Social norm suggesting that the nature of interpersonal interaction is best explained as a system of exchanges of like kinds, i.e. the most likely response to a social exchange is one that is similar or equivalent to the one that stimulated it, either positive and negative. This is the notion of “Equivalent Action.”
Source: Behavioral Science Lab, 2017
Reciprocity is a social norm that involves in-kind exchanges between people—responding to another’s action with another equivalent action. It is usually positive (e.g. returning a favor), but it can also be negative (e.g. punishing a negative action) (Fehr & Gächter, 2000). Reciprocity is an interesting concept from the perspective of behavioral economics, because it does not involve an economic exchange, and it has been studied by means of experimental games (see behavioral game theory).
Reciprocity is also used as a social influence tool in the form of ‘reciprocal concessions’, an approach also known as the ‘door-in-the-face’ technique. It occurs when a person makes an initial large request (e.g. to buy an expensive product), followed up by a smaller request (e.g. a less expensive option), if the initial request is denied by the responder. The responder then feels obligated to ‘return the favor’ by agreeing to the conceded request (Cialdini et al., 1975).
Source: Behavioral Economics