Rigidity at the neural level breeds rigidity at the civic level. Economists studying East Germany, including Harvard’s Alberto Alesina, found that decades of socialist rule left scars on behavior: Citizens became more cautious, less entrepreneurial, and slower to trust. A society that punished initiative and rewarded conformity trained its population to avoid novelty. Those scars of enforced consensus outlasted the Berlin Wall. Neuroscience also shows that cognitive flexibility isn’t automatic. Like any skill, it must be trained. In a paper titled “One cannot simply ‘be flexible,’ ” Ghent University cognitive scientist Senne Braem and colleagues showed that when people are...