Effect on restaurant tipping of a helpful message written on the back of customers' checks

Research has shown that servers can increase their tip percentages by writing 'Thank you' or by drawing a happy face on the backs of customers' checks. In the current study, a third approach of this type was tested. An experiment was conducted in which a female server either did or did not write a helpful message about an upcoming dinner special on the backs of checks before delivering them to customers. It was predicted that adding the helpful message would increase tip percentages because of reciprocity, in which customers would tend to respond to the server's 'tip' with an increased tip of their own. Results were consistent with this prediction: Mean tip percentages increased from about 17% to 20%.