My sister, Monica, told me this story and it cracks me up.  It’s such a perfect illustration of human nature.

She was at a professional conference, standing at the back of the room near the table with coffee and doughnuts. A well groomed woman came up to the table, and as she reached for a doughnut she accidentally bumped it, knocking it to the floor. The woman looked around quickly, then stooped to pick it up.  She stood there holding it uncertainly, looking a little embarrassed.

“That’s okay,” Monica assured her with a wink. “…Ten second rule.” 

“What’s that?”

“Well if something drops onto the floor and it’s there less than ten seconds it’s okay to eat it.”

“Oh…” The woman smiled with uncertain relief, and nodded.  Then she replaced the dropped doughnut onto the plate and picked up a different one for herself.