Firstborn children are the cleverest
New Scientist: "Firstborn children score significantly higher in IQ tests than their younger siblings,".
"Parents might be able to boost the IQs of younger siblings by scheduling in more individual time with them" - well; no shit Sherlock! If I had all the time I had with my first daughter with my other kids - they would of course be different. But time spent with an individual child is inversley proportional to number of kids! ie more kids = less time with each!