Stanley Milgram, a psychologist at Yale University, conducted a study focusing on the conflict between obedience to authority and personal conscience. He examined justifications for acts of genocide offered by those accused at the World War II, Nuremberg War Crimes trials. Their defence often was based on "obedience" - - that they were just obeying orders whilst under the authority of their superiors.

The experiment began in July 1961, a year after the trial of Adolf Eichmann in Jerusalem. Milgram devised the experiment to answer the question "Could it be that Eichmann, and his million accomplices in the Holocaust were just following orders? Could we call them all accomplices?"

The results of the study were made known in Milgram's Obedience to Authority: An Experimental View (1974).

So-called "teachers" (who were actually the unknowing subjects of the experiment) were recruited by Milgram in response to a newspaper ad offering $4.50 for one hour's work. Individual subjects thus recruited turned up to take part in a Psychology experiment investigating memory and learning at Linsly-Chittenden Hall on Yale University's old campus. He or she was introduced to a stern looking experimenter in a white coat and to a rather pleasant and friendly co-subject who was also presumably recruited via the newspaper ad. The experimenter explained that one subject would be assigned the role of "teacher" and the other would be assigned the role of "learner."

Two slips of paper marked "teacher" were handed to the subject and to the co-subject. The co-subject was actually an actor who, in posing as a subject to the experiment, subsequently claimed that his slip said "learner" such that the unknowing subject was inevitably led to believe that his role as "teacher" had been chosen randomly.
Both learner and teacher were then given a sample 45-volt electric shock from an apparatus attached to a chair into which the "actor-learner" was to be strapped. The fictitious story given to the "teachers" was that the experiment was intended to explore the effects of punishment for incorrect responses on learning behavior.

A succession of unknowing subjects in their roles as teacher were given simple memory tasks in the form of reading lists of two word pairs and asking the "learner" to read them back and were instructed to administer a shock by pressing a button each time the learner made a mistake. It was understood that the electric shocks were to be of increased by 15 volts in intensity for each mistake the "learner" made during the experiment.

The shock generator that the "teacher" was told to operate had 30 switches in 15 volt increments, each switch was labeled with a voltage ranging from 15 up to 450 volts. Each switch also had a rating, ranging from "slight shock" to "danger: severe shock". The final two switches being labeled "XXX". The experiment was conducted in a scenario where the "learner" was in another room but the "teacher" was made aware of the "actor-learner's" discomfort by poundings on the wall.
No further shocks were actually delivered - the "teacher" was not aware that the "learner" in the study was actually an actor who was intended, by the requirements of the experiment, to use his talents to indicate increasing levels of discomfort as the "teacher" administered increasingly severe electric shocks in response to the mistakes made by the "learner".

The experimenter was present in the same room as the "teacher" and whenever "teachers" asked whether increased shocks should be given he or she was verbally encouraged by the experimenter to continue. In this scenario 65% of the "teachers" obeyed orders to punish the learner to the very end of the 450-volt scale! No subject stopped before reaching 300 volts!

At times, the worried "teachers" questioned the experimenter, asking who was responsible for any harmful effects resulting from shocking the learner at such a high level. Upon receiving the answer that the experimenter assumed full responsibility, teachers seemed to accept the response and continue shocking, even though some were obviously extremely uncomfortable in doing so.

In an article entitled "The Perils of Obedience" (1974) Stanley Milgram wrote:-
"Before the experiments, I sought predictions about the outcome from various kinds of people -- psychiatrists, college sophomores, middle-class adults, graduate students and faculty in the behavioral sciences. With remarkable similarity, they predicted that virtually all the subjects would refuse to obey the experimenter. The psychiatrist, specifically, predicted that most subjects would not go beyond 150 volts, when the victim makes his first explicit demand to be freed. They expected that only 4 percent would reach 300 volts, and that only a pathological fringe of about one in a thousand would administer the highest shock on the board".

The Obedience to Authority experiment was continued by Milgram over a number of other scenarios such as where the "learner" could indicate discomfort by way of voice feedback - at "150 volts", the "actor-learner" requested that the experiment end, and was consistently told by the experimenter that - "The experiment requires that you continue. Please go on." or similar words. In this scenarion the percentage of subjects who were prepared to administer the maximum 450 volts dropped slightly to 62.5%


Where the experiment was conducted in a nondescript office building rather than within the walls of a prestigiously ornate hall on Yale's old campus the percentage of subjects who were prepared to administer the maximum voltage dropped to 47.5%.

Where the "teacher" had to physically place the "learner's" hand on a "shock plate" in order to give him shocks above 150 volts the percentage of subjects who were prepared to administer the maximum voltage dropped to 30.0% and where the "experimenter" was at end of a phone line rather than being in the same room the percentage of subjects who were prepared to administer 450 volts dropped to 20.5% and where the "teacher" could himself nominate the shock level the percentage of subjects who were prepared to continue to the end of the scale dropped to 2.5%

Milgram summed up his findings in relation to the main experiment in "The Perils of Obedience" (1974):-
"The legal and philosophic aspects of obedience are of enormous import, but they say very little about how most people behave in concrete situations. I set up a simple experiment at Yale University to test how much pain an ordinary citizen would inflict on another person simply because he was ordered to by an experimental scientist. Stark authority was pitted against the subjects' strongest moral imperatives against hurting others, and, with the subjects' ears ringing with the screams of the victims, authority won more often than not. The extreme willingness of adults to go to almost any lengths on the command of an authority constitutes the chief finding of the study and the fact most urgently demanding explanation."

The experiment has been repeated by other psychologists around the world with similar results. Variations have been performed to test for variables in the experimental setup. For example, subjects are much more likely to be obedient when the experimenter is physically present than when the instructions are given over telephone.