Birth order and IQ

You'll often see twins and other sibling groups taking a certain pride in being born first. This isn't the only thing birth order affects. According to a new study published in the Proceedings of the National Academy of Sciences, kids' IQs may also be related to when they were born in relation to their brothers and sisters. 

The study
Researchers compiled data from the U.S., Great Britain and Germany, with a total of 20,186 study participants across the three areas. The people involved in the group were siblings who lived together or with multiple families. Study authors took the "nature versus nurture" approach to see if even siblings who live apart from one another still exhibit the same personality and IQ tendencies as those who live in the same home. The scientists claim they saw similar results to conclusions from past studies: First-born children are slightly more intelligent than their younger brothers and sisters. 

While the study found a link between birth order and IQ, researchers also wanted to note if this time-related fact affected a child's likelihood to be extroverted, agreeable, conscientious, imaginative and emotionally stable. There was no correlation between when participants were born in relation to their siblings and whether they exhibited the above traits. The researchers concluded that birth order doesn't affect personality traits, but may alter intellect.

Study author Julia Rohrer told Time magazine she was surprised the results were so clear. She added that some children will simply take on the stereotyped role of their birth order. The eldest may act more responsibly, for example, while the youngest could act out and not take life too seriously. Rohrer also mentioned that older children may take it upon themselves to tutor their younger siblings, therefore, boosting their own intelligence while also helping their younger brothers and sisters. 

According to The New York Times, a previous study found the average IQ difference between the eldest child and the second eldest was just three points. While it doesn't sound like a huge advantage, those points may be the difference between letter grades or even an average versus gifted child. Plus, those three points were an average that occurred in many families participating in the study, as not every set of siblings exhibited the same findings.