Illustration of the setup of a Milgram experiment. The experimenter (E) convinces the subject ("Teacher" T) to give what he believes are painful electric shocks to another subject, who is actually an actor ("Learner" L). Many subjects continued to give shocks despite pleas of mercy from the actors.
https://commons.wikimedia.org/wiki/File:Milgram_experiment_v2.svg
https://creativecommons.org/licenses/by-sa/4.0/deed.en