Yes, that figures, but in no way explains entrenchment, as that happens on both sides. An example of the type of entrenchment I'm suggesting is the person who argues vehemently about the spelling of 'realize' when I say the the Canadian spelling is 'realise'. Obviously I accept both.
In politics, my father's claim was that a fencepost would win where we lived, if they ran it for a particular party. So it didn't matter how dumb the guy was, he'd always get in, because of entrenchment.
Interesting study, although it might be interesting to compare different countries and the brains of people who live under authoritarian political systems. How would they compare with the Democrats' and Republicans' brains in the U.S.?
My father and his side of the family were mostly Midwestern Republicans, while my mother and her side of the family were California Democrats (although my grandparents were Southern Democrats who moved to California and slowly "liberalized," more or less, while my mother and aunt were very staunch liberal Democrats). I think they might have been products of the time and place they were raised in, particularly as one starts to understand politics and formulates one's political values, influenced by any number of sources.
I recall a story from when I was a young kid, my older cousin was getting married to young man with long hair and was one of them liberal hippie types. I had an uncle (a decorated WW2 vet) who boycotted the wedding. He wasn't happy about it at all. That might be a case of "entrenchment," although he kind of mellowed out over the years, at least about the long hair.
The liberal anti-war sentiment of the 60s also faded away and gave way to Ronald Reagan's militaristic capitalism. It would appear that some of those who may have been anti-war in the 60s might have modified their views by the 1980s. Or maybe the pro-war crowd was so heavily entrenched that they outlasted the other side.
Another thing that I've observed during my life is that, with some, there's a certain amount of peer pressure one can discern among people who are, more or less, on the same side.