Steven Pinker may be the world’s best-known cognitive psychologist, a public intellectual who for decades has used his fame to help us understand how we think, how we develop language, and how our behaviour is shaped by evolution and biology.He’s a professor of Psychology at Harvard and his most recent book is a hugely entertaining reflection on social norms, cooperation, outrage cycles, social media pile-ons, sudden political shifts, and moral panics. It’s called When Everyone Knows That Everyone Knows, and Pinker joins Josh to discuss echo chambers, status hierarchies, and the corrosion of common ground.