"Why we run with—or avoid—the crowd, and why it matters, from choosing a restaurant in a tourist trap to believing fake news. I learned a lot" (Tim Harford, author of The Undercover Economist ). Rioting teenagers, tumbling stock markets, and the spread of religious terrorism appear to have little in common, but all are driven by the same basic instincts: the tendency to herd, follow, and imitate others. In today's interconnected world, group choices all too often seem maladaptive. With unprecedented speed, information—or misinformation—flashes across the globe and drives rapid shifts in group opinion. Adverse results can include speculative economic bubbles, irrational denigration of scientists and other experts, seismic political reversals, and more. Drawing on insights from across the social, behavioral, and natural sciences, Michelle Baddeley explores contexts in which behavior is driven by the herd. She analyzes the rational vs. nonrational and cognitive vs. emotional forces involved, and she investigates why herding only sometimes works out well. With new perspectives on followers, leaders, and the pros and cons of herd behavior, Baddeley shines vivid light on human behavior in the context of our ever-more-connected world. "Her observations on how both risk-taking and conformism contributed to Donald Trump's election, and on how social media affects 'copycats,' make for a well-timed and valuable study." — Publishers Weekly "This might well become the defining book, for this decade and more, on the topic of herding and social influence." —Cass Sunstein, co-author of Nudge