Should you avoid double dipping? Truths about germs and food safety

If you dunk a chip into a bowl of salsa, bite it, then dunk again, are you spreading your germs all over the communal dip? If you drop food on the floor, pick it up, and eat it in five seconds -- is that safe? Is it better to use a hand dryer or paper towel after you wash your hands? We speak with the author of “Did You Just Eat That?: Two Scientists Explore Double-Dipping, the Five-Second Rule, and other Food Myths in the Lab.”