Why do good people so often do nothing when a small intervention could make a big difference? Pioneering psychologist Catherine Sanderson demystifies the mindset of bullies and bystanders to show why courage comes at such a high cost, and how we can learn to be brave. We are bombarded every day by reports of bad behaviour: from sexual harassment to political corruption, from bullying to corporate greed. We believe these things are wrong or even evil, but in practice few of us choose to intercede.The Bystander Effect draws on the latest developments in psychology and neuroscience to explain why we act differently in groups than when we are alone; how slippery slopes begin and prosper; and where the dissonance lies between good intentions and real action.Sanderson answers the question of why otherwise good people can become bystanders to evil of any scale, and gives practical strategies for how to resist pressures and make change in our own lives.Courage, this book shows, is not a virtue we're born with or without. A bystander can learn to be brave.