Dyslexia: new twist on 'word blindness.'

Anew scientific study challenges the traditional view of dyslexia as an all-or-nothing phenomenon. Instead, the new data suggest that this reading disorder occurs in a spectrum of cases ranging from mild to severe.

"Dyslexia is currently envisioned as a discrete entity--either you have it or you don't," says Sally E. Shaywitz, a pediatrician with the Yale University School of Medicine in New Haven, Conn. But data collected by Shaywitz and her colleagues indicate that "dyslexia is much more like hypertension, occurring along a continuum with gradations or degrees," she told SCIENCE NEWS.

Dyslexia, also known as "word blindness," is broadly defined as the failure to read at expected levels. Dyslexic children exhibit normal intelligence and often perform well in other academic areas such as mathematics. Yet these children have difficulty translating strings of letters into verbal utterances. Thus, a dyslexic child will repeatedly stumble over common words in a frustrating attempt to read a simple passage.

To find out more about how children learn to read, Shaywitz and her colleagues designed a project called the Connecticut Longitudinal Study. The researchers randomly selected 24 kindergarten classes during the 1983-1984 school year and then kept track of these youngsters from first through sixth grade. Kids took intelligence tests in grades 1, 3 and 5 and reading achievement tests yearly. The diagnosis of dyslexia was reserved for children whose reading ability fell far below the level predicted from their intelligence test scores.

Using statistical techniques, the researchers found that variations in discrepancy scores -- a measure that takes into account reading achievement and intelligence -- followed a bell-shaped curve. Scores for dyslexic children tended to appear toward the end of the curve, but there was no natural cutoff point separating dyslexic children from those with normal reading skills, Shaywitz says.

A well-known study reported in 1970 had suggested that discrepancy scores for dyxlexic children appeared as a hump at the end of the curve -- quite separate from the rest of the data points, Shaywitz notes.

Instead of depicting dyxlexia as a fixed condition that doesn't change over time, the new data indicate that a child's reading ability can vary widely, especially during the arly school years. For example, only seven of the 25 children classified as dyslexic in first grade got the same label again in the third grade. And fewer than half of the third graders diagnosed as dyslexic kept that label when retested in the fifth grade. Of the first graders diagnosed with dyslexia, only one in six still had that label by the time they reached the sixth grade.

Children who test adequately one year but fall behind the next may escape the notice of educators, Shaywitz says, noting that many schools offer special reading classes only to children who test poorly at one specific point in time.

Shaywitz believes that system is flawed. "It may be that because of administrative and budgetary constraints, school administrators need to establish a cutoff point for determining who is eligible for special help," she says. "But people will have to realize that such a cutpoint is arbitrary and that children who fall on the other side of it may still require and benefit from special help."

The current system may not flag children with very mild learning disabilities, adds Peter B. Rosenberger, a pediatric neurologist with Massachusetts General Hospital in Boston.

"If you have a bright kid who is only reading at grade level and his teacher says there's nothing wrong with him, this study offers evidence that you should be concerned," Rosenberger contends. Very intelligent children often read well above their grade level, he notes.

While a mild difficulty with words may pose no particular difficulties in the third grade, sluggish reading can trip up students later, especially if they are collegebound, says Rosenberger, whose editorial on the Shaywitz study appears along with the research report in the Jan. 16 NEW ENGLAND JOURNAL OF MEDICINE. Many dyslexic children who receive coaching overcome their difficulties, he adds.

At the same time, the disorder can be tricky to diagnose -- or even define. Although educators look for a gap between reading ability and IQ score, such a gap may not always indicate dyxlexia, says Reid Lyon of the National Institute of Child Health and Human Development in Bethesda, Md., which funded the Shaywitz study. In some cases, intelligent youngsters may not excel in reading--just as some bright people can't sing or hit a tennis ball well, Lyon notes.