Copycats and Contrarians takes on the idea, promulgated by some economists, that humans are selfish and independently-minded creatures, who use complex mathematical rules to solve problems. This book argues that we are also social animals, and our instincts to follow, herd, and copy others are deeply ingrained.So, is herding mindless and stupid? When we suspect that people around us know more than we do, then following them is common sense. We may join long restaurant queues but avoid empty restaurants. Social media reviews may help us to choose our holidays. Policy-makers, who release social information about others’ choices, may encourage us to be more responsible about everything from energy consumption to organ donation.But imitation is also the product of ancient impulses and instincts. It evolved in our ancestors, enabling them to survive harsh natural environments. When food and resources were scarce and threats were ever-present, our ancestors followed others around them because they might have had better information about where to find food or water. Or, as part of a group, they would find safety from predators and environmental threats. Over the course of human history, however, civilizations have grown, technologies have become ever more sophisticated, and our herding tendencies now seem more maladaptive than effective survival strategies.Copycats and Contrarians explores how, today, we face a delicate, fragile balance of individual, group, and social interests. In the modern world, following others sometimes works well. But other times it generates perversions. The Internet has given mob-leaders a power to manipulate crowds that is unrivalled in human history. The political tensions around the UK’s vote to leave the EU and the US election of Donald Trump have both been driven by rapid shifts in herd opinions. These shifts are catalyzed by online gossip, twitter trolls, and false news that speed along globalized social media channels. In computerized financial markets, too, herding develops quickly and precipitates large and destabilizing speculative bubbles, including flash crashes on futures and currency exchanges.