"The 30-Second Rule, A Decision Tree" by Audrey Fukman and Andy Wright.

You Dropped food on the floor, do you eat it?

You know that you’ve been guilty of this before. Accidentally dropping a food item on the floor then claiming the 5 second rule. According to Wikipedia, The five-second rule is a popular polite fiction regarding the eating of food that has fallen to the floor or ground. The substance of the rule is that if food falls on the ground, it may be safely eaten as long as it is picked up within five seconds.
Via Foodie blog