A COUPLE of weeks ago I saw a new scientific paper from Clemson University that struck me as both pioneering and hilarious.

Accompanied by six graphs, two tables and equations whose terms include “bologna” and “carpet,” it’s a thorough microbiological study of the five-second rule: the idea that if you pick up a dropped piece of food before you can count to five, it’s O.K. to eat it.

I first heard about the rule from my then-young children and thought it was just a way of having fun at snack time and lunch. My daughter now tells me that fun was part of it, but they knew they were playing with “germs.”

We’re reminded about germs on food whenever there’s an outbreak of E. coli or salmonella, and whenever we read the labels on packages of uncooked meat. But we don’t have much occasion to think about the everyday practice of retrieving and eating dropped pieces of food.