After more than 200 years, Congress has finally forced America to confront the question: Is it gay for one dude to tickle another dude? Freshman Rep. Eric Massa resigned Monday amid claims that he sexually harassed junior male aides. Appearing on Glenn Beck, Massa admitted that he "groped" a male staffer and "tickled him until he couldn't breathe" in their shared Washington townhouse. Larry King posed the inevitable question to Massa on Tuesday: "Are you gay?"
Determining the social significance of Massa's behavior requires a dive into the science and history of tickling: Where did it come from? Why do we do it? Do other animals tickle? Is adult tickling necessarily sexual? Can you really suffocate someone through tickling?
The practice of manually stimulating others to elicit laughter is older than we are as Homo sapiens. All four species of great apes engage in tickling. Jane Goodall observed it among the chimpanzees at Gombe, and Dian Fossey watched young gorillas caress one another's bellies while panting wildly. Researchers assume that our common ancestor—who lived between 10 million and 16 million years ago—also practiced the tickling arts in the trees of Africa or Asia.
Tickling—or at least being ticklish—might be older still. While rats aren't known to coax laughter from one another, they do exhibit many of the same behaviors as primates when tickled by a human hand. They writhe, struggle, and withdraw but usually come back for more. They also make a repetitive ultrasonic chirping noise that may represent murine laughter. Until we can successfully tickle more of our distant mammalian cousins, though, we won't know whether a common ancestor with rats was ticklish or if rats independently evolved the trait. (Lots of animals, including sharks, exhibit knismesis, a mild pleasure response to light stimuli like a feather being dragged across the back of the neck. This seems to operate via a different mechanism from gargalesis, the laughing response to more forceful touching.)
It's easy to see how it might be beneficial for animals to experience pain in response to a violent stimulus. But what's the point of feeling ticklish? No one really knows. One clue comes from the fact that it's so difficult to tickle yourself, even with the aid of a joystick-controlled robot —which suggests that tickling has something to do with social bonding. Beyond that, we have only a series of unsubstantiated theories.
Some believe tickling teaches infants to exert their will on others through vocalization. When a mother tickles her baby, he smiles and laughs—a highly desirable response for the mother, who reacts to the positive feedback by tickling harder. When the baby no longer enjoys the attention, he begins to fuss, causing the mother to stop. Through this process, the baby learns to control his mother's actions. If that's the case, then adult ticklishness might be the useless by-product of a trait that evolved for the benefit of infants. According to Nicholas Christenfeld of U.C.–San Diego, who studies the social context of tickling, gargalesis in mature humans might be "a kind of neuronal bellybutton."
Charles Darwin thought differently. In The Expressions of the Emotions in Man and Animals, he theorized that tickling was the basis for adult humor. Children learn to participate in shared laughter through tickling, and the behavior then transfers to more-abstract cues. According to Alan Fridlund, a psychologist at U.C. –Santa Barbara and author of a paper on the relationship between tickling and laughter, "the kinds of humor we have may be just mental equivalents of physical tickles."
Adolescent chimpanzees laugh frequently during rambunctious play, leading some to believe that tickling may have been the original primate dominance game—making a tickle fight between a congressman and his poorly paid underlings particularly apt. Laughter reassured the participants that the game would not proceed to violence. In fact, ape tickling more often leads to sex.
That brings us back to Eric Massa and Larry King. Can two adults tickle just for the fun of it, or is there something inherently sexual about tickling? Here, the nonhuman apes provide a mixed answer. While tickling juveniles sometimes proceed to have sex, it's hardly the rule. According to Marina Davila-Ross, the University of Portsmouth researcher with the temerity to tickle apes, adult orangutans seek out tickling from their human caretakers in zoos, approaching and exposing the soles of their feet or the napes of their necks. They can't possibly be expecting a roll in the hay to ensue.