well, most people nowadays believe that the brain is the source of our "personality", so it's not big news that brain structure is related to personality traits, and vice versa. and we've known for years that the amygdala is involved with emotional stuff, so big deal, basically. find me a difference in brain structure between yankees fans and red sox fans, and i'll pay attention.

and it's not clear that looking at differences in developing brains gives you a window into differences between adults. kids all develop at their own paces; maybe every adult amygdala is more alike and adult aggression is completely unrelated. so this might be useful in child development psych, but not necessarily to explain the war president.

"find me a difference in brain structure between yankees fans and red sox fans, and i'll pay attention. "

Simple, yankees fans have bigger brains.

Yeah but the difference between the pea and the thimble that is the maxium volume of any pro sports fan isn't meaningful when it comes to demonstrating that the difference between them and apes is intelligence.