People are inherently social. Our ability to form personal cooperative relationships is one of the keys to our success as a species. These relationships are built up through layers and layers of individual interactions. Whether each interaction is brief or long, casual or meaningful, they all contribute to the nature of the relationship.

The strength of a relationship can be considered to be a weighted sum total of these interactions, and contrary to the opinion of Sheldon from “Big Bang Theory“, each exchange is additive. For example, the simple repeated interaction of a mutual “good morning” every day for years often results in a stronger relationship with your neighbor than a polite greeting to a stranger.

The principle of reciprocity is what allows one side to initiate an exchange, and turn it into a mutual interaction. As explained in “Principles of Persuasion“, when one initiates an exchange, an obligation is created. There is a powerful socially conditioned response to honor this obligation, presumably because it is on this basis that the success of our species to create cooperative social relationships was built. If I help you with something now, you’ll help me with something later.

Surprisingly, the need to satisfy the obligation often overrides the importance of that “something” being equal. If you borrowed a dollar from me yesterday, it seems equal that I could ask to borrow a dollar from you today. But suppose you’ve always given me good advice when I needed it, and today you need help moving? How do we evaluate concepts such as thoughtfulness, context, and intention? When faced with complex valuations, we often fall back to generalizations and simply fulfill the obligation, even if the value is not equal!

So, relationships are composed of interactions, the principle of reciprocity motivates us to fulfill obligations, and exchanges are often complex and can be unequal. When developing relationships remember to look for everyday opportunities to create a thoughtful exchange in a meaningful way and you may be surprised at how your relationships grow and give back more than you expected!