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The ‘five-second rule’

A survey of 2000 people found that 79% would eat food that had been dropped on the floor. According to the ‘five second rule’, a western cultural theory, people believe that food is still safe to eat if it’s only been on the floor for a few seconds. But how true is this?

Newspaper headline: Five-second rule for food dropped on the floor approached by germ scientists. Expert Professor Anthony Hilton says morsels swiftly retrieved from ground are safe to eat Headline from The Independent

Your students might be surprised to find out that Professor Anthony Hilton, from Aston University, said that “although retrieving these morsels can never be completely without risk, there is little to be concerned about if the food is only there momentarily.”

On the other hand, a study by scientists at Rutger University found that food can pick up bacteria almost as soon as it hits the floor particularly depending on the type of food and the surface it’s hit, and that it is not worth the risk.

So should we worry about such exposure, or is our obsession with hygiene causing us to be vulnerable to illness? These sorts of discussions could interest your students and provide a relatable context for understanding scientific concepts.


Consider what ideas perpetuate in your culture or classroom. Do any link to scientific concepts you’re teaching?

We’re looking at microbiology this week. You could introduce microbial inhibition practicals following a class debate on Should we ban advertising of antimicrobial cleaners?

For this activity, don’t be restricted by microbiology as the topic. Share your suggestions of what debates could support understanding of a practical concept for this or another topic in biology.

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This article is from the free online course:

Teaching Practical Science: Biology

National STEM Learning Centre