Language without Rules; a Curious Speech Disorder Raises Questions about the Genetics of Grammar
Bower, Bruce, Science News
Media reports in 1992 announced the discovery of a gene that regulates the ability to learn grammar. Editorial writers and humorists immediately pounced on the claim. Scientists will promote genes for spelling and neatness next, intoned one incredulous commentator. Pity the throngs of grammar-gene-deprived teenagers, who consider "bummer" and "awesome" complete sentences, another wrote.
But an inconvenient fact lurked behind these jibes: Scientists had not wrung a "grammar gene" out of microscopic strands of DNA. They had, in fact, tracked a speech disorder through three generations of the "K" family and suggested that a single gene somehow disrupts the ability of these intelligent, well-adjusted people to converse normally. The hypothetical gene, according to researchers, may orchestrate proteins that either specifically target or inadvertently jam brain circuits that endow speech with grammatical structure.
Affected K family members -- 16 of 30 children and adults living in England -- knit words into an awkward, confusing patchwork. For example: "I walked down the road" or "Carol is cry in the church." When telling a story, they nearly always allude to others with nouns rather than pronouns (for instance, referring to "the man" rather than to "he" or "him").
Grammatical rules taken for granted even by preschoolers prove foreign to the 16 K offspring; therefore, after seeing a picture of an imaginary animal called a "wug," they do not know that "wugs" referst to more than one "wugs."
Language-impaired individuals in the K clan often seems as if they speak English as a second language. Words come slowly, often after careful planning of what to say. They encourage others to help them complete sentences and avoid situations that force them to speak.
"This disorder appears to involve a genetic factor or factors," says linguist Myrna L. Gopnik of McGill University in Montreal, who directs the K family study. "For the first time, we have a chance to get directive evidence about the biological basis of language acquisition."
Efforts to decode the inner workings of this derailed discourse, known as specific language impairment (SLI), or developmental dysphasia, have intensified in recent years and attracted psychologists, linguists, speech-language pathologists, and educators. Although many of them view SLI as at least partly inherited, a widely accepted definition of its core features remains elusive.
Clinicians diagnose SLI when children exhibit difficulty speaking their native language in the absence of any apparent cause -- low intelligence, brain damage, hearing defects, emotional problems, or lack of exposure to adult talkers.
Some theorists see SLI as a broad syndrome encompassing problemsm in grammar, language learning, and reading. Others posit a narrower disturbance of either the ability to construct basic grammatical rules or to distinguish key speech sounds. Another question involves whether children displaying SLI learn to speak using strategies dictated by their condition or acquire language just as other children do, but at an agonizing slow pace.
Published descriptions of SLI, originally called congenital aphasia, appeared as early as 1872, points out J. Bruce Tomblin, a speech-language pathologist at the University of Iowa in Iowa City. But systematic inquiry into the nature and causes of the condition emerged only in the past 20 years, he says.
SLI may afflict as many as 1 in 20 children and about twice as many boys as girls, Tomblin told the American Association for the Advancement of Science (AAAS) annual meeting in February. He bases these estimates on language testing of 1,300 Midwest public school kindergartners.
As the K family illustrates, SLI usually persists into adulthood, Tomblin adds. In a study of 35 young adults with documented SLI in childhood, all displayed marked language problems compared with same-age controls who encountered no problems in learning to speak, he reports. …