Traditionally, the study of international relations has been about institutions, not individuals and the psychology that motivates them. But that is changing. Rose McDermott, professor of international relations at Brown University, introduces the work of Robert Jarvis and others pioneering the field of ‘political psychology.’

Putting people and things into categories is something we all do. It’s a useful shortcut but reveals biases. And it plays a role in everything from ethnic violence to childhood development, as psychologist Susan Gelman explains.