You might have seen Rep. Eric Massa making the rounds on TV after his resignation from Congress this week. His appearance on Glenn Beck was some of the best reality TV in decades (the best summary of this exchange was, unsurprisingly, Jon Stewart which was off color enough that I'll link rather than embed). During his interview with Beck Massa admitted to "groping" a male staffer but innocently so, it was in the middle of a tickle fight.
So thanks to Massa tickling is back in the news. For example, surf over to this article--Why Do We Tickle?--by Brian Palmer.
Scientists don't know why we tickle. We do know a few things, however. First, we know that tickling provokes laughter. Not just in humans, all primates seem to tickle-to-laughter. Second, we know it is hard to tickle yourself. Try it. But make sure no one is watching you...
The difficulty in tickling yourself seems to suggest that tickling is a form of social bonding and communication. To be tickled you need someone else, pleasurably so.
Beyond that, we don't why we tickle. In his article Palmer reviews a few of the theories out there. One theory suggests that tickling can be a dominance display. I've written before about how humor is often a form of power and dominance. Palmer notes how tickling in primates is often a part of dominance interactions, the laughter helping to signal that the interactions will not lead to aggression. That is, laughter is a submissive gesture similar to the human smile. We also know that tickling can be unpleasant and aggressive. You can "over tickle" and people, despite the laughter, often resist being held down and having tickling forced upon them.
Palmer goes on to discuss the role of sex in tickling. Tickling is often a form of flirtation. Palmer summarizes the work of Robert Provine whose book Laughter is a must read:
Based on a survey he conducted for his fascinating book Laughter, neuroscientist Robert Provine notes that adults and adolescents are seven times more likely to be tickled by members of the opposite sex. When asked whom they would most like to be tickled by, there was a fifteenfold disparityWhatever tickling is, it is, as most human interactions, extraordinarily complex, an odd stew of sex, aggression and friendly intimacy. Tickling, thus, is a moral activity. It requires great judgment and care. Just ask your Congressman.