Firstborns likely to have higher IQ than younger siblings

What do Bill Clinton, Hillary Clinton, Jimmy Carter and J.K. Rowling have in common? All are firstborns.

And, as firstborns, they are likely to boast higher IQs than their younger siblings, according to Norwegian research.

Indeed, if you are the youngest in your family -- and you've always felt slighted -- you may have been on to something.

A study of more than 240,000 Norwegian men found that firstborns have an edge of 2.3 IQ points on their next oldest brothers, who in turn surpass brothers born third by 1.1 points on average. It may not sound like much, but those 2.3 points correlate to a 15-point difference in SAT scores.

Although the study involved only men, researchers said that the results would apply to women, as well.

Researcher Petter Kristensen at the National Institute of Occupational Health in Oslo and his colleagues found that the way parents treat their children has as much to do with the results as birth order itself.

For example, oldest children often are showered with more attention and are given more responsibility than their younger siblings.

"This study provides evidence that the relation between birth order and IQ score is dependent on the social rank in the family and not birth order as such," Kristensen said.

Advantages to being younger

Ben Dattner, a psychology professor at New York University who has studied birth order, said middle and youngest children also have their advantages.

The youngest tend to be creative and charming while middle children tend to be diplomatic and have closer friends than do their older and younger siblings.

Dattner noted that computer company founder Michael Dell is a middle child.

"Michael Dell's job has always been to sell to the middle man, so he may be in tune with how the middle man can get squeezed because he is indeed a middle child," he said.

Remember, though, that birth order analysis is only a starting point to explaining a person's personality, Dattner said.

"Sure, firstborns often are conscientious and thorough and they also can be dominant and authoritarian," he said. "But it's not going to be this way 100 percent of the time."

Richard Woolfson, a child psychologist in Glasgow, Scotland, agreed that firstborns tend to be the most intelligent of all children and to be the likeliest to achieve.

"They also tend to be serious-minded and in traditional professions like medicine, law and accountancy," he said. "However, not every firstborn is guaranteed to have such a personality.

"It's important for parents to treat each child as an individual and not as a product of a birth order," he said.