Cass Sunstein

To become an extremist, hang around with people you agree with

Cass Sunstein — co-author of the hugely influential Nudge and an adviser to President Obama — unveils his new theory of ‘group polarisation’, and explains why, when like-minded people spend time with each other, their views become not only more confident but more extreme What explains the rise of fascism in the 1930s? The emergence