The URL, below, is for a statement in 2010 from University College London (“UCL”) on the finding by UCL scientists (borne out, before and since, in other experiments) that political orientation on either side of the present political and cultural chasm can actually be detected in the physical structure of the brain, using an ordinary MRI:
https://www.ucl.ac.uk/news/2010/dec/left-wing-or-right-wing-its-written-brain
In the UCL experiment the subjects were asked to declare their own political orientation, on a scale that ran from very liberal to very conservative. After that, the subjects were given an MRI scan, whose results corresponded to their prior self-declarations with more than 80% accuracy.
The basic correlations found were (a) between liberalism and a larger anterior cingulate cortex; and (b) between conservatism and a larger right amygdala. As the UCL statement puts it:
“People with liberal views tended to have increased grey matter in the anterior cingulated cortex, a region of the brain linked to decision-making, in particular when conflicting information is being presented. Previous research showed that electrical potentials recorded from this region during a task that involves responding to conflicting information were bigger in people who were more liberal or left wing than people who were more conservative.
“Conservatives, meanwhile, found increased grey matter in the [right] amygdala, an area of the brain associated with processing emotion. This difference is consistent with studies which show that people who consider themselves to be conservative respond to threatening situations with more aggression than do liberals and are more sensitive to threatening facial expressions.”
There’s no shortage of other scholarly material available online about the functions of the amygdala (left and right) and more generally the so-called “reptilian brain” of which it’s a part.
I wonder whether how the “brain drain” of the last 60 years from Red State America to the major cities and university towns affects this. Meritocrats, after all, generally seek out other meritocrats in marriage, and the effect may be, over successive generations, to accentuate still more their characteristic brain structure.
For the highly negative effects of such polarization on those left behind, and therefore on society as a whole, see Michael Young’s prescient book, The Rise of the Meritocracy (1958).