Source: http://ca.news.yahoo.com/blogs/geekquino...

Their findings showed that the amount of time the food is in contact with the floor has a big effect on how much bacteria is picked up. Also, the lowest chance of picking up bacteria is for food dropped onto carpet, while the highest chance is for moist food dropped onto wood or tile and left there for longer than five seconds.

"Consuming food dropped on the floor still carries an infection risk as it very much depends on which bacteria are present on the floor at the time," Hilton said in an Aston University press release. "However the findings of this study will bring some light relief to those who have been employing the five-second rule for years, despite a general consensus that it is purely a myth."

"We have found evidence that transfer from indoor flooring surfaces is incredibly poor with carpet actually posing the lowest risk of bacterial transfer onto dropped food."