Writer Julia Galef talks to Tim Harford about the role of numbers in helping us think more rationally, and what Star Trek’s Mr Spock can teach us about making predictions. Julia is author of The Scout Mindset, a book about how our attempts to be rational are often clouded or derailed by our human impulses, and the ways we can avoid these traps. Producer: Nathan Gower (Image: Leonard Nimoy as Mr Spock. Credit: Bettmann/Contributor via Getty Images)