Claim: Firstborn children tend to have higher IQ’s than their younger siblings.
Is this true or false, and what is the source of this claim?
It’s true.
Results of several studies were published in 2007 in which researchers found firstborns to have a three-point higher IQ on average than their next youngest sibling. The factors leading to this slight intellectual advantage appear to be due to family dynamics and not biological.
While it isn’t clear why older children hold this slight edge, one theory holds that the child has its parents’ undivided attention in the earliest years.
The study compared IQ scores and birth order among over 200,000 18- and 19-year-olds born from 1967 to 1976. The result is that the eldest children averaged IQ’s of 103.2, while second-born children averaged 100.3 and thirdborns scored 99.0.
Source
Research Finds Firstborns Gain the Higher I.Q. (Benedict Carey, The New York Times: June 22, 2007)
