The left hand of math and verbal talent.

Scientist at Johns Hopkins University in Baltimore say that children who possess extremely high levels of mathematical or verbal ability tend, far more often than children of normal ability, to be left-handed, nearsighted and suffering from asthma or other allergies.

"We've identified some biological correlates of intelligence," says study director Camilla Benbow, who stresses that these factors have not been shown to cause higher intelligence. "We view our [mathematically and verbally] precocious kids as unpredictable products of [genes] and environments."

From a national sample of over 100,000 children between 12 and 13 years of age, Benbow and colleague Julian Stanley identified and studied 292 youngsters who scored at least 700 out of 800 on the mathematical reasoning section of the Scholastic aptitude Test (SAT) and 165 individuals wno scored at least 630 out of 800 on the verbal section on the SAT (there was some overlap between the two groups). The tests are designed to be taken by high school seniors.

Over 20 percent of the children with the top scores are left-handed or ambidextrous, reported Benbow at a conference on the "Neurobiology of intellectual Giftedness" in New York City last week. This is twice the rate of left-handedness found among the general population of 12- to 13-year-olds. Youngster with the highest SAT scores also are twice as likely to have allergies and four times as likely to be myopic, adds Benbow. Eighty percent of the "precocious" children have at least one of these three characteristics.

The data also support previous studies by the Jopkins researchers that found boys to be superior to girls in mathematical skills (SN: 8/28/82, p 136). For every 13 boys who scored at east 700 on the math SAT, only one girl achieved a comparable score. The survey measured boys' and girls' attitudes toward a mathematics and uncovered no differnces, says Benbow. Several environmental factors that may contribute to sex difference on math scores also did not appear to be significant in this sample, she observes. There was no difference between the sexes on verbal scores.

Benbow acknowledges that the topscoring children often have intelligent, professional parents who encourage their intellectual potential. Several scientists at the conference said that the youngsters' cognitive and social development should be more closely examined

The analysis of mathematically and verbally precocious youths stems in part from a theory proposed by the late Norman Geschwind, a Harvard University neurologist. He obserbed that left-handed people apear to have more immune disorders, migraine headages and learning disabilities. Geschwind believed that if a fetus is highly sensitive ti the male hormone testosterone, or if it is exposed to high levels of the substance, the development of the left brain hemisphere--which is more involved in verbal ability -- is slowed. To take up the slack, the right hemisphere -- which has more control over spatial and mathematical ability -- grows larger and left-handedness becomes a more likely consequence.

Some scientists say that hemispheric function in the brain is not as clear-cut as Geschwind suggested. But Benbow suggests that since mathematically and verbally talented individuals shared the same biological characteristics, they may have a more balanced hemispheric distribution of these abilities than is found among children of average intelligence.

Benbow's interpretation is open to debate, but there is clearly a high incidence of left-handedness, allergies and myopia among mathematically and verbally talented children says Robert N. Sawyer, director of a program at duke University in Durham, N.C., that uses SAT scores to identify precocious seventh graders. Unfortunately, he notes, there are few biological or psychological data on children with average SAT scores -- a lack that muddies any comparisons between "normal" and "gifted" students.