Most of us have struggled to understand how seemingly ordinary people can sometimes do morally questionable things.
Two years ago, the photos of young American soldiers smiling while torturing Iraqi prisoners at Abu Ghraib horrified the world and raised the question of who was to blame.
Some of the soldiers defended themselves by claiming they were just doing what their superiors had instructed. But the smiling faces in the photos seemed to imply that they followed the orders without protest.
Are those soldiers inherently bad people? Or is it more complex than that? Do you have to be an evil person to do evil things?
In 1961, social psychologist Stanley Milgram asked those same questions. That was the year Nazi Adolf Eichmann, on trial for his war crimes, denied responsibility for his actions by saying he was simply doing what his superiors told him to do.
Contemplating this rationalization, Milgram came up with a famous and controversial experiment to examine what happens when ordinary people are faced with morally questionable orders. What he learned shocked not only him but the entire world.
In the experiment, conducted at Yale University over a period of months in 1961, an authority figure -- "the experimenter" -- dressed in a white lab coat and instructed participants to administer what they believed were increasingly painful electric shocks to another person.
Although no one was actually receiving shocks, the participants heard a man screaming in pain and protest, eventually pleading to be released from the experiment. When the subjects questioned the experimenter about what was happening, they were told they must continue.
And continue they did: Two-thirds of Milgram's participants delivered shocks as they heard cries of pain, signs of heart trouble, and then finally -- and most frightening -- nothing at all.
The response to the experiment was enormous, and in 1975, strict guidelines about regarding psychological experiments on humans shelved any further potential replications. Since then, scientists have been stymied in efforts to replicate Milgram's study.
"Primetime" wanted to know if ordinary people today would still follow orders, even if they believed their actions were causing someone else pain. Would as many follow the seemingly dangerous and painful orders as in the original experiment? After contacting respected psychologist Jerry Burger at Santa Clara University in California, ABC News was able to replicate Milgram's study in a modified way.
After the American Psychological Association provided feedback on the testing protocol, this collaboration between "Primetime" and Santa Clara University marks the first time in decades that the famous study has been re-created.
Burger said, "People have often asked the question, 'Would we find these kinds of results today?' and some people try to dismiss the Milgram findings by saying, 'That's something that happened back in the '60s. People aren't like that anymore.'"
After placing an ad in the paper looking for participants for "a learning and memory study" and putting the respondents through psychological screening, "Primetime" found 70 people lined up for the experiment.