Under the watch of the experimenter, the volunteer—dubbed “the teacher”—would read out strings of words to his partner, “the learner,” who was hooked up to an electric-shock machine in the other room. Each time the learner made a mistake in repeating the words, the teacher was to deliver a shock of increasing intensity, starting at 15 volts (labeled “slight shock” on the machine) and going all the way up to 450 volts (“Danger: severe shock”).