When high speed internet became widely available a few years ago, growing numbers of people began to worry that their porn use was running out of control. Far from preparing them for fulfilling relationships, viewing an endless stream of porn videos led to unexpected symptoms. Perhaps most surprisingly, for the first time in history erectile dysfunction was becoming a significant problem for young men. This led to one of the largest informal experiments in the history of science. Tens of thousands of people have tried abstaining from sexually stimulating material in a process they call 'rebooting'. Many of them reported startling changes, from improved concentration and elevated mood to a greater capacity for real-life intimacy.

Gary Wilson has listened to the stories of those who have tried giving up internet porn and related them to an account of how the reward system of the brain interacts with its environment. And now a growing body of research in neuroscience is confirming what these pioneers have discovered for themselves - internet pornography can be seriously addictive and damaging.