"At <a href=""https://www.youtube.com/watch?v=hppbxV9C63g&amp;t=2h10m00s"">2:10:00</a> I started wondering what if you compared the outcomes of adopted children compared to the biological children of successful parents? Are there any studies that make this comparison? Assuming that the parents treat the adopted and biological children with the same amount of care", I think finding differences here could be another important piece of evidence for the role that genetics play in the g-factor. Edit: I haven't finished the podcast yet so maybe they bring this up.,(reply>), There were indeed studies of that nature. As a whole they are refered to as "twin" studies where they specifically tested the iq of ttwins where one twin was adopted and the other raised by the biological parents. Long story short : upbringing does have a small effect but the vast majority of tested individuals were very close to the aggregate iq of their parents indicating that genetics is a far stronger predictor of iq than nurture.