When behavioural scientist Dr Pragya Agarwal moved from Delhi to York more than 20 years ago, her first priority was to blend in. As a single parent, a woman of colour and an academic, she worked hard to “water down” the things that made her different from those around her. Yet the more she tried to fit in, the more Agarwal began to ask herself why humans appear programmed to create “in groups” and distrust those on the outside.