It totally stinks that an uninvited favor is just as powerful, and just as meaningful, as an invited one.
Does that make sense?
If you cut my grass for free – even though I insist you shouldn’t – an obligation is created on my end. And I am in your debt until this obligation it is paid back in an adequate manner.
I do not want extra mailing labels, and neither do you. But do you think it is an accident that free labels are included with mailed donation requests?
Just please don’t come cut my grass…
Earlier we suggested that the power of the reciprocity rule is such that by first doing us a favor, strange, disliked, or unwelcome others can enhance the chance that we will comply with one of their requests. However, there is another aspect of the rule, besides its power, that allows this phenomenon to occur. Another person can trigger a feeling of indebtedness by doing us an uninvited favor. Recall that the rule only states that we should provide to others the kind of actions they have provided us; it does not require us to have asked for what we have received in order to feel obligated to repay.
-Robert Cialdini, Influence