In 1971 psychologists created one of the most important experiments in the history of psychology.
The experiment, known as the Stanford Prison Experiment, looked at the impact of situations on human behavior.
The researchers, led by Philip Zimbardo, wanted to know how situations could affect how people behave.
In particular, they wanted to know if good people would change their personalities and lose their values.
In the experiment, participants were divided into two groups.
One group became prison guards and the other group became prison inmates.
The experiment was set up in Stanford University’s psychology building.
A group of 24 students was chosen to play the roles, 12 guards and 12 prisoners.
The students came from a large group of volunteers who wanted to participate in a psychology experiment.
Those who were chosen had no criminal background and had no significant medical or psychological problems.
They agreed to participate in the experiment for one to two-week period.
It was? one of the most important experiments in the history of psychology.
（The experiment was scheduled to last one to two weeks.）
（The prisoners had to remain in prison for the duration of the experiment.）
（To isolate someone，means to keep them apart from others.）
The prisoners had to remain in prison 24 hours a day during the experiment.
Guards worked in teams of three and were assigned to work in eight-hour shifts.
Unlike the prisoners, they were free to return to their homes between shifts.
Hidden cameras and microphones were used to observe the behaviors of both the prisoners and guards.
The simulated prison included three small prison cells, 6 feet by 9 feet.
Each cell had three small beds and held three prisoners.
There was also a closet that served as a solitary confinement room.
This was used to isolate prisoners who needed to be punished for bad behavior.
Guards were instructed not to physically harm the prisoners in any way.
Prisoners were to be addressed by their assigned numbers and never by name.
To prevent eye contact with the prisoners, guards wore mirrored sunglasses.
This was done to dehumanize the relationship between guards and prisoners.
（To physically harm someone means to physically hurt them.）
（The prisoners had to remain in prison for the duration of the experiment.）
（To isolate someone means to keep them apart from others.）
