We like to believe that only a few bad apples spoil the virtuous rest of humanity.

The famous  Stanford prison experiment, conducted in 1971 by a team of researchers led by psychology professor Philip Zimbardo, will challenge this belief by suggesting that "the rest of humanity" could possibly not be as virtuous as expected.

Zimbardo idea was simple: he wanted to study ordinary people's behaviors in an extraordinary environment, in a prison.

He asked twenty-four male students ―in good mental and physical health― to take on randomly assigned roles of prisoners and guards in a mock prison situated in the basement of the Stanford psychology building.

The participants will quickly exceed what was planned: one-third of the guards exhibited authoritarian behaviors and almost all prisoners accepted the humiliating treatments.

The dramatic turn that the experiment will take will force Philip Zimbardo to end the experiment after six days, 11 days sooner than initially planned! 

The results will be interpreted in terms of the most popular view of human nature in the 70ies: the Blank Slate and its motto: "there are no such things as human nature, it's societies that pervert humans". A minority will analyze the experience in completely different terms. They will interpret the results as a concrete manifestation of innate traits, of a human nature that has limited social skills.

Despite these different interpretations, everyone will agree to recognize the results as an argument to demonstrate the impressionability and obedience bias of humans in the presence of an ideology legitimated by institutional supports. These biases were also highlighted in the Milgram experiment.


The experience of Stanford Prison poses crucial questions about the origin of good and evil: is it innate to do good? Does evil come from an innocent, virtuous human nature that is perverted by events/society? And what if we would have to learn to do good? And what if to do good in such circumstances was complicated and required complex abilities?


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