The findings behind the Principle of Reciprocity show that people are more likely to say yes to those whom they feel they owe. This principle, identified by Dr. Robert Cialdini, states that when someone receives a behavior, gift, or service first, they feel an obligation to give back in kind. For example, if a colleague does you a favor, you are more likely to return that favor later. This social obligation increases the likelihood of compliance with requests from those to whom one feels indebted
. One classic demonstration involved restaurant diners who were given a small gift like a mint with their bill. Even such a minor gesture increased the tips left by customers, with personalized and unexpected gifts producing even stronger effects. This shows that people respond not just to the gift itself but also to how it is given, reinforcing the sense of owing and prompting a "yes" response to requests from the giver
. In summary, the research behind reciprocity reveals that people tend to comply with requests from those who have previously given them something, driven by a universal human tendency to repay favors and maintain social balance
