It was in 1968, the day after the assassination of civil rights leader Martin Luther King. Jane Elliot, a teacher in a small town of Iowa, decided to demonstrate to her class what prejudice was about. Jane asked her class whether they knew how it would feel to be judged by the colour of their skin. The students mostly thought they could. But she wasn’t so sure, so she launched what was destined to become a famous experiment.

One of the most important things we learn as humans is perspective-taking. And children don’t typically get a meaningful exercise in that. When one is forced to understand what it’s like to stand in someone else’s shoes, it opens up new cognitive pathways.

The brilliance of the blue eyes/brown eyes exercise was that Jane Elliot switched which group was on top. That allowed the children to extract a larger lesson: systems of rules can be arbitrary. The children learned that the truths of the world aren’t fixed, and moreover they’re not necessarily truths.

Education plays a key role in preventing genocide. Only by understanding the neural drive to form ingroups and outgroups – and the standard tricks by which propaganda plugs into the drive – can we hope to interrupt the paths of dehumanization that end in mass atrocity.