Milgram's experiment is something that almost everyone has heard of at some point. It is the obedience to authority experiment. Milgram brought ordinary citizens into his lab and instructed them to administer what was thought to be painful electric shocks when the "learner" in the room failed at a simple memory task. Everything was fake, the electric shock machine, the people in the room, everything. Milgram was inspired by his reading of actions of Nazi concentration camp guards. He wanted to know if the tendency to obey authority was a general human trait or some specific feature of the German psyche.
The finding was that a majority of participants were willing to punish the learner and administer the "electric shocks."In an environment where the study participants feel less pressure to conform, the results would have differed.
When participants go into psychology experiments with a certain amount of skepticism about what the experimenter is up to, the experiment is not as valid and consistant. Their behavior in the experiment does not reflect what they would actually do in the real world.
Milgram claimed that about 75% of his participants believed the shocks were real, but another psychologists' re-analysis of the data showed that 2/3 of the people disobeyed the experimenter and only half of the people fully believed it was real. There is an argument that those who did administer the maximum amount of shock did so because they were sure that the experiment was fake.
Milgram was investigated byt he American Psychological Association for debriefing violations. He did not completely reveal the purpose of the study to his participants, nor did he really comfort the, about inflicting pain on another fellow human. Milgram also did not offer his participants an opportunity to opt out of the study, which is now a mandatory requirement of all human research.