Twins and Singletons Evenly Matched Academically
Ninth-grade test scores comparable although twins weigh slightly less at birth
THURSDAY, Oct. 5 (HealthDay News) -- Although previous studies have suggested otherwise, twins have academic test scores similar to singletons when tested in the ninth grade, researchers report in the Sept. 29 Online First edition of BMJ.
Kaare Christensen, M.D., Ph.D., of the University of Southern Denmark in Odense, and colleagues compared ninth-grade test scores, birth weight and other factors in 3,411 twins and 7,796 singletons born between 1986 and 1988 in Denmark.
The researchers found that both groups tested normally in ninth grade, with a mean test score of 8.02 for both groups, and a 1.05 standard deviation for twins versus 1.06 for singletons. Newborn twins generally weighed almost a kilogram (908 grams) less than singletons.
The similarity in test scores held firm after researchers adjusted for factors such as parents' age, and the gestational age and weight of newborns. Although the researchers found a significant link between birth weight and test scores, the standard deviation in test scores was only 0.06 to 0.12 for each additional kilogram at birth.
"Although older cohorts of twins have been found to have lower mean IQ scores than singletons, twins in recent Danish cohorts show similar academic performance in adolescence to that of singletons," the authors write.