First born sons have lots of responsibilities: being redeemed (Pidyon HaBen), fasting before Passover, and not losing their birthright to a deceptive younger brother.
Add one more to the list. Being smart.
A study in Norway has found that firstborn sons have higher IQs than younger brothers. But…
This study provides evidence that the relation between birth order and IQ score is dependent on the social rank in the family and not birth order as such…. Their studies confirmed what many scientists had suspected for more than a century — that firstborns have an edge. (MORE)
Oddly enough, Genesis revealed this millenia ago.