I have just discovered a profoundly human, evolutionarily crucial fact about the new baby in our house: He likes to be tickled.
This isn’t a joke. For centuries, the deepest of thinkers—Aristotle, Darwin, Shylock—have puzzled over this silliest of human acts. Robert R. Provine, a neuroscientist at the University of Maryland at Baltimore County, is their heir, and according to his new book, Curious Behavior, Shylock was on to something. Tickling is not an inexplicable physical tic. It’s central to who we are—and how we became who we are.
Provine first began researching tickling when someone came up to him before a talk on laughter—he’s an expert on the subject—and said she hoped he wasn’t studying tickling. She hated tickling. So inevitably, he decided to study it: “Her revulsion was persuasive.” If she’s that annoyed by it, he thought, it must be important.
Its importance begins in infancy. “When people say they hate being tickled and there’s no reason for it, they forget that it’s one of the first avenues of communication between mothers and babies,” he says. “You have the mother and baby engaged in this kind of primal, neurologically programmed interaction.” Or the father: I tickle my son; he shrieks; I tickle him more; he shrieks more; I tickle him yet more; he starts wailing. I apologize.
In a sense, this is our first conversation—how we manage to talk with someone despite being preverbal. The content here is socioemotional, and as a form of social binding, it preceded the development of language, Provine says. Play with a toddler and you might end up recapitulating that developmental progression: before talking comes tickling. “If one wants to become friends with a young child,” as the neuroscientist Jaak Panksepp has written, “there is no easier way to negotiate the social terrain than by gently escalating tickle games.”
Tickle games are not unique to humans. They’re part of our mammalian heritage. “Tickle is what binds mammals together in rough-and-tumble play,” Provine says. Pick a mammal. Squirrels engage in play that looks a lot like tickling. So do—of all species—elephants. So do rats: In a sensational experiment a decade ago, Panksepp recorded the ultrasonic sounds, inaudible to the human ear, that rats make when tickled by an experimenter. The rats, in other words, seem to giggle when tickled.
But only chimpanzee and human mothers gaze deeply into the eyes of their infants—and then tickle them. In the wild, chimpanzee infants will bite their mothers, who respond by tickling; the infants then bite their mothers again, which provokes more tickling; and so on. It’s a social dance: Tickling is the way we and the chimps establish, without words, that we’re in this thing together.