A few years ago when my family and I were holidaying in NYC, we were stopped on the street by a man thrusting hats into our hands. Being naïve at the time to the power of the rule of reciprocity, my family and I duly accepted the hats. It was then of course that the man asked if we would kindly donate to a homeless charity. Feeling the pressure rise we felt compelled to donate at least a few dollars to the charity in question – An excellent use of the reciprocity rule on the part of the charity worker. Indeed, this rule has been proved effective in numerous scenarios, with Robert Cialdini (2009) documenting the case of the Krishna religious sect boosting their donations massively upon handing out flowers as ‘gifts’ in an airport. Empirically, support has been given from Regan (1971) who had two individuals taking part in an experiment on art appreciation. In reality, one ‘participant’ was actually a confederate who acted in two different ways: With some participants he bought a coke for himself and with others, he bought a coke for himself and the participant. Later, the confederate asked the participant if they would be willing to buy some raffle tickets. Regan found that participants who had been given the coke bought twice as many raffle tickets, even though the raffle tickets were more expensive than a can of coke! 
Figure 1 – Regan (1971)Further evidence comes from Rind and Strohmetz (1999) who investigated reciprocity through the inclusion of a helpful message with a restaurant bill. Participants were either given a bill as usual or a bill with a message informing them that there was a special dinner featuring excellent seafood on a specified date. It was found that the mean tip percentage was higher in the message condition. This can be explained through the reciprocity rule because the waiter has informed the customer of something which is interpreted as helping behaviour. As such, the customer feels indebted to the waiter so increases their tip.In conclusion, the reciprocity rule is very effective in inducing compliance. Individuals are motivated to comply to a request because they feel indebted to the requester. ReferencesCialdini, R. B. (2009). Influence: Science and Practice. Boston: Pearson Education. Regan, D. T. (1971). Effects of a favour and liking on compliance. Journal of Experimental Social Psychology, 7, 627-639.Rind, B., & Strohmetz, D. (1999). Effect on restaurant tipping of a helpful message written on the back of customers’ checks. Journal of Applied Social Psychology, 29, 139-144.