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Thursday, Sept. 30, 2004

NATURAL SELECTIONS

SPEAKING IN SIGNS

Deaf school phenomenon points to innate language origins


So there's this deaf American visiting Russia, and he's thirsty. Using American Sign Language, he says to his deaf-guide, "I really want a soda." But in Russian Sign Language, the gestures he used correspond to, "I really want to have sex." Guessing at some linguistic problem, the Russian guide diplomatically ignores the American's request and signs back with some small talk: "I'm from Moscow." Unfortunately, the RSL for "I'm from Moscow" corresponds to "I menstruate" in ASL.

The anecdote is probably apocryphal, but it illustrates an important point about sign languages. They are equivalent to spoken languages right down to the capacity for comic misunderstanding. And like spoken languages, the evidence is mounting that sign language develops through innate rather than culturally transmitted means. In other words, there is a language organ in the brain and we are all born with hard-wired rules of grammar.

The most compelling evidence for this comes from a school in Managua, Nicaragua.

In 1977, a school for the deaf opened in Managua, and 50 students enrolled; by 1981 there were 200 students, all able to chat using sign language. What's remarkable about the story is that no one taught them to sign. The first students simply started gesturing among themselves, and the system developed into what is now a true language, with grammar and rules of its own.

The Nicaraguan school is studied by Ann Senghas of the department of psychology at Columbia University in New York, who has been visiting once a year since 1990. Senghas and colleagues examined the "discreteness" of the children's sign language.

Discreteness is a feature of true languages, whereby information is packaged into separate elements that can be put together according to various rules. The separate elements are words (split into nouns and verbs) and the rules are grammar.

For example, Senghas said, in the expression "rolling down the hill," one word (rolling) conveys the type of movement, while another (down) conveys the direction. The phrase meets the criterion of coming from a developed language because the idea of continuous movement is broken into separate words.

However, in basic gesturing, the phrase "rolling down a hill" is usually represented by a single, unbroken movement of the hand, such as a circular motion along a downward path.

Senghas and her colleagues looked at how deaf individuals of different ages at the Managua school described the phrase, and compared it with hearing individuals.

The signing of the oldest group looked much like the simple gestures produced by the hearing group as they spoke, combining movement type and direction in a single hand motion. But the younger students separated the movement type and direction into different signs, as is done in spoken language. "So what they're doing looks very language-like and does not look gesture-like, even though they're taking gestures to make the language. And that tells me there's something really core about that drive," Senghas said.

A paper on her work was published earlier this month in the journal Science. The work shows that even without being taught, children automatically seek out rules of language in order to communicate. Like spoken languages, a pidgin form of gesturing can develop into true language in a generation. And Senghas' research adds weight to the idea that the origin of language itself lies in gesture rather than speech.

How this may occur is described by the British science writer Matt Ridley in his book "Nature via Nurture" (Fourth Estate, 2003). Around 5 million years ago, he notes, when our ancestors first stood upright on two feet, their front limbs were free to carry things, to wield tools and to gesture. And apes live in social groups. Grooming -- an activity that requires careful motor control of the hands -- is important for social bonding, and could easily give rise to a gesture-based form of communication.

This sort of evidence is suggestive rather than conclusive, but it does make a nice story. It's also worth remembering that the changes to the larynx and chest that are necessary for speech happened much later in our evolutionary history than the anatomical changes that gave early humans elaborate manual dexterity.

In any event, in the case of the Managua children, simple gesturing has developed into a true language in a generation. "We're seeing evolution in action, but what's evolving here isn't an organism. It's a language system," Senghas said.

When we conventionally think about evolution, we think of things like white moths living in trees covered in soot. When a gene mutates that causes some moths to grow dark wings, it is favored by natural selection because the moths are camouflaged and less likely to be eaten by predators.

But what Senghas is referring to is not the spread of genes in moths, but the spread of ideas in brains.

This is Oxford University biologist Richard Dawkins' concept of the meme.

Just as genes that have a positive effect become more common, so gestures that are useful and easily understood become more common. The process is the same as that governing the spread of genes: natural selection.

Children's brains make the ideal environment for natural selection to work on. All that is needed is social interaction, and language will flourish.

"Kids have their radar out from the beginning; they're looking for language-like information in the world," Senghas said. "And they're ready to process that information in a specific way. You don't need to teach children language any more than you need to teach them to walk."

A book of Natural Selections columns translated into Japanese, "Nou to sekkusu no seibutsugaku (Evolution, Sex and the Brain)," is published by Shinchosha. Rowan Hooper is a biologist at Trinity College, Dublin. He welcomes readers' questions and comments at rowan.hooper@tcd.ie


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