Humans everywhere divide the world into "us" and "them."
Why are we so tribal?
This article and its 'research' is 100% bullsh*t.
Reason -- it was done by Psychologists, who aren't even real doctors. Yet they act is if they are one. [Psychologists were students who flunked out of J-School.(1)]
And Psychiatrists aren't much better. They're Doctors who couldn't stand the sight of blood in medical School. On the upside, at least they can write you an Rx for some cool drugs ;-)
(1) oh ... wait ... that's my 'tribal prejudice' showing. Shame on me.