Steve Connor in The Independent:
The difficult middle child, the spoilt only child, the wayward baby; few of us escape being labelled according to some sort of sibling stereotype. But what, really, are we to believe about the role our position in the family plays in determining our personality? Are the stereotypes true – or is the psychology of birth order just a load of hokum?
New research undertaken by scientists at the University of Oslo would suggest that there is, in fact, a good deal of truth in our family folklore. Using the IQ tests taken from the military records of 241,310 Norwegian conscripts, the scientists have found that eldest siblings are, on average, significantly “more intelligent” than second-borns. It may not seem like much, but 2.3 points on the IQ scale – the average difference between first and second siblings – could be enough to determine whether or not someone gets into a good college.
But what is equally intriguing about this study, which carries the kudos of having being published in the peer-review journal Science, is the way the scientists have tried to tease apart the possible reasons for this difference. Is it something that begins with gestation in the womb, or is it just the way siblings are reared within the family?