Dividing people into groups is part of our social experience. Be it through race, gender, nationality; we build our identities through groups we belong to. And these identities can be numerous and elastic. But, what makes us decide who is like us and who is the other? In this week’s Why Factor, Sandra Kanthal asks; why do we divide the world into us and them?

(Image: Baseball caps, Credit: Sandra Kanthal/BBC)