As to the “exception to the rule” thing one comment. I find these studies interesting certainly, but mostly in the academic sense. The things that influence intelligence are many; genetics (the vast majority of which is unknown) general health, socioeconomic background of the parents, socioeconomic situation as a child, level of stimulation in early childhood….the list goes on and on. It simply stands to reason that something as complex as intelligence would be influenced by many things. Additionally, I.Q testing is rarely totally without bias towards regular education. It’s exceedingly hard to measure certain types of intelligence if the subject, for instance, doesn’t know how to read.

Again, studies in intelligence are fine and interesting, but no single one can be taken alone. Otherwise, you’re going to find a gazillion exceptions to every “rule”.