What are some most shocking revelations of human study?

Looking back on human experiments over the years it is often the slightly unethical ones that shed the most light on human nature. Here are a couple of the most interesting:

Milgram’s Experiment:
Stanley Milgram conducted an experiment 1961 looking at human obedience to authority figures. The goal of his experiment was to find out how the German population in world war two could have gone along with Hitler’s ideas and orders. The results of the experiment were shocking.

Milgram experiment on obedience to authority figures:
The experiment consisted of scientist (S) running the experiment, a volunteer participant (W), and a confederate (fake participant that was actually part of the study) (V). Both the participant and the confederate started in a waiting room and drew slips of paper to determine which part of the experiment they would do. This part of the study, however, was fixed. Both slips of paper said teacher and the confederate would pretend that he got the role of the learner.

Once in the experiment the teacher (participant) was put in a separate room from the learner (confederate) and they were able to communicate over an intercom. The teacher would recite a list of words and have the learner recite them back. If the learner got the list wrong the teacher would push a button on a dashboard in front of him that would give the learner a shock. The shocks would get progressively stronger after every wrong answer until they got to a dangerous level as can be seen below.

Results:
The learner was a tape recorded dialogue that purposely got a certain amount of answers wrong to see if the teacher would continue to shock them. After a while the learner would start to complain about the shocks, say his heart was hurting, that he had a heart condition, and finally stop responding. The whole time the scientist running the experiment would urge the teacher to continue shocking the learner at higher and higher levels.
Before the experiment Milgram polled people asking how many teachers they thought would go to the maximum voltage. He found that people only thought on average that 1.2% of people would.
Milgram found that 65% (26 of 40) of participants administered the maximum voltage even after the learner had stopped responding. He further found that if there were other confederates in the room with the teacher rooting him on, the percentage rose to around 80%.
This was an incredible result showing how easily people will follow orders from authority even to the point of possibly killing someone.

Ethics:
This is one of the most commonly used examples of an unethical experiment because of the psychological stress it put on the participants.

http://en.wikipedia.org/wiki/Milgram_experiment

Stanford Prison Experiment:
Psychology professor Philip Zimbardo at Stanford University created a fake prison on the campus that he intended on having students run and occupy. He had Stanford student volunteer for the study and separated them at random into two groups. One of the groups the guards, the other the inmates.
Very quickly students adapted to their roles:

leading the officers to display authoritarian measures and ultimately to subject some of the prisoners to torture. In turn, many of the prisoners developed passive attitudes and accepted physical abuse, and, at the request of the guards, readily inflicted punishment on other prisoners who attempted to stop it. The experiment even affected Zimbardo himself, who, in his capacity as Prison Superintendent, lost sight of his role as psychologist and permitted the abuse to continue as though it were a real prison. Five of theprisoners were upset enough by the process to quit the experiment early, and the entire experiment was abruptly stopped after only six days. [1]

People’s positions of authority can greatly affect their demeanor and actions.
[1] http://en.wikipedia.org/wiki/Stanford_prison_experiment

This was an answer I wrote on Quora.