This year’s Ig Nobel Prize in biomechanics went to researchers trying to answer a surprisingly complicated question: what’s a kiss? Their definition—”non-agonistic interactions involving directed, intraspecific, oral-oral contact with some movement of the lips/mouthparts and no food transfer”—was concocted to exclude such exchanges as ants feeding each other with their mouths, bees and birds vomiting at one another, and fish that fight by smashing their open jaws together.
Defining a kiss might seem like a silly scientific endeavor, but it was a crucial first step for their research.