Massive study: Birth order has no meaningful effect on personality or IQ.

http://news.illinois.edu/news/15/0716birth_order_brentroberts.html

University of Illinois psychology professor Brent Roberts and postdoctoral researcher Rodica Damian conducted the largest study yet of birth order and personality. They found no meaningful relationship between birth order and personality or IQ.


PAPER: The associations of birth order with personality and intelligence in a representative sample of U.S. high school students.

http://www.sciencedirect.com/science/article/pii/S0092656615000525

Please see also:
Birth order does not have enduring effects on personality!
http://onlinedatingsoundbarrier.blogspot.com.ar/2013/11/birth-order-does-not-have-enduring.html