A new study on birth order has found that first-born children are more intelligent than their siblings.
Researchers at Vrije University, Amsterdam, studied 650 children testing their IQs thrice, at the ages of 5, 12, and 18 in their lives.
The findings led them to conclude that the oldest child is more likely to have a higher IQ, and the youngest likely to have the lowest. The pattern was seen both in boys and girls.
Dorret Boomsma one of the authors who will publish the work in the journal Intelligence
, said: "The highest IQ scores were in children without any older siblings, followed by children with one older sibling."
"Children with two or more older siblings obtained the lowest score," he added.
The research does not spell out why exactly this occurs, but it is believed that the level of attention parents lavish on first-borns boosts their intellectual development.
The Amsterdam research is the latest in the line of researches that found birth order to have a fundamental effect on intelligence. Their findings add to earlier studies where it appeared that birth order could affect other factors such as personality and achievement.
Previous studies have shown that although first-born children are more likely to be academically successful and win Nobel Prizes, they are less likely to be " radical or pioneering." Charles Darwin, for instance, was the fifth child of six.
Another study on birth order shows the youngest is the most favored though the oldest may be the brightest.
University of California studied 2000 families and found first-borns are achievers, who are "dominant, religious, conscientious and neurotic."
Those born in the middle are "rebellious, less religious, impulsive and open to new experiences."
Those born last are "agreeable, sociable and creative." The last-born was found to be usually the favorite.