Since 1977, deaf children in Nicaragua have been creating an increasingly sophisticated system of hand signals to communicate. Successive generations of children have, on their own, introduced new features that are found only in true languages, according to a report published today in Science. "They're creating language out of gesture," says lead author Ann Senghas of Barnard College.

Many linguists regard Nicaraguan Sign Language, or NSL, as an important test case, because the language developed almost in isolation, and the first "speakers" are still alive. Until the government opened a school for the deaf in 1977, deaf children in Nicaragua had been socially isolated. The students had little exposure to written language, and the school did not teach signing. Instead, the children invented the language largely on their own, with each generation building on what they learned from preceding students.

True languages get much of their power by breaking complex ideas into small pieces, such as words, which can then be rearranged to form innumerable new ideas. "It's like building with bricks rather than building with clay," Senghas explains. To look for this feature in NSL, the researchers played a cartoon showing a cat wobbling down a hill after eating a bowling ball. When asked to describe the motion, Spanish speakers who can hear often augment their verbal description with a gesture that combines the ideas of "wobbling" and "down" in a single motion (top). Deaf students from the early years of the school use a similar gesture, which is a direct analog of the distinctive motion. In contrast, later generations of students separate the ideas of "wobbling" and "down" into distinct signs (bottom). Although the separation actually weakens the description, it is an important feature of abstract language, the researchers note.

Other research has shown that sign language uses some of the same brain machinery that hearing people use for speech. The new results strengthen the idea that this machinery is predisposed to abstract language even without being taught. "The fundamentals of language, Senghas remarks, can arise just from the way that children learn language." --Don Monroe