Imagine a concrete room, not much bigger than a parking space. You're in there 23 hours a day, 7 days a week. This is the reality of solitary confinement at prisons across the United States. Keramet Reiter, a criminology professor at UC Irvine, says that while some inmates in solitary are dangerous, others are there because they're difficult for prisons to manage, or because of bureaucratic inertia. This week on Hidden Brain, we look at what happens in solitary confinement, and the psychological effects of being alone for long periods of time.