Is your oldest brother smarter? Study says so
By Benedict Carey - New York Times
The oldest children in families tend to develop higher IQs than their younger siblings, researchers are reporting in a large study that could settle more than 50 years of scientific debate about the relationship between IQ and birth order.
The average difference in IQ was slight - three points higher -- but significant, the researchers said. And the results made it clear that it was due to family dynamics, not to biological factors. Researchers have long had evidence that first-borns tend to be more dutiful and cautious than their siblings, and some previous studies found significant IQ differences. But critics said those reports were not conclusive, because they didn’t consider the vast differences in up-bringing between separate families.
Researchers said Thursday [June 21, 2007] that the results – being published today in separate papers in two journals, Science and Intelligence -- would lead to more intensive study into the family dynamics behind such differences, which are not yet well understood.
In the study, Norwegian epidemiologists analyzed data on birth order, health status and IQ scores of 241,310 18- and 19-year-old men born from 1967 to 1976, using military records. Because gender has little effect on IQ scores, the results almost certainly apply to females as well, said Dr. Petter Kristensen, an epidemiologist at the University of Oslo and the lead author of the Science study. (Photo: The Brothers Rolfsrud -- This recent photograph is illustrative of the relative intelligence of siblings as revealed by the Norwegian study. Virgil, left, is the youngest; Stan, center, the oldest; Stephen, in dunce cap, the middle child. Ironically, Virgil and Stephen distinguished themselves with advanced degrees, in econonics and law. Stan did not, although he once received a certificate of appreciation from Richard M. Nixon for serving in the Army and from the Canadian Government for helping to extinguish a forest fire.)
