While economist Bill Harbaugh was on sabbatical in Aix-en-Provence, one of his daughters attended a French school. It was convention that each day before class all students would kiss each other. Harbaugh took this bedrock of French culture and turned it into a simple problem. He posed the following question: How fast can a group of 35 students can kiss each other, given that they only have 10 minutes between classes? (Harbaugh 2003) With this question, Harbaugh opens the door to find and conceptualize an efficient way to solve the ‘kissing problem’. In this paper we first briefly mention an earlier attempt to solve this question. We then provide a more efficient solution and link it to a historically well known problem. Finally, we illustrate how this problem and its framework can be used to introduce topics like matching, networks, and search that are typically not covered in undergraduate classes despite their growing importance. This highlights the pedagogical importance of Harbaugh’s quandary about efficient kissing.
Something to try in class.