I been saying it all along...

Firstborn sons have higher IQs, Norway study finds

By Ishani Ganguli2 hours, 13 minutes ago

Firstborn sons have higher IQs than their younger brothers, and their social status within the family may explain why, researchers reported on Thursday.

A study that used military draft records for more than 240,000 Norwegian men found that firstborns had an edge of 2.3 IQ points on their next oldest brothers, who in turn beat brothers born third by 1.1 points on average.

Men who had been raised as the eldest, whether they were born first, second, or third, had IQs to match their first-born peers. The same was true for those raised or born second, Petter Kristensen and colleagues at the University of Oslo report in the journals Science and Intelligence.

"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's team wrote in Science.

Their studies confirmed what many scientists had suspected for more than a century -- that firstborns have an edge.

But attempts to prove the effect have been disputed, in part because the circumstances of each family are different.

To compensate for this, Kristensen's team studied brothers raised in the same families.

And some scientists argue that birth order IQ differences arise in the womb, while others point to family interactions.