While watching some videos on YouTube, one of the related links showed up as Stanford Prison Experiment - Psychology of imprisonment. I watched it, and it ended up being quite fascinating. There is a Wikipedia link here, and the videos are below:
Part 1
Part 2
Part 3
Part 4
Part 5
Each part is just under 10 minutes long. The experiment, done in 1971, which was to have lasted two weeks, ended up finishing after only six days. The volunteers who were either guards or prisoners fell into their roles so well, the ‘prison’ went into a state of chaos. Riots, punishments, solitary confinement, two prisoners having breakdowns and having to be removed - all in just six days. Quite eye-opening viewing - I don’t know how anyone could survive in a real prison, as either an inmate or a guard, without some sort of emotional scarring.