For Democrats, the region of the brain with the most activity was the left posterior insula, a region that is associated with processing emotions and understanding what other people are thinking or feeling. The region is sometimes called the "theory of the mind," and it's the part of one's brain that allows you to estimate, for example, what your friend, partner or even a stranger may be thinking by imagining yourself in their shoes, so to speak. (No word yet on whether woman's brains have vastly more developed "theory of the mind" regions.) It's a region that's associated with empathy and the understanding that each person has their own unique point of view.

For Republicans, the region of the brain that was most active during risky behavior was the right amygdala. This region of the brain is primarily responsible for producing fear, although it can also create anticipation of reward. It's the part of the brain that teenagers often rely on to make decisions, one of the reasons that teens are more impulsive and aggressive than adults. The larger role of the amygdala in teenage brains -- a role that diminishes as people reach their mid-20s -- is one of the justifications for laws that prohibit people from drinking alcohol and doing other things until their early to mid-20s. (Apparently the U.S. military still doesn't care whether its soldiers have brains that are able to mitigate impulsivity and aggression.) This higher level of activity in the amygdala in Republican brains is something that scientists have observed before, although not directly in this risk environment.