The five-second rule: old wives' tale or science? According to a professor of microbiology at Birmingham, England's Aston University, the answer is ... it depends on whether you're in your bedroom or kitchen. Anthony Hilton and his biology students looked at two types of bacteria (E. coli and Staphylococcus aureus) on three flooring options: carpet, laminate, tile. Toast, pasta, a cookie, and a "sticky sweet" were dropped on the various surfaces and rested there for 3 to 30 seconds. When it came to the transfer of bacteria, both time and flooring type played a role.
Bacteria were least likely to hop aboard the fallen bite if carpet was involved; when "moist" foods hit laminate and tiled surfaces, bacteria was more likely to transfer when contact was made for more than 5 seconds. The upshot, per Hilton: "We have found evidence that transfer from indoor flooring surfaces is incredibly poor." That's likely welcome news to the 87% of people the students surveyed who reported a willingness to adhere to the five-second rule. Writing for Forbes, Alice Walton notes that the findings should be taken with a grain of salt—preferably one not dropped on the floor. She points out that the study doesn't seem to have been peer-reviewed or accepted for publication anywhere. (A previous report on the topic noted that food dropped on the sidewalk was likely safer to eat than that on the kitchen floor.)