“The Stanford Prison Experiment” combines historical accuracy and riveting entertainment, although contemporary audiences might have a difficult time understanding how a team of U.S. researchers could allow a handful of students to terrorize and dehumanize each other for a couple of weeks in August 1971. At least without doing prison time themselves.

Opening on the selection process heaves the viewer into the action and emphasizes how normal the subjects are and how things could spiral out of control so quickly. Researchers led by Philip Zimbardo (Billy Crudup) ask the candidates questions whose only validity seems to be to ensure that they aren’t violent people, and most importantly do not think themselves violent. That’s what makes their almost immediate transformation into violent people, increasingly bizarre and amoral, so jarring.

It happens as soon as the prisoners and guards put on their respective uniforms. The way they take on their roles would be comical if it weren’t so uncomfortable to watch. Actor Michael Angarano’s character is particularly sadistic as a guard leader, although it might be lost on younger viewers that his character is mimicking the portrayal of another movie guard in “Cool Hand Luke.” That really happened, as did the more peculiar acts such as feminizing prisoners and making them act out scenes from old horror movies.

The film doesn’t just re-create the history. Also it ends up explaining to a degree how both guards and prisoners got lost in their jobs, believing in what they were doing and becoming absorbed in their unreal temporal and physical reality. The movie looks long on paper but is engrossing and goes by fast. The coda, after the experiment is hastily scotched lest worse things happen, is fascinating.

“The Stanford Prison Experiment,” available through on demand rental services, is a must-see film that leaves the viewer shaken and disturbed, which it should do. (R) 122 min.