The Milgram Experiment was an experiment in social psychology named after Dr. Stanley Milgram, the Yale professor who was the creator and executor of the experiment. It is taught in most introductory Psychology classes for two reasons: debate on medical ethics and as an example of the human tendency to obey orders. When the experiment was executed, it sparked debate about acceptable stress to place on people in psychological experiments, and introduced the idea of informed consent into medical ethics.
The Milgram Experiment explored how people behaved when under instructions from an authority figure that contradicted moral codes. In the experiment, for which subjects were recruited by a classified ad offering them $4.50 for one hour of time, a subject was taken into the laboratory and was met with the person executing the experiment (an actor, not Dr. Milgram), and a person who claims to be another person who responded to the ad but was in fact an actor. The "experimenter" claimed that the experiment was a study on the effects of punishment on learning, and that one subject would serve as teacher while the other was the learner. At this point, two slips of paper were drawn. Both were labeled "teacher". The actor playing a subject acted as if his read "learner"; for obvious reasons, the actual subject took the role of teacher.
At this point in the experiment, the actor was strapped into a chair and his wrists were fitted with electrodes. The experimenter informed the subject (and the actor) that the straps were to prevent excessive movement when the learner is shocked and the paste applied along with the electrodes is to prevent blisters and burns. At this point, the actor expresses apprehension, and claims to have a heart condition.
The subject was then taken, with the experimenter, to a separate room. The subject's job was to read off questions from a verbal memory test, and give an electric shock by flipping the next switch on the panel, labeled "SHOCK GENERATOR" in front of xir. The thirty switches were labeled in increments of 15 volts, from 15 to 450 volts. The 15-volt switch was labeled "Slight shock", the 420-volt switch was labeled "DANGER: Severe shock", while the final two switches had the ominous label of only "XXX".
As the experiment began, the actor playing the learner was to make frequent mistakes. The first four shocks were taken silently, but a groan was heard at 75 volts; his protests were more extreme at further shocks. (Please note that, as should be obvious, the actor was not actually being shocked, but was merely giving a scripted response at each level. The switches actually turned on a light bulb as notification to the learner.) At 150 volts, the actor yelled, "Experimenter, get me out of here! I won't be in this experiment any longer! I refuse to go on!" 180 volts receives "I can't stand the pain!" By 270 volts, each shock is met with a scream; at 300 volts, he shouts, in desperation, that he will not give answers to the memory test. The experimenter would then inform the subject that a nonresponse was to be treated as a wrong answer, and the experiment was to continue. Subsequent questions were, indeed, not answered. At 315 and 330 volts, the learner screamed violently.
345 volts brought the most terrifying development of all: silence. The learner, at this point, responds to neither the questions nor the shock. The experimenter insists that the experiment be brought to its conclusion.
Should the subject request to stop, a set of rehearsed prompts were given firmly in a pre-set order. If all the prompts were exhausted, the experiment was stopped. (The subject was still paid for xir time; this was stated at the beginning of the experiment that the pay would happen either way. In any event, five dollars is hardly worth killing someone over.) The first response was "Please continue." The next protest was met with "The experiment requires that you continue." The third response was "It is absolutely essential that you continue." The fourth was "You have no other choice; you must go on." A fifth refusal would stop the experiment.
When the experiment was stopped, the subject was informed the true nature of the experiment, and the "learner" was revealed to be no worse for the wear and to bear the subject no ill will. The subject was shown that xe indeed had not killed anybody and, once the experiment was concluded, given the results.
The results were shocking. 65% of subjects studied completed the experiment, giving the learner the strongest shock listed. None stopped before 300 volts. Almost all requested to stop the experiment previously. All subjects showed signs of great tension- for example, sweating and nervous tics- but most went on. This result was surprising. The experimenter was selected to be a person not physically intimidating, did not stand between the door and the subject, and made no aggressive gestures. As the subjects had received their money, they had no logical reason to continue.
The experiment was a striking example of the essentially obedient nature of humans. This is the sort of obedience that leads to mass atrocities; the Nazis are an example. Other possible explanations, most notably the priority people give to science, exist for the outcome of this experiment, but further experiments showed a general trait of obedience to an authority figure tended to, in general, override personal morals.
Dr. Milgram executed further experiments in the same vein after the surprising result of this first one. The variants included having the learner in the same room as the teacher, requiring the teacher to physically place the hand of the learner on a shock plate, and having the experimenter in a different room. All of them resulted in drastically fewer people completing the series; the lowest percentage occurred in the latter of these.
Another experiment conducted was what would happen if the subject was working alongside yet another actor, also working in the teacher role. In this variant of the experiment, the subject was to alternate question-reads, and then switch-flips when appropriate, with this actor. The question was what would happen when the companion continued the experiment, and what happened when the companion stopped. When the companion did not object, an incredible 95% of subjects continued the experiment to the end; equally strikingly, only 10% completed the experiment when the companion refused to continue.
The experiment also had another side effect: extreme critique of the ethics involved. Today's doctrines of informed consent would make it extremely difficult to conduct a similar experiment, and the experiment as Milgram executed it would never be approved. Present-day ethical review boards would not allow leading a person to believe that xe might have killed a man in a psychology experiment.
The critics had reason to complain. A direct quote from Milgram's initial report: "I observed a mature and initially poised businessman enter the laboratory smiling and confident. Within 20 minutes he was reduced to a twitching, stuttering wreck, who was rapidly approaching a point of nervous collapse." This level of stress in a subject would halt an experiment immediately if it were to occur in one executed now. Milgram's efforts to ensure the subjects were, at the end, comforted to know that they hurt nobody, reminded how they objected, and were informed that most people completed the series, would not be considered sufficient counterbalance for the stress.
Even though the experiment would not be approved in the present day, it gave very valuable results. It has helped explain mass atrocities in history, such as, as mentioned previously, the Holocaust. Although there are many significant differences between the situations, most notably the temporary nature of the experiment and the very artificial situation the subjects were in, it still seems to be a very valid explanation.
References: My Intro to Psychology class, and its textbook (Psychology 4th edition, by Peter Gray). Only direct quotes from the experiment were directly copied. Information on the Milgram Experiment, in that book, begins on page 554.