>>10847544They are smarter for obvious reasons.
A few that come to mind:
- first born are born to younger and more healthier parents thereby reducing probability of difficulties in child birth that can impact on IQ
- First born are paid more attention by parents during early crucial stages of development (0-3 years old) as they only have one child.
-First borne get more social interaction with parents which is known to boost IQ.
It makes sense that first horns would be smarter. Its optimal that birth occurs while the parents are still young and healthy. In caveman times no one was even having children after the age of 30 as most died young.