Almost every person at some point in their life has been told about the five second rule, where a piece of food that has been dropped on the ground, stays germless for five seconds. That means that you would have five seconds to pick up your dropped piece of food before it would become "bad to eat", but how much truth is in this statement?
Through some of the principles of critical thinking, this statement can be evaluated. The most important principle for this claim is principle #5, which states that extraordinary claims must have extraordinary evidence. A correlation, between the amount of time a piece of food has spent on the ground and illness rate after consumption, has caused people to believe that the five second rule is true. However, since correlation does not equal causation, there needs to be more evidence, because there could be an unidentified third variable that is the foundation of the correlation, the third variable problem. Studies have also shown that bacteria diffuse at an almost set rate, so the longer something is on the ground the more bacteria it will pick up. These studies bring up arguments that lead to confirmation bias, where the researchers unknowingly support their views by denying evidence, dismissing evidence, or even distorting it to fit their own theory. In this case they often times say that the food is safe, because the bacteria count is negligible. This extraordinary claim, however, requires extraordinary evidence that is more meaningful than a correlation, with no further data, and an open ended study to prove it true, and that is why this principle of critical thinking is the most useful way to evaluate the claim.
Recent experiments have shown that there is some truth to the five second rule, but if the piece of food is dropped on a site of E. coli or salmonella bacterium, it will diffuse at a rate that would make the food very dangerous, therefore, if the food spends anytime on the ground, it is unsafe!
Learn more at http://www.snopes.com/food/tainted/dropped.asp, http://www.cbsnews.com/stories/2006/07/04/health/webmd/main1774287.shtml, http://www.nytimes.com/2011/03/01/science/01qna.html, and https://docs.google.com/a/umn.edu/viewer?a=v&q=cache:BrqynEsaiVYJ:depts.noctrl.edu/biology/courses/101/handouts/AR2.pdf+dawson+cox+black+simmons+journal+of+applied+microbiology+2007&hl=en&gl=us&pid=bl&srcid=ADGEESiNzTjLZtZf1gSr5sS8yQPVciuArzJabBpzPAWPqdf7_2atJiIFVAAEhZ-gLfk2h0Xe4UK043KWIHSW5P-7WEAmgIaVtOQE55XNNYja9Mgmr0K8OtV3aWq6cJNt63BWpdDXoicZ&sig=AHIEtbSVFJOOgBX7Fhd2p_WDzSL0NG4UnQ