter or waitress would have given you a gift probably about the same time that they bring your bill a fortune cookie or perhaps a simple mint
Does the giving of a mint have any influence over how much tip you are going to leave them?
Most people will say no but that mint can make a surprising difference. In the study, giving diner's a single mint at the end of their meal typically increased tips by around 3%. Interestingly enough if the gift is doubled and two mints are provided. Tips don't double, they quadruple a 14% increase in tips. But according to the study what is even more interesting. If the waiter provides one mint, starts to walk away from the table but pauses turns back and says "For you nice people here's an extra mint" Tips go through the roof. A 23% Increase, influenced not by what was given but how it was given.
In using reciprocity successfully it is important to be the first to give and to ensure what you give is personalized and unexpected.