Kenneth Wexler never expected to provide a definitive way of pinpointing a language disorder that afflicts hundreds of thousands of kids–and by so doing, perhaps improve the outlook for many of these youngsters.

Long involved in the study of language and the mind, Wexler, a professor with appointments in both brain and cognitive sciences and in linguistics and philosophy, made his mark with studies of how young kids learn to communicate.

It’s complex work, which requires him to draw on his math background–he majored in the subject as a University of Pennsylvania undergraduate–as well as his knowledge of psychology and linguistics. But it has led to key discoveries, among them the fact that tots as young as a year-and-a-half understand grammar basics to a far greater extent than previously recognized.

Wexler’s studies have also earned him recognition in academic circles. With two other leading MIT faculty members, Noam Chomsky and Steven Pinker, Wexler was labeled one of the “giant figures” of psycholinguistics in a 1994 article on his work.

Since Wexler’s mainly a theorist, his key focus is how children in general accomplish the complex task of learning language. Until seven years ago, he’d never looked into language problems that afflict particular groups of kids.

In 1991, though, an expert in such problems, Mabel Rice of the University of Kansas, approached Wexler after hearing him give a talk. Rice’s special interest is a condition called Specific Language impairment (SLI).

“She felt that people didn’t know how to connect SLI to current views on normal language development, and wondered if I could help clarify the issue,” says Wexler. So, Rice came to MIT for a semester, and the pair went to work.

Delayed development

At the time, it was clear kids with this deficiency lag in producing grammatical sentences. Still, Wexler admits he harbored some doubts about the collaboration’s prospects. “It was a stab in the dark,” he notes. “I had no idea what we might find out about impaired kids.”

After laborious studies comparing the speech of impaired and unaffected preschoolers, though, the researchers pinned down SLI’s exact nature. “The amazing thing,” notes Wexler, “is that SLI turned out to be a greatly delayed version of what I’d already shown happens in normal language development.” Now, the two are using this knowledge to create the first-ever screening test for the condition.

Specific Language Impairment shows up as early as age two. Initially, the kids affected may exhibit varied language problems: They have smaller vocabularies than their peers, use shorter sentences, and make errors like saying “He walking” instead of “He is walking.”

Preschoolers with such problems–and SLI’s not the only source of them–can run into social difficulties, says Tim Brackenbury, a speech-language pathologist associated with Mabel Rice who works with language-impaired youngsters. For example, they tend to be last picked when kids choose participants for games or contests.

“Three- and four-year-olds are pretty keen as to who’s a good communicator,” says Brackenbury. “Even the SLI kids won’t pick other SLI kids as their preferred playmates.”

In time, the vocabularies of SLI-affected youngsters improve, and their sentences get longer. Eventually, their most significant problem is an inability to get certain verb forms right.

Since the condition can be difficult for an untrained observer to spot, though, the affected children sometimes miss out on well-targeted therapy. “They get labeled as learning disabled, but they’re really not,” says Brackenbury. “If you look at their performance on the non-verbal parts of IQ tests, they track right with their peers.”

Problems in school

Therapies that attack the particular language deficiencies of SLI help. But children who don’t receive such aid may get well up into their elementary school years, and perhaps beyond, without making much headway – and may face academic and social problems as a result.

“If an eight- or nine-year-old says things like ‘I eating ice cream,’ notes Wexler, “it’s natural for their teachers and peers to assume they’re quite immature.”

Collaborating with Kansas’ Rice, though, Wexler showed that an inability to get verb tenses right is the hallmark of SLI. The test that Rice and Wexler are working on, to be published in about two years, will let teachers and other professionals make definitive diagnoses of SLI in kids who are still at a relatively young age. It should thus improve the affected youngsters’ chances of getting treatment that directly addresses their problems.

Meanwhile, Wexler has embarked on a new study. Having shown SLI runs in families, he’s working with a University of Iowa group to find the genetic defect, and maybe even the particular gene, or genes, underlying the condition.

It’s a unique effort, and Wexler admits to being a bit awed by its implications. “If we succeed,” he says, “it would be the first time that anyone had discovered how an element of language–of the universal grammar we all carry in our heads–is expressed in the human genome.”

At the same time, he’s thinking ahead to when his studies of SLI begin to yield benefits for the kids affected. Though still mainly a theorist, he’s excited by the idea his work may have such payoffs.

“I do science in the expectation it will someday be useful,” he notes. “Given the field I’m in, though, I always thought it would be a long time before that happened.

“I’ve been surprised at the speed with which things seem to be moving,” he adds, “and I’d be really pleased if our work turns out to actually help significant numbers of kids.”