By Jon Lackman
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?"
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