NEW YORK -- Left-handedness, allergies and nearsightedness may go hand in hand with great intelligence, a survey of gifted children indicates.
As part of the John Hopkins Talent Search program, researchers evaluated biological characteristics of 400 gifted 12-year-olds whose abilities were assessed with Scholastic Aptitude Tests (SAT), the pre-college tests usually taken by high school students.
Six out of every 10 of the children were nearsighted, which is four times as many as would be expected, Camilla Benbow, associate research scientist in psychology at Johns Hopkins University in Baltimore, Md., reported Thursday at a neurobiology conference.
The verbally gifted children tended to be more myopic than those gifted in math.
Sixteen percent of the children were left-handed, twice as many as would be expected. Two-thirds of the children had allergies or another condition related to an immune abnormality, again double the expected rate, Benbow said.
'It's just pointing to possible biological correlates to high abilities,' she said in an interview. 'But environment is also very important.'
The parents and siblings were less likely than the children themselves to have these traits, she added.
Of the 400 students, 292 were 'math-talented,' scoring at least 700 out of a possible 800 in the mathematics section of the test, while 165 were considered 'verbally-talented.' Some students were skilled in both areas.
An estimated one in 10,000 children is that smart.
In the verbally gifted group, boys and girls were about equal in number, but only 20 girls got especially high scores in the mathematics test, she said.
Myopia, or nearsightedness, and left-handedness have been linked before to higher intelligence.
According to one theory, high levels of testosterone, a hormone, in the developing brain of the fetus can slow growth in the left side of the brain and affect the development of the thymus gland, which influences the immune system, Benbow explained.
As a result, the right side of the brain becomes the stronger, more dominant side and could account for an increase in left-handedness and mathematical abilities, which are supposed to be influenced by that side of the brain.
The allergies and other autoimmune disorders may represent shortfalls in development of the immune system.