In teh netz delightful webby way, i came across this site today:
In a large sample of young adults, we related self-reported political attitudes to gray matter volume using structural MRI. We found that greater liberalism was associated with increased gray matter volume in the anterior cingulate cortex, whereas greater conservatism was associated with increased volume of the right amygdala.
anterior cingylate cortex -- a gray matter of the brain associated with understanding complexity
right amygdala -- an almond-shaped area that is associated with fear and anxiety