What causes addiction? Easy, right? Drugs cause addiction. But maybe it is not that simple. This video, made by Kurzgesagt, is adapted from Johann Hari's New York Times best-selling book 'Chasing The Scream: The First and Last Days of the War on Drugs.' The video highlights the important work of Dr. Bruce Alexander and his Rat Park project, a groundbreaking study into the causes of drug addiction.