The oldest child in a family tends to have a higher IQ than their siblings. While this difference is not huge (about 3 IQ points) and is not true in every case, it brings up interesting questions about what causes the difference. Is the first-born exposed to a more favorable chemical environment in utero? Or does the older sibling experience a social environment after birth that leads to higher IQ?
In the most recent issue of Science, Norwegian researchers reported that IQ levels are actually dependent on social rank within the family. They found that when the 2nd-born was brought up as the oldest child due to the older sibling’s death, the resulting average IQ score increased to that of a first-born.
An important takeaway from this research is that IQ is not genetically or developmentally fixed at birth. While genes almost certainly play an important role in intelligence, we see that environment and lifestyle can change level of intelligence. Hint-hint, nudge: go get smart with the Lumosity exercises. Or…
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Simple explanation: the oldest child doesn’t have any bigger siblings to whack them on the head!
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