Scott Hanselman explores the Five Second Rule (“…if you drop something on the ground, you can still eat it if you pick it up in five seconds”) And the Line Of Sight Corollary (“extend the Five Second Rule as long as you held the dropped object in your line of sight the entire time”).
I had never considered whether it’s an international phenomenon. Apparently not.
Ed Bott (@ wordpress.com) 
It’s garbage … many tests have been done to disprove this rule (maybe the most popular being the one carried out by the Mythbusters). What’s more important than how long something has been on the floor is what’s been there before. 😛
The common corollary for this is the Iron Stomach Rule: Do you have the kind of stomach that can stand up to whatever’s been dropped on the floor? (I’ve got a story in that regard about a friend who dropped a Subway sandwich on a New York sidewalk… but it’s NFSW.)
Considering what I’ve seen my dogs and cats eat, I’m not terribly concerned with the five second rule, unless it falls on something I would find objectionable. I’ve been known to chase M&Ms under my desk.
I’ll use a pseudonym this time if I may. In the restaurant business we call it the three second rule. Can be expanded beyond three seconds in extreme cases. Happy dining! 🙂
It’s not exactly a rigorous scientific study, but FYI, a couple of students at Connecticut College conducted some short tests of the “5 sec. rule” which might actually be valid up to ca. 30 sec. in some circumstances. you can check out a new report of it at the link below, or a Google search of “Connecticut College five second rule” will turn up numerous pages referencing the same study.
http://aspen.conncoll.edu/camelweb/news/3464.cfm