The "5-second rule" says that it's OK to eat a piece of food that has fallen on the floor as long as it hasn't been there for more than 5 seconds. Connecticut College biology professor Anne Bernhard has done scientific research into how long food morsels can remain on the floor uncontaminated, and the results may surprise you.
I confess I don't recall the conclusions but several months ago a program on cable called "Mythbusters" examined this question in an extended and entertaining fashion.
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