Long time ago I read that the correlation between big head and gt is quite small. Here we go, I found the book.
Head size correlates 0.14 with IQ. (One would be a perfect correspondence between head size and IQ, zero would indicate no relationship whatsoever)
DS6 has a huge head in the 99%+. We got to the point that I had to take him back for repeated measurements to make sure he didn't have hydrocephalus. When DS4 got to that point, I was just told, "He is like his brother. It's genetic"
DS4's head was a little bit smaller though but still easily in the upper 90%.
