Firstborn Children have a higher IQ

A recently released study of 240,000 men, showed that firstborn children on average have a higher IQ than their siblings. Their IQ is 2 to 4 points higher than their siblings. The study showed that being born first was not necessary. The only criteria needed was to hold the oldest position in the family. So a middle child who's older brother had died, would consistently have an IQ comparable to that of an oldest child. So the phenomenon clearly has a social, rather than a genetic cause. But being an oldest myself, it is still pretty cool. I can't wait to tell my brothers that it has been scientifically proven that I, being an oldest, am smarter than they are. LOL

Via Scientific American: Intelligence Fostered by Firstborn Treatment