Like nose picking, double-dipping is probably something lots of people do when they hope no-one is looking. But is it more acceptable for some dips and less so for others? And is it ever ok to dip the non-bitten but well pawed other end?
Harold McGee, the scientific source behind some of Heston Blumenthal's cooking techniques, recently published a very amusing article on double-dipping (see The New York Times on 30 January 2008). It didn't really help me with all of the above questions but did shed some scientific light on the effects of double-dipping.
McGee reported on a study at Clemson University by Professor Paul Dawson to be published later this year. Professor Dawson's study was inspired by a re-run of a classic Seinfeld episode in which George Costanza is confronted at a funeral reception by his girlfriend's brother after dipping the same chip twice.
In the study volunteers were asked to take a bite of a cracker then dip it into various dips. The remaining dips were then analysed and certain types of bacteria were counted - without determining whether any of the bacteria were harmful.
The study concluded that the actual risks of double dipping are "debatable" and depend on many unknown factors. It was, however, noted that:
(i) on average, three to six double-dips transferred about 10,000 bacteria from eaters' mouths into the remaining dips; and
(ii) the type of dip made a difference - runny dips pick up more bacteria than thicker dips.
Professor Dawson is quoted as follows: "before you have some dip at a party, look around and ask yourself, would I be willing to kiss everyone here? Because you don't know who is double dipping, and those who do are sharing their saliva with you."
I guess we suspected the saliva sharing already. George's girlfriend's brother certainly did, though now he can take some comfort in the actual health risks being "debatable". Partying swingers can look around the room, probably say "yes" to Professor Dawson's question, and double-dip all night. Among the less adventurous, perhaps we'll now see more thicker dips than runny dips and more conspicuous double-dipping of those thicker dips.