When I was 6, my 2-year-old brother started speaking, but in a language of his own devising. I was eager to enlist him in games (my favorite: "Slave") and so quickly mastered his lexicon. My parents never managed to, despite their advanced degrees, and so our dinner table came to resemble a Camp David summit—two sides forced to use a translator to argue for their conflicting philosophies of life. "Eat peas!" "Throw peas!" "Feet on the floor!" "Feet in the tuna casserole!"
Siblings, and especially twins, have been inventing private languages since time immemorial, to little fanfare, but recently such ingenuity has captured the public's imagination. This spring, a YouTube video of jabbering twins went viral, and even made it into the New York Times' Well blog. The Washington Post recently celebrated a new play that revolves around a similar pair of girls and their "secret twin-speak." Scientists, meanwhile, have spent the last few decades quietly building up a body of research into what they call "cryptophasia" or "twin language," and they are of two minds about it. They find it fascinating, as a window onto the origins of human language, but they also worry that it hampers children's development.
Twins are especially likely to maintain an invented language because they spend so much time together and are on the same developmental schedule. They imitate and reinforce each other's early inventions, weakening each other's incentive to learn the mother tongue. They spend less time communicating with parents and other adults, on average, than do nontwins, because they always have a ready playmate and because their parents are especially busy. Twin parents must change more diapers, sleep less, earn more, and parry the brilliant questions forever tripping off other parents' tongues like, "Is it true that twins only have half a brain each?"
I called my mother recently, eager to learn more about my brother's language. "Oh, he just had a speech impediment," she said. That's not unusual, I found out. When scientists first started researching cryptophasic kids, they too were disappointed to discover that kids mostly just mispronounced words or made inside references. For instance, their word for pasta might be "oliga" if they'd first had it at Olive Garden. As Queensland University of Technology psychologist Karen Thorpe explained to me by email, it's like "the conversations between married couples where words are invented and abbreviated or restricted codes are used because full explanations are redundant." In some cases, there's no secret language at all, just the appearance of one. Those YouTube twins? Not cryptophasic, just really good at pretending to understand each other.
In rare cases, however, children do develop an entire language of their own, and amazingly, all full-blown twin languages spontaneously develop the same structure, regardless of the language spoken at home. Aarhus University linguist Peter Bakker told me that twin-language structure is unlike that of any established language, and its syntax doesn't simply reflect the usual mistakes made by children. (Deaf children not taught sign language who invent their own also use this structure, by the way.) This "gives us a potential insight into the nature of language," Bakker said, into mankind's "first language," now lost to history.
Twin languages are simple, just as simple as necessary, one might say. For one, they freely mix subjects, verbs, and objects, putting the most important item first in any context. In an Estonian study a child said, in his private language, "Again I foyer toward write come." (Estonian grammar would have dictated, "I come again to the foyer to write.") Negation appears at the sentence's beginning or end, regardless of where it appears in the native language. Thus one Swiss child said, "Bobby, here drive no!" instead of, "Bobby, don't drive here!" Verbs aren't conjugated. There's no way to locate things or events in time and space. And finally, twin languages almost never use pronouns, just proper names. Language can get simpler than this, but not much. (Bakker is a fan of the satirical 1982 film On Top of the Whale, in which scientists discover a primitive tribe whose language consists of only one phrase, which they apply to every object they come across. Rough translation: "It will be mine!")
If language originated between just two people, it might well have looked like this: The seemingly universal twin-language structure is blissfully easy to use in one-on-one conversation. However, that first language would have had to evolve quickly to be useful to a larger community. Societies need "unambiguous ways to distinguish between subject and object," Bakker says. "In the twin situation these can be dispensed with, but not in languages in which it is necessary to refer to events outside the direct situation." So it's hard to say for sure if twin language really does offer us that hoped-for picture of man's first sentence. ("Voulez-vous coucher avec moi, ce soir?" is my guess.)
Linguist Bernard Comrie at UC-Santa Barbara cautions that research into the birth of language is still in its infancy. "First we were told that creole languages would provide us with insight into 'first language,' then when that didn't pan out interest shifted to deaf sign language (also with mixed results)—I guess twin language will be the next thing," he wrote me. Twin language is particularly difficult to test because children give it up quickly, except when they are very isolated. And you can't just isolate kids on purpose—not anymore, anyway. Gone are the days when the pharaoh Psammetichus I could send two infants off to be raised by goats, or the Holy Roman Emperor Frederick II could forbid children's caregivers from speaking to them.