Numerous studies have been done on siblings and twins who were raised separately. The IQ correlation between hereditary siblings is strong, that between twins

Numerous studies have been done on siblings and twins who were raised separately. The IQ correlation between hereditary siblings is strong, that between twins is overwhelmingly strong and that between adopted siblings is almost non-existent past adolescence. http://en.wikipedia.org/wiki/Inheritance_of_intelligence#Family_environment http://en.wikipedia.org/wiki/Inheritance_of_intelligence#Fam...