As a fan of Seinfeld, I thought that this study was entertaining and informative. It turns out that double-dipping a chip really IS like putting your whole mouth in the dip.
The Seinfeld reference comes from an episode in which George goes to a funeral, and one of the other people there is aghast that George dips a chip, takes a bite, and then dips it again. This study found that “sporadic double dipping in a cup of dip would transfer at least 50 to 100 bacteria from one mouth to another with every bite.”
So there you go. In related news, this same researcher, who works at Clemson University and apparently has made a bit of a hobby of exploding popular myths, published a study last year on the five-second rule. The results? I wouldn’t eat anything off the ground, if I were you. Especially if it is a large piece of meat that drops out of your gyro late at night while you are standing at one of the most heavily-trafficked tram and metro stops in Prague. This may sound hypothetical, but it has already happened once. So if you find yourself in that position, you know what to do.