According to a recent study, the first born child in a family tends to be the smartest. Then it tumbles down hill after that (sorry Andrea).
Researchers from the Universities of Leipzig and Mainz analyzed the data from 20,000 adults in the US, UK and Germany and found that the eldest sibling tended to have the highest IQ.
Julia Rohrer of Leipzig University offered this explanation on why the eldest sibling might gain cognitive advantages, “A first-born can ‘tutor’ their younger siblings, explaining how the world works and so on. Teaching other people has high cognitive demands – the children need to recall their own knowledge, structure it and think of a good way to explain it – which could be a boost to intelligence for some firstborns.”
They also think that a first born’s increased attention from new parents might also help explain this finding.
— Lisa Zellery (@Buzzlefeed) October 4, 2015