The Milgram experiment, held at Yale University in 1961, is a famous psychological experiment conducted by Stanley Milgram. It appeared to demonstrate that average people would willingly obey orders from people in positions of authority (such as, in that case, a scientist in a white lab coat), even to the point that it involved inflicting life-threatening harm on other people.
In the 1960s, when the anti-establishment movement was in its heyday and university ethics regulations were notably more lax than they are today, a number of significant psychology experiments were conducted centering around questions of authority and group conformity. There was obvious interest to the new generation of counterculture radicals, but the immediate context also involved something more disturbing: why, asked these psychologists, had so many people gone along with the murderous schemes of the Nazi regime in Germany during the 1930s and early 1940s? Presumably they were not (or rather, not all) Nazis - so why had so many apparent non-Nazis willingly participated in the most horrific crimes of the century?
Stanley Milgram thought he had an answer: they were culturally disposed to obey people in authority, even if those in authority were giving obscenely immoral commands. Milgram was, at the time, a young Jewish psychologist, who later went on to tech at the City University of New York after being denied tenure at Harvard University. In the eponymous study now known simply as the Milgram experiment, Milgram assembled test subjects in pairs and then divided - or at least appeared to divide - each pair into a "teacher" and a "student." They were then taken into adjacent rooms, and the teacher was given a set of simple lessons (matching word pairs) to teach the student. Any time the student got an answer wrong, the teacher was instructed, he must push a button delivering an electric shock. The shocks started small, at 30 volts, but progressed upwards from 450 volts. Subjects were led to believe this was an experiment in educational psychology.
In reality it was something quite different. The only true subjects were the teachers: the learner, in each case, was an actor. Before they parted, the actor mentioned in passing that he had a heart condition. Afterwards, he did not receive any electric shocks - but, as the shocks increased in supposed intensity, he did begin showing signs of extreme pain, including crying out in pain and banging on the wall. Eventually, he would fall silent, which - given previous pain and knowledge about his heart condition, would suggest a medical emergency.
Stunningly, of Milgram's 40 research subjects, 20 were willing to give the full 450-volt dose, despite all of the above, and despite the fact that this "experiment" involved intentionally inflicting pain on another human being through electric shocks. None of them did so without expressing at least some discomfort, but other than those who walked away early on, all were apparently willing to continue provided that they were ordered to do so by a scientist, and reassured that responsibility for the experiment rested with the scientist and not with themselves. Only 1 of 40 participants refused to administer shocks below 300 volts. Even those who did refuse to continue do not appear to have made serious attempts to stop the entire experiment.
What this experiment really reveals has been controversial. There have been some doubts that Milgram's results are reproducible. To the extent that the experimental results are valid, however, they reveal some very disturbing things about human psychology. A decade later, an even more extreme experiment was conducted on the other side of the country, but with a similar theme: the Stanford Prison Experiment.