Happy Holidays and here’s a little something for the trouble!

I was standing in the Knave reflecting on how much of a tip I should leave our waitress on our twenty-two dollar check for coffee and tea. While the bill was small and we hadn’t required a lot of service, we had just spent an hour and a half at the table talking and taking holiday pictures. “Six dollars on twenty-two is a generous tip”, I thought.
I turned to see the waitress approaching. “Happy Holidays”, she said with a smile as she handed me the credit card receipt. I paused, felt the effects of her statement, wrote in an eight dollar tip, signed the receipt, smiled and replied “Happy Holidays!” The waitress had just increased her tip from $6 to $8 through her simple expression of goodwill. This reminded me of the behavioral science principle of mental accounting.
Unwittingly, the waitress had created an additional debt in my mental account of goodwill which subconsciously influenced a desire in me to repay that debt. Importantly, it was at a decision point where I was determining the amount of money I would leave as a goodwill gesture after lingering at her table for two hours over a few cups of coffee and tea. I had already begun to feel guilty, and thought a six dollar tip on a twenty dollar bill would serve as ample compensation and bring me back to an equilibrium point in my mental account of goodwill. However, that extra expression of goodwill, through a simple “Happy Holidays”, had driven me deeper in debt, and thereby boosted her tip another 25%. The psychological mechanism at work here is guilt mitigation.
Interestingly, Stromehtz, Rind, Fisher & Lynne (2006) have found experimental evidence linking goodwill gestures and tip amounts. In a series of studies the authors manipulated whether restaurant patrons received chocolate mints with their check or not. Among others, their results showed that checks delivered with mints by waiters garnered 14% more in tips on average than checks with no mints. Further, if the waiter turned to walk away and then turned around to provide additional mints (a gesture of goodwill), tips increased an average of 23%. In their article, the authors argue that the effects are due to the psychological mechanism of “reciprocity” rather than simply engendering a good mood in patrons.
Apparently the old adage is true: give and you shall receive, or more recently “you only get what you give”.