There is an overwhelming urge to repay debts, to do something in return when something is done for us. This deep-seated urge is so strong, noted paleontologist Richard Leaky has said that it is the very essence of what it means to be human. Sociologist Alvin Gouldner points out that no society on Earth escapes the reciprocity principle.

We are driven to remain consistent in our attitudes, words, and actions. So, when we are led to make a commitment of some kind, to go on record or take a stand or make a decision, there is an urge to remain consistent with that original commitment later on. The key is to get the initial commitment, which can appear small, reasonable, and innocent. This commitment can not only lead to compliance via the principle of consistency, but also to further compliance for larger requests.